release/20.x: [BasicAA] Gracefully handle large LocationSize (#138528) #138681
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@fhahn What do you think about merging this PR to the release branch? |
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@llvm/pr-subscribers-llvm-analysis Author: None (llvmbot) ChangesBackport 027b203 Requested by: @nikic Full diff: https://github.com/llvm/llvm-project/pull/138681.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index b2a3f3390e000..06e8eb7072917 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1245,8 +1245,11 @@ 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;
@@ -1301,7 +1304,6 @@ 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..2a390d29e472a
--- /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 < %s 2>&1 | FileCheck %s
+
+target datalayout = "p:32:32"
+
+; Make sure that using a LocationSize larget than the index space does not
+; assert.
+
+; CHECK: Just Mod: Ptr: i32* %gep <-> call void @llvm.memset.p0.i64(ptr %p, i8 0, i64 4294967296, 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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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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@nikic (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR. |
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Backport 027b203
Requested by: @nikic