diff --git a/llvm/test/Transforms/InstCombine/conditional-variable-length-signext-after-high-bit-extract.ll b/llvm/test/Transforms/InstCombine/conditional-variable-length-signext-after-high-bit-extract.ll
new file mode 100644
index 000000000000..70877dd526f4
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/conditional-variable-length-signext-after-high-bit-extract.ll
@@ -0,0 +1,1040 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt %s -instcombine -S | FileCheck %s
+
+; If we extract (via lshr) some high bits, and then perform their sign-extension
+; conditionally depending on whether the extracted value is negative or not
+; (i.e. interpreting the highest extracted bit, which was the original signbit
+; of the value from which we extracted as a signbit), then we should just
+; perform extraction via `ashr`.
+
+; Base patterns.
+
+declare void @use1(i1)
+declare void @use16(i16)
+declare void @use32(i32)
+declare void @use64(i64)
+
+define i32 @t0_notrunc_add(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @t0_notrunc_add(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @t1_notrunc_sub(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @t1_notrunc_sub(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[HIGHER_BIT_AFTER_SIGNBIT:%.*]] = shl i32 1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[HIGHER_BIT_AFTER_SIGNBIT]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGHER_BIT_AFTER_SIGNBIT]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = sub i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %higher_bit_after_signbit = shl i32 1, %nbits
+  %magic = select i1 %should_signext, i32 %higher_bit_after_signbit, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %higher_bit_after_signbit)
+  call void @use32(i32 %magic)
+
+  %signextended = sub i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @t2_trunc_add(i64 %data, i32 %nbits) {
+; CHECK-LABEL: @t2_trunc_add(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 64, [[NBITS:%.*]]
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP_WIDE:%.*]] = zext i32 [[LOW_BITS_TO_SKIP]] to i64
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED_WIDE:%.*]] = lshr i64 [[DATA:%.*]], [[LOW_BITS_TO_SKIP_WIDE]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = trunc i64 [[HIGH_BITS_EXTRACTED_WIDE]] to i32
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i64 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use64(i64 [[LOW_BITS_TO_SKIP_WIDE]])
+; CHECK-NEXT:    call void @use64(i64 [[HIGH_BITS_EXTRACTED_WIDE]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[MAGIC]], [[HIGH_BITS_EXTRACTED]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 64, %nbits
+  %low_bits_to_skip_wide = zext i32 %low_bits_to_skip to i64
+  %high_bits_extracted_wide = lshr i64 %data, %low_bits_to_skip_wide
+  %high_bits_extracted = trunc i64 %high_bits_extracted_wide to i32
+  %should_signext = icmp slt i64 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0 ; one-use
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use64(i64 %low_bits_to_skip_wide)
+  call void @use64(i64 %high_bits_extracted_wide)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+
+  %signextended = add i32 %magic, %high_bits_extracted
+  ret i32 %signextended
+}
+
+define i32 @t3_trunc_sub(i64 %data, i32 %nbits) {
+; CHECK-LABEL: @t3_trunc_sub(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 64, [[NBITS:%.*]]
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP_WIDE:%.*]] = zext i32 [[LOW_BITS_TO_SKIP]] to i64
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED_WIDE:%.*]] = lshr i64 [[DATA:%.*]], [[LOW_BITS_TO_SKIP_WIDE]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = trunc i64 [[HIGH_BITS_EXTRACTED_WIDE]] to i32
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i64 [[DATA]], 0
+; CHECK-NEXT:    [[HIGHER_BIT_AFTER_SIGNBIT:%.*]] = shl i32 1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[HIGHER_BIT_AFTER_SIGNBIT]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use64(i64 [[LOW_BITS_TO_SKIP_WIDE]])
+; CHECK-NEXT:    call void @use64(i64 [[HIGH_BITS_EXTRACTED_WIDE]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGHER_BIT_AFTER_SIGNBIT]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = sub i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 64, %nbits
+  %low_bits_to_skip_wide = zext i32 %low_bits_to_skip to i64
+  %high_bits_extracted_wide = lshr i64 %data, %low_bits_to_skip_wide
+  %high_bits_extracted = trunc i64 %high_bits_extracted_wide to i32
+  %should_signext = icmp slt i64 %data, 0
+  %higher_bit_after_signbit = shl i32 1, %nbits
+  %magic = select i1 %should_signext, i32 %higher_bit_after_signbit, i32 0 ; one-use
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use64(i64 %low_bits_to_skip_wide)
+  call void @use64(i64 %high_bits_extracted_wide)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %higher_bit_after_signbit)
+
+  %signextended = sub i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+; Commutativity
+
+define i32 @t4_commutativity0(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @t4_commutativity0(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+define i32 @t5_commutativity1(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @t5_commutativity1(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp sgt i32 [[DATA]], -1
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 0, i32 [[ALL_BITS_EXCEPT_LOW_NBITS]]
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp sgt i32 %data, -1 ; swapped
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 0, i32 %all_bits_except_low_nbits ; swapped
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+define i32 @t6_commutativity2(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @t6_commutativity2(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[MAGIC]], [[HIGH_BITS_EXTRACTED]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %magic, %high_bits_extracted ; swapped
+  ret i32 %signextended
+}
+
+; Extra uses
+
+define i32 @t7_trunc_extrause0(i64 %data, i32 %nbits) {
+; CHECK-LABEL: @t7_trunc_extrause0(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 64, [[NBITS:%.*]]
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP_WIDE:%.*]] = zext i32 [[LOW_BITS_TO_SKIP]] to i64
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED_WIDE:%.*]] = lshr i64 [[DATA:%.*]], [[LOW_BITS_TO_SKIP_WIDE]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = trunc i64 [[HIGH_BITS_EXTRACTED_WIDE]] to i32
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i64 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use64(i64 [[LOW_BITS_TO_SKIP_WIDE]])
+; CHECK-NEXT:    call void @use64(i64 [[HIGH_BITS_EXTRACTED_WIDE]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[MAGIC]], [[HIGH_BITS_EXTRACTED]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 64, %nbits
+  %low_bits_to_skip_wide = zext i32 %low_bits_to_skip to i64
+  %high_bits_extracted_wide = lshr i64 %data, %low_bits_to_skip_wide
+  %high_bits_extracted = trunc i64 %high_bits_extracted_wide to i32 ; has extra use
+  %should_signext = icmp slt i64 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0 ; one-use
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use64(i64 %low_bits_to_skip_wide)
+  call void @use64(i64 %high_bits_extracted_wide)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+
+  %signextended = add i32 %magic, %high_bits_extracted
+  ret i32 %signextended
+}
+define i32 @t8_trunc_extrause1(i64 %data, i32 %nbits) {
+; CHECK-LABEL: @t8_trunc_extrause1(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 64, [[NBITS:%.*]]
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP_WIDE:%.*]] = zext i32 [[LOW_BITS_TO_SKIP]] to i64
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED_WIDE:%.*]] = lshr i64 [[DATA:%.*]], [[LOW_BITS_TO_SKIP_WIDE]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = trunc i64 [[HIGH_BITS_EXTRACTED_WIDE]] to i32
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i64 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use64(i64 [[LOW_BITS_TO_SKIP_WIDE]])
+; CHECK-NEXT:    call void @use64(i64 [[HIGH_BITS_EXTRACTED_WIDE]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[MAGIC]], [[HIGH_BITS_EXTRACTED]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 64, %nbits
+  %low_bits_to_skip_wide = zext i32 %low_bits_to_skip to i64
+  %high_bits_extracted_wide = lshr i64 %data, %low_bits_to_skip_wide
+  %high_bits_extracted = trunc i64 %high_bits_extracted_wide to i32 ; one-use
+  %should_signext = icmp slt i64 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0 ; has extra use
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use64(i64 %low_bits_to_skip_wide)
+  call void @use64(i64 %high_bits_extracted_wide)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %magic, %high_bits_extracted
+  ret i32 %signextended
+}
+define i32 @n9_trunc_extrause2(i64 %data, i32 %nbits) {
+; CHECK-LABEL: @n9_trunc_extrause2(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 64, [[NBITS:%.*]]
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP_WIDE:%.*]] = zext i32 [[LOW_BITS_TO_SKIP]] to i64
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED_WIDE:%.*]] = lshr i64 [[DATA:%.*]], [[LOW_BITS_TO_SKIP_WIDE]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = trunc i64 [[HIGH_BITS_EXTRACTED_WIDE]] to i32
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i64 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use64(i64 [[LOW_BITS_TO_SKIP_WIDE]])
+; CHECK-NEXT:    call void @use64(i64 [[HIGH_BITS_EXTRACTED_WIDE]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[MAGIC]], [[HIGH_BITS_EXTRACTED]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 64, %nbits
+  %low_bits_to_skip_wide = zext i32 %low_bits_to_skip to i64
+  %high_bits_extracted_wide = lshr i64 %data, %low_bits_to_skip_wide
+  %high_bits_extracted = trunc i64 %high_bits_extracted_wide to i32 ; has extra use
+  %should_signext = icmp slt i64 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0 ; has extra use
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use64(i64 %low_bits_to_skip_wide)
+  call void @use64(i64 %high_bits_extracted_wide)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %magic, %high_bits_extracted
+  ret i32 %signextended
+}
+
+define i32 @t10_preserve_exact(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @t10_preserve_exact(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr exact i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr exact i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @t11_different_zext_of_shamt(i32 %data, i8 %nbits) {
+; CHECK-LABEL: @t11_different_zext_of_shamt(
+; CHECK-NEXT:    [[NBITS_16BIT:%.*]] = zext i8 [[NBITS:%.*]] to i16
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub nsw i16 32, [[NBITS_16BIT]]
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP_32:%.*]] = zext i16 [[LOW_BITS_TO_SKIP]] to i32
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP_32]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[NBITS_32BIT:%.*]] = zext i8 [[NBITS]] to i32
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS_32BIT]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use16(i16 [[NBITS_16BIT]])
+; CHECK-NEXT:    call void @use16(i16 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP_32]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[NBITS_32BIT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %nbits_16bit = zext i8 %nbits to i16
+  %low_bits_to_skip = sub i16 32, %nbits_16bit
+  %low_bits_to_skip_32 = zext i16 %low_bits_to_skip to i32
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip_32
+  %should_signext = icmp slt i32 %data, 0
+  %nbits_32bit = zext i8 %nbits to i32
+  %all_bits_except_low_nbits = shl i32 -1, %nbits_32bit
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use16(i16 %nbits_16bit)
+  call void @use16(i16 %low_bits_to_skip)
+  call void @use32(i32 %low_bits_to_skip_32)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %nbits_32bit)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @t12_add_sext_of_magic(i32 %data, i8 %nbits) {
+; CHECK-LABEL: @t12_add_sext_of_magic(
+; CHECK-NEXT:    [[NBITS_32BIT:%.*]] = zext i8 [[NBITS:%.*]] to i32
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub nsw i32 32, [[NBITS_32BIT]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[NBITS_16BIT:%.*]] = zext i8 [[NBITS]] to i16
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i16 -1, [[NBITS_16BIT]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i16 [[ALL_BITS_EXCEPT_LOW_NBITS]], i16 0
+; CHECK-NEXT:    [[MAGIC_WIDE:%.*]] = sext i16 [[MAGIC]] to i32
+; CHECK-NEXT:    call void @use32(i32 [[NBITS_32BIT]])
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use16(i16 [[NBITS_16BIT]])
+; CHECK-NEXT:    call void @use16(i16 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use16(i16 [[MAGIC]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC_WIDE]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC_WIDE]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %nbits_32bit = zext i8 %nbits to i32
+  %low_bits_to_skip = sub i32 32, %nbits_32bit
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %nbits_16bit = zext i8 %nbits to i16
+  %all_bits_except_low_nbits = shl i16 -1, %nbits_16bit
+  %magic = select i1 %should_signext, i16 %all_bits_except_low_nbits, i16 0
+  %magic_wide = sext i16 %magic to i32
+
+  call void @use32(i32 %nbits_32bit)
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use16(i16 %nbits_16bit)
+  call void @use16(i16 %all_bits_except_low_nbits)
+  call void @use16(i16 %magic)
+  call void @use32(i32 %magic_wide)
+
+  %signextended = add i32 %high_bits_extracted, %magic_wide
+  ret i32 %signextended
+}
+
+define i32 @t13_sub_zext_of_magic(i32 %data, i8 %nbits) {
+; CHECK-LABEL: @t13_sub_zext_of_magic(
+; CHECK-NEXT:    [[NBITS_32BIT:%.*]] = zext i8 [[NBITS:%.*]] to i32
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub nsw i32 32, [[NBITS_32BIT]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[NBITS_16BIT:%.*]] = zext i8 [[NBITS]] to i16
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i16 1, [[NBITS_16BIT]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i16 [[ALL_BITS_EXCEPT_LOW_NBITS]], i16 0
+; CHECK-NEXT:    [[MAGIC_WIDE:%.*]] = zext i16 [[MAGIC]] to i32
+; CHECK-NEXT:    call void @use32(i32 [[NBITS_32BIT]])
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use16(i16 [[NBITS_16BIT]])
+; CHECK-NEXT:    call void @use16(i16 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use16(i16 [[MAGIC]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC_WIDE]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = sub i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC_WIDE]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %nbits_32bit = zext i8 %nbits to i32
+  %low_bits_to_skip = sub i32 32, %nbits_32bit
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %nbits_16bit = zext i8 %nbits to i16
+  %all_bits_except_low_nbits = shl i16 1, %nbits_16bit
+  %magic = select i1 %should_signext, i16 %all_bits_except_low_nbits, i16 0
+  %magic_wide = zext i16 %magic to i32
+
+  call void @use32(i32 %nbits_32bit)
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use16(i16 %nbits_16bit)
+  call void @use16(i16 %all_bits_except_low_nbits)
+  call void @use16(i16 %magic)
+  call void @use32(i32 %magic_wide)
+
+  %signextended = sub i32 %high_bits_extracted, %magic_wide
+  ret i32 %signextended
+}
+
+define i32 @t14_add_sext_of_shl(i32 %data, i8 %nbits) {
+; CHECK-LABEL: @t14_add_sext_of_shl(
+; CHECK-NEXT:    [[NBITS_32BIT:%.*]] = zext i8 [[NBITS:%.*]] to i32
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub nsw i32 32, [[NBITS_32BIT]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[NBITS_16BIT:%.*]] = zext i8 [[NBITS]] to i16
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i16 -1, [[NBITS_16BIT]]
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS_WIDE:%.*]] = sext i16 [[ALL_BITS_EXCEPT_LOW_NBITS]] to i32
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS_WIDE]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[NBITS_32BIT]])
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use16(i16 [[NBITS_16BIT]])
+; CHECK-NEXT:    call void @use16(i16 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS_WIDE]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %nbits_32bit = zext i8 %nbits to i32
+  %low_bits_to_skip = sub i32 32, %nbits_32bit
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %nbits_16bit = zext i8 %nbits to i16
+  %all_bits_except_low_nbits = shl i16 -1, %nbits_16bit
+  %all_bits_except_low_nbits_wide = sext i16 %all_bits_except_low_nbits to i32
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits_wide, i32 0
+
+  call void @use32(i32 %nbits_32bit)
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use16(i16 %nbits_16bit)
+  call void @use16(i16 %all_bits_except_low_nbits)
+  call void @use32(i32 %all_bits_except_low_nbits_wide)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @t15_sub_zext_of_shl(i32 %data, i8 %nbits) {
+; CHECK-LABEL: @t15_sub_zext_of_shl(
+; CHECK-NEXT:    [[NBITS_32BIT:%.*]] = zext i8 [[NBITS:%.*]] to i32
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub nsw i32 32, [[NBITS_32BIT]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[NBITS_16BIT:%.*]] = zext i8 [[NBITS]] to i16
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i16 1, [[NBITS_16BIT]]
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS_WIDE:%.*]] = zext i16 [[ALL_BITS_EXCEPT_LOW_NBITS]] to i32
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS_WIDE]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[NBITS_32BIT]])
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use16(i16 [[NBITS_16BIT]])
+; CHECK-NEXT:    call void @use16(i16 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS_WIDE]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = sub i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %nbits_32bit = zext i8 %nbits to i32
+  %low_bits_to_skip = sub i32 32, %nbits_32bit
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %nbits_16bit = zext i8 %nbits to i16
+  %all_bits_except_low_nbits = shl i16 1, %nbits_16bit
+  %all_bits_except_low_nbits_wide = zext i16 %all_bits_except_low_nbits to i32
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits_wide, i32 0
+
+  call void @use32(i32 %nbits_32bit)
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use16(i16 %nbits_16bit)
+  call void @use16(i16 %all_bits_except_low_nbits)
+  call void @use32(i32 %all_bits_except_low_nbits_wide)
+  call void @use32(i32 %magic)
+
+  %signextended = sub i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+; Negative tests.
+
+define i32 @n16(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @n16(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 31, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 31, %nbits ; not 32
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @n17_add(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @n17_add(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 1, %nbits ; not -1
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @n18(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @n18(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 0, i32 [[ALL_BITS_EXCEPT_LOW_NBITS]]
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 0, i32 %all_bits_except_low_nbits ; wrong order
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @n19(i32 %data1, i32 %data2, i32 %nbits) {
+; CHECK-LABEL: @n19(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA1:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA2:%.*]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data1, %low_bits_to_skip ; not %data2
+  %should_signext = icmp slt i32 %data2, 0 ; not %data1
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @n20(i32 %data, i32 %nbits1, i32 %nbits2) {
+; CHECK-LABEL: @n20(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS1:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS2:%.*]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits1 ; not %nbits2
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits2 ; not %nbits1
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @n21(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @n21(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp sgt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp sgt i32 %data, 0 ; this isn't a sign bit test
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @n22(i64 %data, i32 %nbits) {
+; CHECK-LABEL: @n22(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 63, [[NBITS:%.*]]
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP_WIDE:%.*]] = zext i32 [[LOW_BITS_TO_SKIP]] to i64
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED_WIDE:%.*]] = lshr i64 [[DATA:%.*]], [[LOW_BITS_TO_SKIP_WIDE]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = trunc i64 [[HIGH_BITS_EXTRACTED_WIDE]] to i32
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i64 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use64(i64 [[LOW_BITS_TO_SKIP_WIDE]])
+; CHECK-NEXT:    call void @use64(i64 [[HIGH_BITS_EXTRACTED_WIDE]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[MAGIC]], [[HIGH_BITS_EXTRACTED]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 63, %nbits ; not 64
+  %low_bits_to_skip_wide = zext i32 %low_bits_to_skip to i64
+  %high_bits_extracted_wide = lshr i64 %data, %low_bits_to_skip_wide
+  %high_bits_extracted = trunc i64 %high_bits_extracted_wide to i32
+  %should_signext = icmp slt i64 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use64(i64 %low_bits_to_skip_wide)
+  call void @use64(i64 %high_bits_extracted_wide)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %magic, %high_bits_extracted
+  ret i32 %signextended
+}
+
+define i32 @n23(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @n23(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = ashr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = ashr i32 %data, %low_bits_to_skip ; not `lshr`
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @n24(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @n24(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[HIGHER_BIT_AFTER_SIGNBIT:%.*]] = shl i32 1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[HIGHER_BIT_AFTER_SIGNBIT]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGHER_BIT_AFTER_SIGNBIT]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = sub i32 [[MAGIC]], [[HIGH_BITS_EXTRACTED]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %higher_bit_after_signbit = shl i32 1, %nbits
+  %magic = select i1 %should_signext, i32 %higher_bit_after_signbit, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %higher_bit_after_signbit)
+  call void @use32(i32 %magic)
+
+  %signextended = sub i32 %magic, %high_bits_extracted ; wrong order; `sub` is not commutative
+  ret i32 %signextended
+}
+
+define i32 @n25_sub(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @n25_sub(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[HIGHER_BIT_AFTER_SIGNBIT:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[HIGHER_BIT_AFTER_SIGNBIT]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGHER_BIT_AFTER_SIGNBIT]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = sub i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %higher_bit_after_signbit = shl i32 -1, %nbits ; not 1
+  %magic = select i1 %should_signext, i32 %higher_bit_after_signbit, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %higher_bit_after_signbit)
+  call void @use32(i32 %magic)
+
+  %signextended = sub i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @n26(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @n26(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 -1
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 -1 ; not 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = add i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
+define i32 @n27_add_zext_of_magic(i32 %data, i8 %nbits) {
+; CHECK-LABEL: @n27_add_zext_of_magic(
+; CHECK-NEXT:    [[NBITS_32BIT:%.*]] = zext i8 [[NBITS:%.*]] to i32
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub nsw i32 32, [[NBITS_32BIT]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[NBITS_16BIT:%.*]] = zext i8 [[NBITS]] to i16
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i16 -1, [[NBITS_16BIT]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i16 [[ALL_BITS_EXCEPT_LOW_NBITS]], i16 0
+; CHECK-NEXT:    [[MAGIC_WIDE:%.*]] = zext i16 [[MAGIC]] to i32
+; CHECK-NEXT:    call void @use32(i32 [[NBITS_32BIT]])
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use16(i16 [[NBITS_16BIT]])
+; CHECK-NEXT:    call void @use16(i16 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use16(i16 [[MAGIC]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC_WIDE]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = add i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC_WIDE]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %nbits_32bit = zext i8 %nbits to i32
+  %low_bits_to_skip = sub i32 32, %nbits_32bit
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %nbits_16bit = zext i8 %nbits to i16
+  %all_bits_except_low_nbits = shl i16 -1, %nbits_16bit
+  %magic = select i1 %should_signext, i16 %all_bits_except_low_nbits, i16 0
+  %magic_wide = zext i16 %magic to i32 ; not sext
+
+  call void @use32(i32 %nbits_32bit)
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use16(i16 %nbits_16bit)
+  call void @use16(i16 %all_bits_except_low_nbits)
+  call void @use16(i16 %magic)
+  call void @use32(i32 %magic_wide)
+
+  %signextended = add i32 %high_bits_extracted, %magic_wide
+  ret i32 %signextended
+}
+
+define i32 @n28_sub_sext_of_magic(i32 %data, i8 %nbits) {
+; CHECK-LABEL: @n28_sub_sext_of_magic(
+; CHECK-NEXT:    [[NBITS_32BIT:%.*]] = zext i8 [[NBITS:%.*]] to i32
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub nsw i32 32, [[NBITS_32BIT]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[NBITS_16BIT:%.*]] = zext i8 [[NBITS]] to i16
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i16 1, [[NBITS_16BIT]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i16 [[ALL_BITS_EXCEPT_LOW_NBITS]], i16 0
+; CHECK-NEXT:    [[MAGIC_WIDE:%.*]] = sext i16 [[MAGIC]] to i32
+; CHECK-NEXT:    call void @use32(i32 [[NBITS_32BIT]])
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use16(i16 [[NBITS_16BIT]])
+; CHECK-NEXT:    call void @use16(i16 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use16(i16 [[MAGIC]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC_WIDE]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = sub i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC_WIDE]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %nbits_32bit = zext i8 %nbits to i32
+  %low_bits_to_skip = sub i32 32, %nbits_32bit
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %nbits_16bit = zext i8 %nbits to i16
+  %all_bits_except_low_nbits = shl i16 1, %nbits_16bit
+  %magic = select i1 %should_signext, i16 %all_bits_except_low_nbits, i16 0
+  %magic_wide = sext i16 %magic to i32 ; not zext
+
+  call void @use32(i32 %nbits_32bit)
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use16(i16 %nbits_16bit)
+  call void @use16(i16 %all_bits_except_low_nbits)
+  call void @use16(i16 %magic)
+  call void @use32(i32 %magic_wide)
+
+  %signextended = sub i32 %high_bits_extracted, %magic_wide
+  ret i32 %signextended
+}