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[InstCombine] use constant pattern matchers with icmp+sext

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The previous code worked with vectors, but it failed when the
vector constants contained undef elements. 
The matchers handle those cases.

llvm-svn: 335262
This commit is contained in:
Sanjay Patel 2018-06-21 17:51:44 +00:00
parent d300aa80a3
commit 7d287b088c
2 changed files with 15 additions and 19 deletions
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23
lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -1191,22 +1191,19 @@ Instruction *InstCombiner::transformSExtICmp(ICmpInst *ICI, Instruction &CI) {
if (!Op1->getType()->isIntOrIntVectorTy())
return nullptr;
if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
if ((Pred == ICmpInst::ICMP_SLT && match(Op1, m_ZeroInt())) ||
(Pred == ICmpInst::ICMP_SGT && match(Op1, m_AllOnes()))) {
// (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if negative
// (x >s -1) ? -1 : 0 -> not (ashr x, 31) -> all ones if positive
if ((Pred == ICmpInst::ICMP_SLT && Op1C->isNullValue()) ||
(Pred == ICmpInst::ICMP_SGT && Op1C->isAllOnesValue())) {
Value *Sh = ConstantInt::get(Op0->getType(),
Op0->getType()->getScalarSizeInBits() - 1);
Value *In = Builder.CreateAShr(Op0, Sh, Op0->getName() + ".lobit");
if (In->getType() != CI.getType())
In = Builder.CreateIntCast(In, CI.getType(), true /*SExt*/);
Value *Sh = ConstantInt::get(Op0->getType(),
Op0->getType()->getScalarSizeInBits()-1);
Value *In = Builder.CreateAShr(Op0, Sh, Op0->getName() + ".lobit");
if (In->getType() != CI.getType())
In = Builder.CreateIntCast(In, CI.getType(), true /*SExt*/);
if (Pred == ICmpInst::ICMP_SGT)
In = Builder.CreateNot(In, In->getName() + ".not");
return replaceInstUsesWith(CI, In);
}
if (Pred == ICmpInst::ICMP_SGT)
In = Builder.CreateNot(In, In->getName() + ".not");
return replaceInstUsesWith(CI, In);
}
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {

11
test/Transforms/InstCombine/vec_sext.ll
View File

@ -47,9 +47,8 @@ define <4 x i32> @test1(<4 x i32> %a, <4 x i32> %b) {
define <2 x i32> @is_negative_undef_elt(<2 x i32> %a) {
; CHECK-LABEL: @is_negative_undef_elt(
; CHECK-NEXT: [[CMP:%.*]] = icmp slt <2 x i32> [[A:%.*]], <i32 0, i32 undef>
; CHECK-NEXT: [[SEXT:%.*]] = sext <2 x i1> [[CMP]] to <2 x i32>
; CHECK-NEXT: ret <2 x i32> [[SEXT]]
; CHECK-NEXT: [[A_LOBIT:%.*]] = ashr <2 x i32> [[A:%.*]], <i32 31, i32 31>
; CHECK-NEXT: ret <2 x i32> [[A_LOBIT]]
;
%cmp = icmp slt <2 x i32> %a, <i32 0, i32 undef>
%sext = sext <2 x i1> %cmp to <2 x i32>
@ -59,9 +58,9 @@ define <2 x i32> @is_negative_undef_elt(<2 x i32> %a) {
define <2 x i32> @is_positive_undef_elt(<2 x i32> %a) {
; CHECK-LABEL: @is_positive_undef_elt(
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i32> [[A:%.*]], <i32 undef, i32 -1>
; CHECK-NEXT: [[SEXT:%.*]] = sext <2 x i1> [[CMP]] to <2 x i32>
; CHECK-NEXT: ret <2 x i32> [[SEXT]]
; CHECK-NEXT: [[A_LOBIT:%.*]] = ashr <2 x i32> [[A:%.*]], <i32 31, i32 31>
; CHECK-NEXT: [[A_LOBIT_NOT:%.*]] = xor <2 x i32> [[A_LOBIT]], <i32 -1, i32 -1>
; CHECK-NEXT: ret <2 x i32> [[A_LOBIT_NOT]]
;
%cmp = icmp sgt <2 x i32> %a, <i32 undef, i32 -1>
%sext = sext <2 x i1> %cmp to <2 x i32>