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[InstCombine] Support ssub.sat canonicalization for non-splats

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Extend ssub.sat(X, C) -> sadd.sat(X, -C) canonicalization to also
support non-splat vector constants. This is done by generalizing
the implementation of the isNotMinSignedValue() helper to return
true for constants that are non-splat, but don't contain any
signed min elements.

Differential Revision: https://reviews.llvm.org/D55011

llvm-svn: 348072
This commit is contained in:
Nikita Popov 2018-12-01 10:58:34 +00:00
parent 2c4b0ae812
commit 146fc6e46f
3 changed files with 16 additions and 21 deletions
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19
lib/IR/Constants.cpp
View File

@ -184,18 +184,15 @@ bool Constant::isNotMinSignedValue() const {
if (const ConstantFP *CFP = dyn_cast<ConstantFP>(this))
return !CFP->getValueAPF().bitcastToAPInt().isMinSignedValue();
// Check for constant vectors which are splats of INT_MIN values.
if (const ConstantVector *CV = dyn_cast<ConstantVector>(this))
if (Constant *Splat = CV->getSplatValue())
return Splat->isNotMinSignedValue();
// Check for constant vectors which are splats of INT_MIN values.
if (const ConstantDataVector *CV = dyn_cast<ConstantDataVector>(this)) {
if (CV->isSplat()) {
if (CV->getElementType()->isFloatingPointTy())
return !CV->getElementAsAPFloat(0).bitcastToAPInt().isMinSignedValue();
return !CV->getElementAsAPInt(0).isMinSignedValue();
// Check that vectors don't contain INT_MIN
if (this->getType()->isVectorTy()) {
unsigned NumElts = this->getType()->getVectorNumElements();
for (unsigned i = 0; i != NumElts; ++i) {
Constant *Elt = this->getAggregateElement(i);
if (!Elt || !Elt->isNotMinSignedValue())
return false;
}
return true;
}
// It *may* contain INT_MIN, we can't tell.

9
lib/Transforms/InstCombine/InstCombineCalls.cpp
View File

@ -2104,11 +2104,10 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
}
// ssub.sat(X, C) -> sadd.sat(X, -C) if C != MIN
// TODO: Support non-splat C.
const APInt *C;
if (IID == Intrinsic::ssub_sat && match(Arg1, m_APInt(C)) &&
!C->isMinSignedValue()) {
Value *NegVal = ConstantInt::get(II->getType(), -*C);
Constant *C;
if (IID == Intrinsic::ssub_sat && match(Arg1, m_Constant(C)) &&
C->isNotMinSignedValue()) {
Value *NegVal = ConstantExpr::getNeg(C);
return replaceInstUsesWith(
*II, Builder.CreateBinaryIntrinsic(
Intrinsic::sadd_sat, Arg0, NegVal));

9
test/Transforms/InstCombine/saturating-add-sub.ll
View File

@ -337,11 +337,10 @@ define <2 x i8> @test_vector_ssub_canonical(<2 x i8> %a) {
ret <2 x i8> %r
}
; Canonicalization for non-splat constants is not supported yet.
define <2 x i8> @test_vector_ssub_canonical_min_non_splat(<2 x i8> %a) {
; CHECK-LABEL: @test_vector_ssub_canonical_min_non_splat(
; CHECK-NEXT: [[R:%.*]] = call <2 x i8> @llvm.ssub.sat.v2i8(<2 x i8> [[A:%.*]], <2 x i8> <i8 10, i8 -10>)
; CHECK-NEXT: ret <2 x i8> [[R]]
; CHECK-NEXT: [[TMP1:%.*]] = call <2 x i8> @llvm.sadd.sat.v2i8(<2 x i8> [[A:%.*]], <2 x i8> <i8 -10, i8 10>)
; CHECK-NEXT: ret <2 x i8> [[TMP1]]
;
%r = call <2 x i8> @llvm.ssub.sat.v2i8(<2 x i8> %a, <2 x i8> <i8 10, i8 -10>)
ret <2 x i8> %r
@ -630,8 +629,8 @@ define i8 @test_scalar_ssub_neg_nneg(i8 %a) {
define <2 x i8> @test_vector_ssub_neg_nneg(<2 x i8> %a) {
; CHECK-LABEL: @test_vector_ssub_neg_nneg(
; CHECK-NEXT: [[A_NEG:%.*]] = or <2 x i8> [[A:%.*]], <i8 -128, i8 -128>
; CHECK-NEXT: [[R:%.*]] = call <2 x i8> @llvm.ssub.sat.v2i8(<2 x i8> [[A_NEG]], <2 x i8> <i8 10, i8 20>)
; CHECK-NEXT: ret <2 x i8> [[R]]
; CHECK-NEXT: [[TMP1:%.*]] = call <2 x i8> @llvm.sadd.sat.v2i8(<2 x i8> [[A_NEG]], <2 x i8> <i8 -10, i8 -20>)
; CHECK-NEXT: ret <2 x i8> [[TMP1]]
;
%a_neg = or <2 x i8> %a, <i8 -128, i8 -128>
%r = call <2 x i8> @llvm.ssub.sat.v2i8(<2 x i8> %a_neg, <2 x i8> <i8 10, i8 20>)