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[LVI] Learn value ranges from ctpop results #121945

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Merged
merged 1 commit into from
Jan 15, 2025
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[LVI] Learn value ranges from ctpop results #121945

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24 changes: 24 additions & 0 deletions llvm/lib/Analysis/LazyValueInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1159,6 +1159,27 @@ getRangeViaSLT(CmpInst::Predicate Pred, APInt RHS,
return std::nullopt;
}

/// Get value range for a "ctpop(Val) Pred RHS" condition.
static ValueLatticeElement getValueFromICmpCtpop(ICmpInst::Predicate Pred,
Value *RHS) {
unsigned BitWidth = RHS->getType()->getScalarSizeInBits();

auto *RHSConst = dyn_cast<ConstantInt>(RHS);
if (!RHSConst)
return ValueLatticeElement::getOverdefined();

ConstantRange ResValRange =
ConstantRange::makeExactICmpRegion(Pred, RHSConst->getValue());

unsigned ResMin = ResValRange.getUnsignedMin().getLimitedValue(BitWidth);
unsigned ResMax = ResValRange.getUnsignedMax().getLimitedValue(BitWidth);

APInt ValMin = APInt::getLowBitsSet(BitWidth, ResMin);
APInt ValMax = APInt::getHighBitsSet(BitWidth, ResMax);
return ValueLatticeElement::getRange(
ConstantRange::getNonEmpty(std::move(ValMin), ValMax + 1));
}

std::optional<ValueLatticeElement> LazyValueInfoImpl::getValueFromICmpCondition(
Value *Val, ICmpInst *ICI, bool isTrueDest, bool UseBlockValue) {
Value *LHS = ICI->getOperand(0);
Expand Down Expand Up @@ -1192,6 +1213,9 @@ std::optional<ValueLatticeElement> LazyValueInfoImpl::getValueFromICmpCondition(
return getValueFromSimpleICmpCondition(SwappedPred, LHS, Offset, ICI,
UseBlockValue);

if (match(LHS, m_Intrinsic<Intrinsic::ctpop>(m_Specific(Val))))
return getValueFromICmpCtpop(EdgePred, RHS);

const APInt *Mask, *C;
if (match(LHS, m_And(m_Specific(Val), m_APInt(Mask))) &&
match(RHS, m_APInt(C))) {
Expand Down
142 changes: 142 additions & 0 deletions llvm/test/Transforms/CorrelatedValuePropagation/ctpop-range.ll
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@@ -0,0 +1,142 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -S -passes=correlated-propagation %s | FileCheck %s

declare void @use(i1)

define void @ctpop1(i8 %v) {
; CHECK-LABEL: define void @ctpop1(
; CHECK-SAME: i8 [[V:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[RES:%.*]] = call range(i8 0, 9) i8 @llvm.ctpop.i8(i8 [[V]])
; CHECK-NEXT: [[C0_0:%.*]] = icmp samesign uge i8 [[RES]], 3
; CHECK-NEXT: [[C0_1:%.*]] = icmp samesign ule i8 [[RES]], 7
; CHECK-NEXT: [[C0:%.*]] = and i1 [[C0_0]], [[C0_1]]
; CHECK-NEXT: br i1 [[C0]], label %[[RANGE_3_8:.*]], label %[[ED:.*]]
; CHECK: [[RANGE_3_8]]:
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[CMP1:%.*]] = icmp uge i8 [[V]], 8
; CHECK-NEXT: call void @use(i1 [[CMP1]])
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[CMP3:%.*]] = icmp ule i8 [[V]], -3
; CHECK-NEXT: call void @use(i1 [[CMP3]])
; CHECK-NEXT: ret void
; CHECK: [[ED]]:
; CHECK-NEXT: ret void
;
entry:
%res = call range(i8 0, 9) i8 @llvm.ctpop.i8(i8 %v)
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Suggested change
%res = call range(i8 0, 9) i8 @llvm.ctpop.i8(i8 %v)
%res = call i8 @llvm.ctpop.i8(i8 %v)

I don't think these range annotations are really relevant to the test?

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Removed.

%c0.0 = icmp uge i8 %res, 3
%c0.1 = icmp ule i8 %res, 7
%c0 = and i1 %c0.0, %c0.1
br i1 %c0, label %range.3.8, label %ed

range.3.8:
%cmp0 = icmp uge i8 %v, 7
call void @use(i1 %cmp0) ; true
%cmp1 = icmp uge i8 %v, 8
call void @use(i1 %cmp1) ; unknown
%cmp2 = icmp ule i8 %v, 254
call void @use(i1 %cmp2) ; true
%cmp3 = icmp ule i8 %v, 253
call void @use(i1 %cmp3) ; unknown
ret void

ed:
ret void
}

define void @ctpop2(i8 %v) {
; CHECK-LABEL: define void @ctpop2(
; CHECK-SAME: i8 [[V:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[RES:%.*]] = call range(i8 0, 9) i8 @llvm.ctpop.i8(i8 [[V]])
; CHECK-NEXT: [[C2_0:%.*]] = icmp samesign uge i8 [[RES]], 1
; CHECK-NEXT: [[C2_1:%.*]] = icmp samesign ule i8 [[RES]], 4
; CHECK-NEXT: [[C2:%.*]] = and i1 [[C2_0]], [[C2_1]]
; CHECK-NEXT: br i1 [[C2]], label %[[RANGE_1_5:.*]], label %[[ED:.*]]
; CHECK: [[RANGE_1_5]]:
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[CMP9:%.*]] = icmp uge i8 [[V]], 2
; CHECK-NEXT: call void @use(i1 [[CMP9]])
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[CMP11:%.*]] = icmp ule i8 [[V]], -17
; CHECK-NEXT: call void @use(i1 [[CMP11]])
; CHECK-NEXT: ret void
; CHECK: [[ED]]:
; CHECK-NEXT: ret void
;
entry:
%res = call range(i8 0, 9) i8 @llvm.ctpop.i8(i8 %v)
%c2.0 = icmp uge i8 %res, 1
%c2.1 = icmp ule i8 %res, 4
%c2 = and i1 %c2.0, %c2.1
br i1 %c2, label %range.1.5, label %ed

range.1.5:
%cmp8 = icmp uge i8 %v, 1
call void @use(i1 %cmp8) ; true
%cmp9 = icmp uge i8 %v, 2
call void @use(i1 %cmp9) ; unknown
%cmp10 = icmp ule i8 %v, 240
call void @use(i1 %cmp10) ; true
%cmp11 = icmp ule i8 %v, 239
call void @use(i1 %cmp11) ; unknown
ret void

ed:
ret void
}

define void @ctpop3(i8 %v) {
; CHECK-LABEL: define void @ctpop3(
; CHECK-SAME: i8 [[V:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[RES:%.*]] = call i8 @llvm.ctpop.i8(i8 [[V]])
; CHECK-NEXT: [[C3:%.*]] = icmp samesign uge i8 [[RES]], 8
; CHECK-NEXT: br i1 [[C3]], label %[[RANGE_8_9:.*]], label %[[ED:.*]]
; CHECK: [[RANGE_8_9]]:
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: ret void
; CHECK: [[ED]]:
; CHECK-NEXT: ret void
;
entry:
%res = call i8 @llvm.ctpop.i8(i8 %v)
%c3 = icmp uge i8 %res, 8
br i1 %c3, label %range.8.9, label %ed

range.8.9:
%cmp4 = icmp eq i8 %v, -1
call void @use(i1 %cmp4) ; true
ret void

ed:
ret void
}

define void @ctpop4(i8 %v) {
; CHECK-LABEL: define void @ctpop4(
; CHECK-SAME: i8 [[V:%.*]]) {
; CHECK-NEXT: [[TEST4:.*:]]
; CHECK-NEXT: [[RES:%.*]] = call i8 @llvm.ctpop.i8(i8 [[V]])
; CHECK-NEXT: [[C4:%.*]] = icmp eq i8 [[RES]], 0
; CHECK-NEXT: br i1 [[C4]], label %[[RANGE_0_1:.*]], label %[[ED:.*]]
; CHECK: [[RANGE_0_1]]:
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: ret void
; CHECK: [[ED]]:
; CHECK-NEXT: ret void
;
test4:
%res = call i8 @llvm.ctpop.i8(i8 %v)
%c4 = icmp eq i8 %res, 0
br i1 %c4, label %range.0.1, label %ed

range.0.1:
%cmp5 = icmp eq i8 %v, 0
call void @use(i1 %cmp5) ; true
ret void

ed:
ret void
}
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