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[ConstantRange][CVP] Make use of abs poison flag

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Pass the abs poison flag to the underlying ConstantRange
implementation, allowing CVP to simplify based on it.

Importantly, this recognizes that abs with poison flag is actually
non-negative...
This commit is contained in:
Nikita Popov 2020-07-30 22:54:53 +02:00
parent 50a1ea2ba8
commit 3f67e02a40
2 changed files with 7 additions and 5 deletions
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9
lib/IR/ConstantRange.cpp
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@ -872,9 +872,12 @@ ConstantRange ConstantRange::intrinsic(Intrinsic::ID IntrinsicID,
return Ops[0].smin(Ops[1]);
case Intrinsic::smax:
return Ops[0].smax(Ops[1]);
case Intrinsic::abs:
// TODO: Make use of poison flag.
return Ops[0].abs();
case Intrinsic::abs: {
const APInt *IntMinIsPoison = Ops[1].getSingleElement();
assert(IntMinIsPoison && "Must be known (immarg)");
assert(IntMinIsPoison->getBitWidth() == 1 && "Must be boolean");
return Ops[0].abs(IntMinIsPoison->getBoolValue());
}
default:
assert(!isIntrinsicSupported(IntrinsicID) && "Shouldn't be supported");
llvm_unreachable("Unsupported intrinsic");

3
test/Transforms/CorrelatedValuePropagation/minmaxabs.ll
View File

@ -141,8 +141,7 @@ define void @test_abs3(i32 %x) {
; CHECK-NEXT: [[A:%.*]] = call i32 @llvm.abs.i32(i32 [[X:%.*]], i1 true)
; CHECK-NEXT: br label [[SPLIT:%.*]]
; CHECK: split:
; CHECK-NEXT: [[C1:%.*]] = icmp sge i32 [[A]], 0
; CHECK-NEXT: call void @use(i1 [[C1]])
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[C2:%.*]] = icmp sgt i32 [[A]], 0
; CHECK-NEXT: call void @use(i1 [[C2]])
; CHECK-NEXT: ret void