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[InstCombine] look through bswap/bitreverse for equality comparisons 

I noticed this missed bswap optimization in the CGP memcmp() expansion, 
and then I saw that we don't have the fold in InstCombine.

Differential Revision: https://reviews.llvm.org/D34763

llvm-svn: 306980
This commit is contained in:
Sanjay Patel 2017-07-02 14:34:50 +00:00
parent 91a00b974d
commit c3d5cf0bb7
2 changed files with 13 additions and 12 deletions
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9
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -3438,6 +3438,15 @@ Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
}
}
// If both operands are byte-swapped or bit-reversed, just compare the
// original values.
// TODO: Move this to a function similar to foldICmpIntrinsicWithConstant()
// and handle more intrinsics.
if ((match(Op0, m_BSwap(m_Value(A))) && match(Op1, m_BSwap(m_Value(B)))) ||
(match(Op0, m_Intrinsic<Intrinsic::bitreverse>(m_Value(A))) &&
match(Op1, m_Intrinsic<Intrinsic::bitreverse>(m_Value(B)))))
return new ICmpInst(Pred, A, B);
return nullptr;
}

16
llvm/test/Transforms/InstCombine/icmp.ll
View File

@ -2979,9 +2979,7 @@ declare i32 @llvm.bswap.i32(i32)
define i1 @bswap_ne(i32 %x, i32 %y) {
; CHECK-LABEL: @bswap_ne(
; CHECK-NEXT: [[SWAPX:%.*]] = call i32 @llvm.bswap.i32(i32 %x)
; CHECK-NEXT: [[SWAPY:%.*]] = call i32 @llvm.bswap.i32(i32 %y)
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[SWAPX]], [[SWAPY]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 %x, %y
; CHECK-NEXT: ret i1 [[CMP]]
;
%swapx = call i32 @llvm.bswap.i32(i32 %x)
@ -2994,9 +2992,7 @@ declare <8 x i16> @llvm.bswap.v8i16(<8 x i16>)
define <8 x i1> @bswap_vec_eq(<8 x i16> %x, <8 x i16> %y) {
; CHECK-LABEL: @bswap_vec_eq(
; CHECK-NEXT: [[SWAPX:%.*]] = call <8 x i16> @llvm.bswap.v8i16(<8 x i16> %x)
; CHECK-NEXT: [[SWAPY:%.*]] = call <8 x i16> @llvm.bswap.v8i16(<8 x i16> %y)
; CHECK-NEXT: [[CMP:%.*]] = icmp eq <8 x i16> [[SWAPX]], [[SWAPY]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq <8 x i16> %x, %y
; CHECK-NEXT: ret <8 x i1> [[CMP]]
;
%swapx = call <8 x i16> @llvm.bswap.v8i16(<8 x i16> %x)
@ -3009,9 +3005,7 @@ declare i64 @llvm.bitreverse.i64(i64)
define i1 @bitreverse_eq(i64 %x, i64 %y) {
; CHECK-LABEL: @bitreverse_eq(
; CHECK-NEXT: [[REVX:%.*]] = call i64 @llvm.bitreverse.i64(i64 %x)
; CHECK-NEXT: [[REVY:%.*]] = call i64 @llvm.bitreverse.i64(i64 %y)
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[REVX]], [[REVY]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 %x, %y
; CHECK-NEXT: ret i1 [[CMP]]
;
%revx = call i64 @llvm.bitreverse.i64(i64 %x)
@ -3024,9 +3018,7 @@ declare <8 x i16> @llvm.bitreverse.v8i16(<8 x i16>)
define <8 x i1> @bitreverse_vec_ne(<8 x i16> %x, <8 x i16> %y) {
; CHECK-LABEL: @bitreverse_vec_ne(
; CHECK-NEXT: [[REVX:%.*]] = call <8 x i16> @llvm.bitreverse.v8i16(<8 x i16> %x)
; CHECK-NEXT: [[REVY:%.*]] = call <8 x i16> @llvm.bitreverse.v8i16(<8 x i16> %y)
; CHECK-NEXT: [[CMP:%.*]] = icmp ne <8 x i16> [[REVX]], [[REVY]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ne <8 x i16> %x, %y
; CHECK-NEXT: ret <8 x i1> [[CMP]]
;
%revx = call <8 x i16> @llvm.bitreverse.v8i16(<8 x i16> %x)