Skip to content

[ValueTracking] Teach isGuaranteedNotToBeUndefOrPoison about splats #163570

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 4 commits into from
Oct 20, 2025
Merged

[ValueTracking] Teach isGuaranteedNotToBeUndefOrPoison about splats #163570

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
c8cdc8c
[ValueTracking] Teach isGuaranteedNotToBeUndefOrPoison about splats
c-rhodes Oct 10, 2025
ec52263
address comments
c-rhodes Oct 15, 2025
6cfa5ae
address comments
c-rhodes Oct 16, 2025
7bf81c7
address comments
c-rhodes Oct 16, 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
5 changes: 5 additions & 0 deletions llvm/lib/Analysis/ValueTracking.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -7678,6 +7678,7 @@ static bool isGuaranteedNotToBeUndefOrPoison(
return true;
}

Value *Splat;
if (!::canCreateUndefOrPoison(Opr, Kind,
/*ConsiderFlagsAndMetadata=*/true)) {
if (const auto *PN = dyn_cast<PHINode>(V)) {
Expand All @@ -7695,6 +7696,10 @@ static bool isGuaranteedNotToBeUndefOrPoison(
}
if (IsWellDefined)
return true;
} else if (isa<ShuffleVectorInst>(Opr) && (Splat = getSplatValue(Opr))) {
// For splats we only need to check the value being splatted.
if (OpCheck(Splat))
return true;
} else if (all_of(Opr->operands(), OpCheck))
return true;
}
Expand Down
10 changes: 10 additions & 0 deletions llvm/unittests/Analysis/ValueTrackingTest.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1091,6 +1091,16 @@ TEST_F(ValueTrackingTest, isGuaranteedNotToBeUndefOrPoison) {
}
}

TEST_F(ValueTrackingTest, isGuaranteedNotToBeUndefOrPoison_splat) {
parseAssembly(
"define <4 x i32> @test(i32 noundef %x) {\n"
" %ins = insertelement <4 x i32> poison, i32 %x, i32 0\n"
" %A = shufflevector <4 x i32> %ins, <4 x i32> poison, <4 x i32> zeroinitializer\n"
" ret <4 x i32> %A\n"
"}");
EXPECT_TRUE(isGuaranteedNotToBeUndefOrPoison(A));
}

TEST_F(ValueTrackingTest, isGuaranteedNotToBeUndefOrPoison_assume) {
parseAssembly("declare i1 @f_i1()\n"
"declare i32 @f_i32()\n"
Expand Down
Loading