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[InstCombine] add tests to show potential missing folds; NFC 

As noted in https://bugs.llvm.org/show_bug.cgi?id=33138 and
the comments, there are multiple ways to view this. If we
choose not to solve this in InstCombine, these tests will
serve as documentation of that choice.

llvm-svn: 303755
This commit is contained in:
Sanjay Patel 2017-05-24 14:56:51 +00:00
parent 8973a0a22c
commit 6232406b34
1 changed files with 39 additions and 0 deletions
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39
llvm/test/Transforms/InstCombine/icmp-xor-signbit.ll
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@ -187,3 +187,42 @@ define <2 x i1> @uge_to_slt_splat(<2 x i8> %x) {
ret <2 x i1> %cmp
}
; PR33138, part 2: https://bugs.llvm.org/show_bug.cgi?id=33138
; TODO: We could look through vector bitcasts for icmp folds,
; or we could canonicalize bitcast ahead of logic ops with constants.
define <8 x i1> @sgt_to_ugt_bitcasted_splat(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @sgt_to_ugt_bitcasted_splat(
; CHECK-NEXT: [[A:%.*]] = xor <2 x i32> %x, <i32 -2139062144, i32 -2139062144>
; CHECK-NEXT: [[B:%.*]] = xor <2 x i32> %y, <i32 -2139062144, i32 -2139062144>
; CHECK-NEXT: [[C:%.*]] = bitcast <2 x i32> [[A]] to <8 x i8>
; CHECK-NEXT: [[D:%.*]] = bitcast <2 x i32> [[B]] to <8 x i8>
; CHECK-NEXT: [[E:%.*]] = icmp sgt <8 x i8> [[C]], [[D]]
; CHECK-NEXT: ret <8 x i1> [[E]]
;
%a = xor <2 x i32> %x, <i32 2155905152, i32 2155905152> ; 0x80808080
%b = xor <2 x i32> %y, <i32 2155905152, i32 2155905152>
%c = bitcast <2 x i32> %a to <8 x i8>
%d = bitcast <2 x i32> %b to <8 x i8>
%e = icmp sgt <8 x i8> %c, %d
ret <8 x i1> %e
}
; TODO: This is false (little-endian). How should that be recognized?
; Ie, should InstSimplify know this directly, should InstCombine canonicalize
; this so InstSimplify can know this, or is that not something that we want
; either pass to recognize?
define <2 x i1> @negative_simplify_splat(<4 x i8> %x) {
; CHECK-LABEL: @negative_simplify_splat(
; CHECK-NEXT: [[A:%.*]] = or <4 x i8> %x, <i8 0, i8 -128, i8 0, i8 -128>
; CHECK-NEXT: [[B:%.*]] = bitcast <4 x i8> [[A]] to <2 x i16>
; CHECK-NEXT: [[C:%.*]] = icmp sgt <2 x i16> [[B]], zeroinitializer
; CHECK-NEXT: ret <2 x i1> [[C]]
;
%a = or <4 x i8> %x, <i8 0, i8 128, i8 0, i8 128>
%b = bitcast <4 x i8> %a to <2 x i16>
%c = icmp sgt <2 x i16> %b, zeroinitializer
ret <2 x i1> %c
}