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

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 afae6d97fa
commit 9ebeac6788
2 changed files with 7 additions and 5 deletions
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9
llvm/lib/IR/ConstantRange.cpp
View File

@ -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
llvm/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