[BasicAA] Gracefully handle large LocationSize #138528
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If the LocationSize is larger than the index space of the pointer type, bail out instead of triggering an APInt assertion.
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@llvm/pr-subscribers-llvm-analysis Author: Nikita Popov (nikic) ChangesIf the LocationSize is larger than the index space of the pointer type, bail out instead of triggering an APInt assertion. Fixes the issue reported at #119365 (comment). Full diff: https://github.com/llvm/llvm-project/pull/138528.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 2de9bb502baf4..30222b87ea467 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1237,8 +1237,11 @@ AliasResult BasicAAResult::aliasGEP(
if (V1Size.isScalable() || V2Size.isScalable())
return AliasResult::MayAlias;
- // We need to know both acess sizes for all the following heuristics.
- if (!V1Size.hasValue() || !V2Size.hasValue())
+ // We need to know both access sizes for all the following heuristics. Don't
+ // try to reason about sizes larger than the index space.
+ unsigned BW = DecompGEP1.Offset.getBitWidth();
+ if (!V1Size.hasValue() || !V2Size.hasValue() ||
+ !isUIntN(BW, V1Size.getValue()) || !isUIntN(BW, V2Size.getValue()))
return AliasResult::MayAlias;
APInt GCD;
@@ -1293,7 +1296,6 @@ AliasResult BasicAAResult::aliasGEP(
// Compute ranges of potentially accessed bytes for both accesses. If the
// interseciton is empty, there can be no overlap.
- unsigned BW = OffsetRange.getBitWidth();
ConstantRange Range1 = OffsetRange.add(
ConstantRange(APInt(BW, 0), APInt(BW, V1Size.getValue())));
ConstantRange Range2 =
diff --git a/llvm/test/Analysis/BasicAA/size-overflow.ll b/llvm/test/Analysis/BasicAA/size-overflow.ll
new file mode 100644
index 0000000000000..18791ba20ef5f
--- /dev/null
+++ b/llvm/test/Analysis/BasicAA/size-overflow.ll
@@ -0,0 +1,14 @@
+; RUN: opt -passes=aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
+
+target datalayout = "p:32:32"
+
+; Make sure that using a LocationSize larget than the index space does not
+; assert.
+
+; Just Mod: Ptr: i32* %gep <-> call void @llvm.memset.p0.i64(ptr %p, i8 0, i64 68719476736, i1 false)
+define void @test(ptr %p, i32 %idx) {
+ %gep = getelementptr i8, ptr %p, i32 %idx
+ load i32, ptr %gep
+ call void @llvm.memset.i64(ptr %p, i8 0, i64 u0x100000000, i1 false)
+ ret void
+}
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fhahn
reviewed
May 5, 2025
| ; Make sure that using a LocationSize larget than the index space does not | ||
| ; assert. | ||
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||
| ; Just Mod: Ptr: i32* %gep <-> call void @llvm.memset.p0.i64(ptr %p, i8 0, i64 68719476736, i1 false) |
There was a problem hiding this comment.
Missing CHECK below?
Suggested change
| ; Just Mod: Ptr: i32* %gep <-> call void @llvm.memset.p0.i64(ptr %p, i8 0, i64 68719476736, i1 false) | |
| ; CHECK: Just Mod: Ptr: i32* %gep <-> call void @llvm.memset.p0.i64(ptr %p, i8 0, i64 68719476736, i1 false) |
There was a problem hiding this comment.
Oops, looks like I never actually ran the new test...
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/cherry-pick 027b203 |
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/pull-request #138681 |
GeorgeARM
pushed a commit
to GeorgeARM/llvm-project
that referenced
this pull request
May 7, 2025
If the LocationSize is larger than the index space of the pointer type, bail out instead of triggering an APInt assertion. Fixes the issue reported at llvm#119365 (comment).
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If the LocationSize is larger than the index space of the pointer type, bail out instead of triggering an APInt assertion.
Fixes the issue reported at #119365 (comment).