[llvm] 608ee70 - [SCEV] Ensure SCEV does not replace aliases with their aliasees

[Leonard Chan via llvm-commits]

Author: Leonard Chan
Date: 2023-02-23T19:59:25Z
New Revision: 608ee703e530b00130923417b6663c9f3816f889

URL: https://github.com/llvm/llvm-project/commit/608ee703e530b00130923417b6663c9f3816f889
DIFF: https://github.com/llvm/llvm-project/commit/608ee703e530b00130923417b6663c9f3816f889.diff

LOG: [SCEV] Ensure SCEV does not replace aliases with their aliasees

Passes in general shouldn't replace an alias with the aliasee (see
https://reviews.llvm.org/D66606). This can lead to situations where a
linkonce_odr symbol (which could be interposable if lowered to weak
linkage) can be replaced with a local aliasee which won't be
interposable. SVEC does this when the function is invoked by
FunctionPass Manager -> Loop Pass Manager -> Induction Variable Users in
the codegen pipeline. This was found in hwasan instrumented code where a
linonce_odr alias was replaced with its private aliasee.

This fixes the bug descriped at
https://github.com/llvm/llvm-project/issues/60668.

Differential Revision: https://reviews.llvm.org/D144035

Added: 
    llvm/test/Analysis/ScalarEvolution/no-follow-alias.ll

Modified: 
    llvm/lib/Analysis/ScalarEvolution.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 5c2c12c7d0591..93c9349b06b82 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -7429,10 +7429,6 @@ ScalarEvolution::getOperandsToCreate(Value *V, SmallVectorImpl<Value *> &Ops) {
   } else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
     return getConstant(CI);
   else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
-    if (!GA->isInterposable()) {
-      Ops.push_back(GA->getAliasee());
-      return nullptr;
-    }
     return getUnknown(V);
   } else if (!isa<ConstantExpr>(V))
     return getUnknown(V);
@@ -7619,7 +7615,7 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
   } else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
     return getConstant(CI);
   else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
-    return GA->isInterposable() ? getUnknown(V) : getSCEV(GA->getAliasee());
+    return getUnknown(V);
   else if (!isa<ConstantExpr>(V))
     return getUnknown(V);
 

diff  --git a/llvm/test/Analysis/ScalarEvolution/no-follow-alias.ll b/llvm/test/Analysis/ScalarEvolution/no-follow-alias.ll
new file mode 100644
index 0000000000000..d4d0b7afbdbc8
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/no-follow-alias.ll
@@ -0,0 +1,19 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
+; RUN: opt -passes='print<scalar-evolution>' -disable-output %s 2>&1 | FileCheck %s
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown-linux-gnu"
+
+ at glob.private = private constant [32 x i32] zeroinitializer
+ at glob = linkonce_odr hidden alias [32 x i32], inttoptr (i64 add (i64 ptrtoint (ptr @glob.private to i64), i64 1234) to ptr)
+
+define hidden void @func(i64 %idx) local_unnamed_addr {
+; CHECK-LABEL: 'func'
+; CHECK-NEXT:  Classifying expressions for: @func
+; CHECK-NEXT:    %arrayidx = getelementptr inbounds [32 x i32], ptr @glob, i64 0, i64 %idx
+; CHECK-NEXT:    --> ((4 * %idx) + @glob) U: [0,-1) S: [-9223372036854775808,9223372036854775807)
+; CHECK-NEXT:  Determining loop execution counts for: @func
+;
+  %arrayidx = getelementptr inbounds [32 x i32], ptr @glob, i64 0, i64 %idx
+  ret void
+}