diff options
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 18 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/xor.ll | 17 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/zext.ll | 2 |
3 files changed, 5 insertions, 32 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 10faf478676..2f6e411345f 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -277,20 +277,10 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, return InsertNewInstWith(And, *I); } - // If the RHS is a constant, see if we can change it. Don't alter a -1 - // constant because that's a canonical 'not' op, and that is better for - // combining, SCEV, and codegen. - const APInt *C; - if (match(I->getOperand(1), m_APInt(C)) && !C->isAllOnesValue()) { - if (DemandedMask.isSubsetOf(*C)) { - // Force bits to 1 to create a 'not' op. - I->setOperand(1, ConstantInt::getAllOnesValue(VTy)); - return I; - } - // If we can't turn this into a 'not', try to shrink the constant. - if (ShrinkDemandedConstant(I, 1, DemandedMask)) - return I; - } + // If the RHS is a constant, see if we can simplify it. + // FIXME: for XOR, we prefer to force bits to 1 if they will make a -1. + if (ShrinkDemandedConstant(I, 1, DemandedMask)) + return I; // If our LHS is an 'and' and if it has one use, and if any of the bits we // are flipping are known to be set, then the xor is just resetting those diff --git a/llvm/test/Transforms/InstCombine/xor.ll b/llvm/test/Transforms/InstCombine/xor.ll index 33fe557ae5a..570155b1623 100644 --- a/llvm/test/Transforms/InstCombine/xor.ll +++ b/llvm/test/Transforms/InstCombine/xor.ll @@ -536,20 +536,3 @@ define i32 @test38(i32 %A, i32 %B) { %xor = xor i32 %and, %B ret i32 %xor } - -; PR32706 - https://bugs.llvm.org/show_bug.cgi?id=32706 -; Pin an xor constant operand to -1 if possible because 'not' is better for SCEV and codegen. - -define i32 @not_is_canonical(i32 %x, i32 %y) { -; CHECK-LABEL: @not_is_canonical( -; CHECK-NEXT: [[SUB:%.*]] = xor i32 %x, -1 -; CHECK-NEXT: [[ADD:%.*]] = add i32 [[SUB]], %y -; CHECK-NEXT: [[MUL:%.*]] = shl i32 [[ADD]], 2 -; CHECK-NEXT: ret i32 [[MUL]] -; - %sub = xor i32 %x, 1073741823 - %add = add i32 %sub, %y - %mul = shl i32 %add, 2 - ret i32 %mul -} - diff --git a/llvm/test/Transforms/InstCombine/zext.ll b/llvm/test/Transforms/InstCombine/zext.ll index d5c52bd811b..887d839cb8c 100644 --- a/llvm/test/Transforms/InstCombine/zext.ll +++ b/llvm/test/Transforms/InstCombine/zext.ll @@ -35,7 +35,7 @@ define <2 x i64> @test3(<2 x i64> %A) { define <2 x i64> @test4(<2 x i64> %A) { ; CHECK-LABEL: @test4( -; CHECK-NEXT: [[TMP1:%.*]] = xor <2 x i64> %A, <i64 -1, i64 -1> +; CHECK-NEXT: [[TMP1:%.*]] = xor <2 x i64> %A, <i64 63, i64 63> ; CHECK-NEXT: [[XOR:%.*]] = and <2 x i64> [[TMP1]], <i64 23, i64 42> ; CHECK-NEXT: ret <2 x i64> [[XOR]] ; |
