Skip to content

[SimplifyCfg] Handle trunc nuw i1 condition in Equality comparison. #153051

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Aug 17, 2025
Merged

[SimplifyCfg] Handle trunc nuw i1 condition in Equality comparison. #153051

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
e12a2c0
[SimplifyCfg] Add test for trunc nuw i1 condition in Equality compari…
andjo403 Aug 11, 2025
4823fc6
[SimplifyCfg] Handle trunc nuw i1 condition in Equality comparison.
andjo403 Aug 11, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
30 changes: 23 additions & 7 deletions llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -810,11 +810,15 @@ Value *SimplifyCFGOpt::isValueEqualityComparison(Instruction *TI) {
if (!SI->getParent()->hasNPredecessorsOrMore(128 / SI->getNumSuccessors()))
CV = SI->getCondition();
} else if (BranchInst *BI = dyn_cast<BranchInst>(TI))
if (BI->isConditional() && BI->getCondition()->hasOneUse())
if (BI->isConditional() && BI->getCondition()->hasOneUse()) {
if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
if (ICI->isEquality() && getConstantInt(ICI->getOperand(1), DL))
CV = ICI->getOperand(0);
} else if (auto *Trunc = dyn_cast<TruncInst>(BI->getCondition())) {
if (Trunc->hasNoUnsignedWrap())
CV = Trunc->getOperand(0);
}
}

// Unwrap any lossless ptrtoint cast.
if (CV) {
Expand All @@ -840,11 +844,20 @@ BasicBlock *SimplifyCFGOpt::getValueEqualityComparisonCases(
}

BranchInst *BI = cast<BranchInst>(TI);
ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
BasicBlock *Succ = BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_NE);
Cases.push_back(ValueEqualityComparisonCase(
getConstantInt(ICI->getOperand(1), DL), Succ));
return BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_EQ);
Value *Cond = BI->getCondition();
ICmpInst::Predicate Pred;
ConstantInt *C;
if (auto *ICI = dyn_cast<ICmpInst>(Cond)) {
Pred = ICI->getPredicate();
C = getConstantInt(ICI->getOperand(1), DL);
} else {
Pred = ICmpInst::ICMP_NE;
auto *Trunc = cast<TruncInst>(Cond);
C = ConstantInt::get(cast<IntegerType>(Trunc->getOperand(0)->getType()), 0);
}
BasicBlock *Succ = BI->getSuccessor(Pred == ICmpInst::ICMP_NE);
Cases.push_back(ValueEqualityComparisonCase(C, Succ));
return BI->getSuccessor(Pred == ICmpInst::ICMP_EQ);
}

/// Given a vector of bb/value pairs, remove any entries
Expand Down Expand Up @@ -1106,7 +1119,10 @@ static void getBranchWeights(Instruction *TI,
// default weight to be the first entry.
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
assert(Weights.size() == 2);
ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
auto *ICI = dyn_cast<ICmpInst>(BI->getCondition());
if (!ICI)
return;

if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
std::swap(Weights.front(), Weights.back());
}
Expand Down
57 changes: 57 additions & 0 deletions llvm/test/Transforms/SimplifyCFG/switch_create.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1068,3 +1068,60 @@ if:
else:
ret void
}

define void @trunc_nuw_i1_condition(i32 %V) {
; CHECK-LABEL: @trunc_nuw_i1_condition(
; CHECK-NEXT: switch i32 [[V:%.*]], label [[F:%.*]] [
; CHECK-NEXT: i32 2, label [[T:%.*]]
; CHECK-NEXT: i32 0, label [[T]]
; CHECK-NEXT: ]
; CHECK: common.ret:
; CHECK-NEXT: ret void
; CHECK: T:
; CHECK-NEXT: call void @foo1()
; CHECK-NEXT: br label [[COMMON_RET:%.*]]
; CHECK: F:
; CHECK-NEXT: call void @foo2()
; CHECK-NEXT: br label [[COMMON_RET]]
;
%C1 = icmp eq i32 %V, 2
br i1 %C1, label %T, label %N
N:
%C2 = trunc nuw i32 %V to i1
br i1 %C2, label %F, label %T
T:
call void @foo1( )
ret void
F:
call void @foo2( )
ret void
}

define void @neg_trunc_i1_condition(i32 %V) {
; CHECK-LABEL: @neg_trunc_i1_condition(
; CHECK-NEXT: [[C1:%.*]] = icmp ne i32 [[V:%.*]], 2
; CHECK-NEXT: [[C2:%.*]] = trunc i32 [[V]] to i1
; CHECK-NEXT: [[OR_COND:%.*]] = and i1 [[C1]], [[C2]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[F:%.*]], label [[T:%.*]]
; CHECK: common.ret:
; CHECK-NEXT: ret void
; CHECK: T:
; CHECK-NEXT: call void @foo1()
; CHECK-NEXT: br label [[COMMON_RET:%.*]]
; CHECK: F:
; CHECK-NEXT: call void @foo2()
; CHECK-NEXT: br label [[COMMON_RET]]
;
%C1 = icmp eq i32 %V, 2
br i1 %C1, label %T, label %N
N:
%C2 = trunc i32 %V to i1
br i1 %C2, label %F, label %T
T:
call void @foo1( )
ret void
F:
call void @foo2( )
ret void
}