[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). 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
+}
|
fhahn
reviewed
May 5, 2025
| ; 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) |
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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) |
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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
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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).
swift-ci
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May 9, 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). (cherry picked from commit 027b203)
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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).