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[InstCombine] allow X + signbit --> X ^ signbit for vector splats

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275691 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjay Patel 2016-07-16 18:29:26 +00:00
parent 713ceaf392
commit 2e9433d42d
2 changed files with 11 additions and 4 deletions
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13
lib/Transforms/InstCombine/InstCombineAddSub.cpp
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@ -1042,12 +1042,16 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
if (Value *V = SimplifyUsingDistributiveLaws(I))
return replaceInstUsesWith(I, V);
if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
const APInt *Val;
if (match(RHS, m_APInt(Val))) {
// X + (signbit) --> X ^ signbit
const APInt &Val = CI->getValue();
if (Val.isSignBit())
if (Val->isSignBit())
return BinaryOperator::CreateXor(LHS, RHS);
}
// FIXME: Use the match above instead of dyn_cast to allow these transforms
// for splat vectors.
if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
// See if SimplifyDemandedBits can simplify this. This handles stuff like
// (X & 254)+1 -> (X&254)|1
if (SimplifyDemandedInstructionBits(I))
@ -1149,6 +1153,9 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
return BinaryOperator::CreateSub(SubOne(CRHS), X);
}
// FIXME: We already did a check for ConstantInt RHS above this.
// FIXME: Is this pattern covered by another fold? No regression tests fail on
// removal.
if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
// (X & FF00) + xx00 -> (X+xx00) & FF00
Value *X;

2
test/Transforms/InstCombine/apint-add.ll
View File

@ -36,7 +36,7 @@ define i15 @test3(i15 %x) {
; X + signbit --> X ^ signbit
define <2 x i5> @test3vec(<2 x i5> %x) {
; CHECK-LABEL: @test3vec(
; CHECK-NEXT: [[Y:%.*]] = add <2 x i5> %x, <i5 -16, i5 -16>
; CHECK-NEXT: [[Y:%.*]] = xor <2 x i5> %x, <i5 -16, i5 -16>
; CHECK-NEXT: ret <2 x i5> [[Y]]
;
%y = add <2 x i5> %x, <i5 16, i5 16>