[InstCombine] add tests for load narrowing; NFC

Baseline results for D64432.

llvm-svn: 366901

llvm/test/Transforms/InstCombine/trunc-load.ll

@@ -2,8 +2,10 @@
 ; RUN: opt < %s -instcombine -S -data-layout="e-n16:32:64" | FileCheck %s --check-prefixes=CHECK,LE
 ; RUN: opt < %s -instcombine -S -data-layout="E-n16:32:64" | FileCheck %s --check-prefixes=CHECK,BE
 
-define i32 @truncload(i64* %ptr) {
+; Don't narrow if it would lose information about the dereferenceable range of the pointer.
-; CHECK-LABEL: @truncload(
+
+define i32 @truncload_no_deref(i64* %ptr) {
+; CHECK-LABEL: @truncload_no_deref(
 ; CHECK-NEXT:    [[X:%.*]] = load i64, i64* [[PTR:%.*]], align 4
 ; CHECK-NEXT:    [[R:%.*]] = trunc i64 [[X]] to i32
 ; CHECK-NEXT:    ret i32 [[R]]
@@ -13,7 +15,33 @@ define i32 @truncload(i64* %ptr) {
   ret i32 %r
 }
 
-define i16 @truncload_align(i32* %ptr) {
+define i32 @truncload_small_deref(i64* dereferenceable(7) %ptr) {
+; CHECK-LABEL: @truncload_small_deref(
+; CHECK-NEXT:    [[X:%.*]] = load i64, i64* [[PTR:%.*]], align 4
+; CHECK-NEXT:    [[R:%.*]] = trunc i64 [[X]] to i32
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %x = load i64, i64* %ptr
+  %r = trunc i64 %x to i32
+  ret i32 %r
+}
+
+; On little-endian, we can narrow the load without an offset.
+
+define i32 @truncload_deref(i64* dereferenceable(8) %ptr) {
+; CHECK-LABEL: @truncload_deref(
+; CHECK-NEXT:    [[X:%.*]] = load i64, i64* [[PTR:%.*]], align 4
+; CHECK-NEXT:    [[R:%.*]] = trunc i64 [[X]] to i32
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %x = load i64, i64* %ptr
+  %r = trunc i64 %x to i32
+  ret i32 %r
+}
+
+; Preserve alignment.
+
+define i16 @truncload_align(i32* dereferenceable(14) %ptr) {
 ; CHECK-LABEL: @truncload_align(
 ; CHECK-NEXT:    [[X:%.*]] = load i32, i32* [[PTR:%.*]], align 16
 ; CHECK-NEXT:    [[R:%.*]] = trunc i32 [[X]] to i16
@@ -24,9 +52,11 @@ define i16 @truncload_align(i32* %ptr) {
   ret i16 %r
 }
 
+; Negative test - extra use means we would not eliminate the original load.
+
 declare void @use(i64)
 
-define i32 @truncload_extra_use(i64* %ptr) {
+define i32 @truncload_extra_use(i64* dereferenceable(100) %ptr) {
 ; CHECK-LABEL: @truncload_extra_use(
 ; CHECK-NEXT:    [[X:%.*]] = load i64, i64* [[PTR:%.*]], align 2
 ; CHECK-NEXT:    call void @use(i64 [[X]])
@@ -39,7 +69,9 @@ define i32 @truncload_extra_use(i64* %ptr) {
   ret i32 %r
 }
 
-define i8 @truncload_type(i64* %ptr) {
+; Negative test - don't create a load if the type is not allowed by the data-layout.
+
+define i8 @truncload_type(i64* dereferenceable(9) %ptr) {
 ; CHECK-LABEL: @truncload_type(
 ; CHECK-NEXT:    [[X:%.*]] = load i64, i64* [[PTR:%.*]], align 2
 ; CHECK-NEXT:    [[R:%.*]] = trunc i64 [[X]] to i8
@@ -50,7 +82,9 @@ define i8 @truncload_type(i64* %ptr) {
   ret i8 %r
 }
 
-define i32 @truncload_volatile(i64* %ptr) {
+; Negative test - don't transform volatiles.
+
+define i32 @truncload_volatile(i64* dereferenceable(8) %ptr) {
 ; CHECK-LABEL: @truncload_volatile(
 ; CHECK-NEXT:    [[X:%.*]] = load volatile i64, i64* [[PTR:%.*]], align 8
 ; CHECK-NEXT:    [[R:%.*]] = trunc i64 [[X]] to i32
@@ -61,7 +95,9 @@ define i32 @truncload_volatile(i64* %ptr) {
   ret i32 %r
 }
 
-define i32 @truncload_address_space(i64 addrspace(1)* %ptr) {
+; Preserve address space.
+
+define i32 @truncload_address_space(i64 addrspace(1)* dereferenceable(8) %ptr) {
 ; CHECK-LABEL: @truncload_address_space(
 ; CHECK-NEXT:    [[X:%.*]] = load i64, i64 addrspace(1)* [[PTR:%.*]], align 4
 ; CHECK-NEXT:    [[R:%.*]] = trunc i64 [[X]] to i32