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[ValueTracking] Handle not in isImpliedCondition #85397

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Merged
merged 2 commits into from
Mar 20, 2024
Merged

[ValueTracking] Handle not in isImpliedCondition #85397

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ff55eba
[ValueTracking] Add pre-commit tests. NFC.
dtcxzyw Mar 15, 2024
0cc2a01
[ValueTracking] Handle not in `isImpliedCondition`
dtcxzyw Mar 15, 2024
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31 changes: 23 additions & 8 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8622,6 +8622,10 @@ llvm::isImpliedCondition(const Value *LHS, CmpInst::Predicate RHSPred,
assert(LHS->getType()->isIntOrIntVectorTy(1) &&
"Expected integer type only!");

// Match not
if (match(LHS, m_Not(m_Value(LHS))))
LHSIsTrue = !LHSIsTrue;

// Both LHS and RHS are icmps.
const ICmpInst *LHSCmp = dyn_cast<ICmpInst>(LHS);
if (LHSCmp)
Expand All @@ -8648,10 +8652,21 @@ std::optional<bool> llvm::isImpliedCondition(const Value *LHS, const Value *RHS,
if (LHS == RHS)
return LHSIsTrue;

if (const ICmpInst *RHSCmp = dyn_cast<ICmpInst>(RHS))
return isImpliedCondition(LHS, RHSCmp->getPredicate(),
RHSCmp->getOperand(0), RHSCmp->getOperand(1), DL,
LHSIsTrue, Depth);
// Match not
bool InvertRHS = false;
if (match(RHS, m_Not(m_Value(RHS)))) {
if (LHS == RHS)
return !LHSIsTrue;
InvertRHS = true;
}

if (const ICmpInst *RHSCmp = dyn_cast<ICmpInst>(RHS)) {
if (auto Implied = isImpliedCondition(
LHS, RHSCmp->getPredicate(), RHSCmp->getOperand(0),
RHSCmp->getOperand(1), DL, LHSIsTrue, Depth))
return InvertRHS ? !*Implied : *Implied;
return std::nullopt;
}

if (Depth == MaxAnalysisRecursionDepth)
return std::nullopt;
Expand All @@ -8663,21 +8678,21 @@ std::optional<bool> llvm::isImpliedCondition(const Value *LHS, const Value *RHS,
if (std::optional<bool> Imp =
isImpliedCondition(LHS, RHS1, DL, LHSIsTrue, Depth + 1))
if (*Imp == true)
return true;
return !InvertRHS;
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@dtcxzyw dtcxzyw Mar 15, 2024 •
edited
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Oh, it looks incorrect :(

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Its confusing enough I think it deserves a comment.

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NB: I don't any of your tests actually go through this control flow

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Just a heads up, im working on a follow up patch to this to handle more of the and/or cases + more relationships in general (LMK if you are so we can avoid duplicating work).

if (std::optional<bool> Imp =
isImpliedCondition(LHS, RHS2, DL, LHSIsTrue, Depth + 1))
if (*Imp == true)
return true;
return !InvertRHS;
}
if (match(RHS, m_LogicalAnd(m_Value(RHS1), m_Value(RHS2)))) {
if (std::optional<bool> Imp =
isImpliedCondition(LHS, RHS1, DL, LHSIsTrue, Depth + 1))
if (*Imp == false)
return false;
return InvertRHS;
if (std::optional<bool> Imp =
isImpliedCondition(LHS, RHS2, DL, LHSIsTrue, Depth + 1))
if (*Imp == false)
return false;
return InvertRHS;
}

return std::nullopt;
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69 changes: 69 additions & 0 deletions llvm/test/Transforms/InstCombine/and-or-implied-cond-not.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,69 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
; RUN: opt < %s -passes=instcombine -S | FileCheck %s

define i1 @test_imply_not1(i32 %depth) {
; CHECK-LABEL: define i1 @test_imply_not1(
; CHECK-SAME: i32 [[DEPTH:%.*]]) {
; CHECK-NEXT: [[CMP1_NOT1:%.*]] = icmp eq i32 [[DEPTH]], 16
; CHECK-NEXT: call void @use(i1 [[CMP1_NOT1]])
; CHECK-NEXT: [[CMP2:%.*]] = icmp slt i32 [[DEPTH]], 8
; CHECK-NEXT: call void @use(i1 [[CMP2]])
; CHECK-NEXT: br i1 [[CMP1_NOT1]], label [[IF_ELSE:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: call void @func1()
; CHECK-NEXT: unreachable
; CHECK: if.else:
; CHECK-NEXT: call void @func2()
; CHECK-NEXT: unreachable
;
%cmp1 = icmp eq i32 %depth, 16
call void @use(i1 %cmp1)
%cmp2 = icmp slt i32 %depth, 8
call void @use(i1 %cmp2)
%cmp.not = xor i1 %cmp1, true
%brmerge = or i1 %cmp2, %cmp.not
br i1 %brmerge, label %if.then, label %if.else
if.then:
call void @func1()
unreachable

if.else:
call void @func2()
unreachable
}

define i1 @test_imply_not2(i32 %a, i1 %cmp2) {
; CHECK-LABEL: define i1 @test_imply_not2(
; CHECK-SAME: i32 [[A:%.*]], i1 [[CMP2:%.*]]) {
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i32 [[A]], 0
; CHECK-NEXT: [[BRMERGE:%.*]] = select i1 [[CMP1]], i1 true, i1 [[CMP2]]
; CHECK-NEXT: ret i1 [[BRMERGE]]
;
%cmp1 = icmp eq i32 %a, 0
%or.cond = select i1 %cmp1, i1 %cmp2, i1 false
%cmp.not = xor i1 %cmp1, true
%brmerge = or i1 %or.cond, %cmp.not
ret i1 %brmerge
}

define i1 @test_imply_not3(i32 %a, i32 %b, i1 %cond) {
; CHECK-LABEL: define i1 @test_imply_not3(
; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]], i1 [[COND:%.*]]) {
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[A]], [[B]]
; CHECK-NEXT: call void @use(i1 [[CMP1]])
; CHECK-NEXT: [[CMP2:%.*]] = icmp slt i32 [[A]], [[B]]
; CHECK-NEXT: [[AND:%.*]] = select i1 [[CMP2]], i1 [[COND]], i1 false
; CHECK-NEXT: ret i1 [[AND]]
;
%cmp1 = icmp eq i32 %a, %b
call void @use(i1 %cmp1)
%cmp2 = icmp slt i32 %a, %b
%cmp.not = xor i1 %cmp1, true
%sel = select i1 %cmp.not, i1 %cond, i1 false
%and = and i1 %cmp2, %sel
ret i1 %and
}

declare void @func1()
declare void @func2()
declare void @use(i1)
3 changes: 1 addition & 2 deletions llvm/test/Transforms/LoopVectorize/reduction-inloop.ll
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Expand Up @@ -1354,9 +1354,8 @@ define i32 @predicated_or_dominates_reduction(ptr %b) {
; CHECK: pred.load.continue6:
; CHECK-NEXT: [[TMP43:%.*]] = phi <4 x i32> [ [[TMP37]], [[PRED_LOAD_CONTINUE4]] ], [ [[TMP42]], [[PRED_LOAD_IF5]] ]
; CHECK-NEXT: [[TMP44:%.*]] = icmp ne <4 x i32> [[TMP43]], zeroinitializer
; CHECK-NEXT: [[TMP45:%.*]] = select <4 x i1> [[TMP19]], <4 x i1> [[TMP44]], <4 x i1> zeroinitializer
; CHECK-NEXT: [[TMP46:%.*]] = xor <4 x i1> [[TMP19]], <i1 true, i1 true, i1 true, i1 true>
; CHECK-NEXT: [[TMP47:%.*]] = or <4 x i1> [[TMP45]], [[TMP46]]
; CHECK-NEXT: [[TMP47:%.*]] = select <4 x i1> [[TMP46]], <4 x i1> <i1 true, i1 true, i1 true, i1 true>, <4 x i1> [[TMP44]]
; CHECK-NEXT: [[TMP48:%.*]] = bitcast <4 x i1> [[TMP47]] to i4
; CHECK-NEXT: [[TMP49:%.*]] = call i4 @llvm.ctpop.i4(i4 [[TMP48]]), !range [[RNG42:![0-9]+]]
; CHECK-NEXT: [[TMP50:%.*]] = zext nneg i4 [[TMP49]] to i32
Expand Down