[PATCH] D91482: [BasicAA] Remove unnecessary known size requirement

[Nikita Popov via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG1dea8ed8b7dd: [BasicAA] Remove unnecessary known size requirement (authored by nikic).

Changed prior to commit:
  https://reviews.llvm.org/D91482?vs=306722&id=308144#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D91482/new/

https://reviews.llvm.org/D91482

Files:
  llvm/lib/Analysis/BasicAliasAnalysis.cpp
  llvm/test/Analysis/BasicAA/negoffset.ll


Index: llvm/test/Analysis/BasicAA/negoffset.ll
===================================================================
--- llvm/test/Analysis/BasicAA/negoffset.ll
+++ llvm/test/Analysis/BasicAA/negoffset.ll
@@ -117,3 +117,13 @@
   %2 = load i32, i32* %1
   ret i32 %2
 }
+
+; CHECK-LABEL: Function: one_size_unknown:
+; CHECK: NoModRef:  Ptr: i8* %p.minus1	<->  call void @llvm.memset.p0i8.i32(i8* %p, i8 0, i32 %size, i1 false)
+define void @one_size_unknown(i8* %p, i32 %size) {
+  %p.minus1 = getelementptr inbounds i8, i8* %p, i32 -1
+  call void @llvm.memset.p0i8.i32(i8* %p, i8 0, i32 %size, i1 false)
+  ret void
+}
+
+declare void @llvm.memset.p0i8.i32(i8*, i8, i32, i1)
Index: llvm/lib/Analysis/BasicAliasAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1336,9 +1336,7 @@
       // ---------------->|
       // |-->V1Size       |-------> V2Size
       // GEP1             V2
-      // We need to know that V2Size is not unknown, otherwise we might have
-      // stripped a gep with negative index ('gep <ptr>, -1, ...).
-      if (V1Size.hasValue() && V2Size.hasValue()) {
+      if (V1Size.hasValue()) {
         if ((-DecompGEP1.Offset).ult(V1Size.getValue()))
           return PartialAlias;
         return NoAlias;


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