From ac45c9171d164af8737f56bbde3370318401d1a3 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Sat, 31 Oct 2009 14:32:25 +0000
Subject: [PATCH] Make ScalarEvolutionAliasAnalysis slightly more aggressive,
 by making an underlying alias call even for non-identified-object values.

llvm-svn: 85656
---
 .../Analysis/ScalarEvolutionAliasAnalysis.cpp | 23 ++++++++-----------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/llvm/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp b/llvm/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp
index 924e2dcd5edd..ef0e97b6e10e 100644
--- a/llvm/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/ScalarEvolutionAliasAnalysis.cpp
@@ -38,7 +38,7 @@ namespace {
     virtual AliasResult alias(const Value *V1, unsigned V1Size,
                               const Value *V2, unsigned V2Size);
 
-    Value *GetUnderlyingIdentifiedObject(const SCEV *S);
+    Value *GetBaseValue(const SCEV *S);
   };
 }  // End of anonymous namespace
 
@@ -68,25 +68,22 @@ ScalarEvolutionAliasAnalysis::runOnFunction(Function &F) {
   return false;
 }
 
-/// GetUnderlyingIdentifiedObject - Given an expression, try to find an
-/// "identified object" (see AliasAnalysis::isIdentifiedObject) base
-/// value. Return null is none was found.
+/// GetBaseValue - Given an expression, try to find a
+/// base value. Return null is none was found.
 Value *
-ScalarEvolutionAliasAnalysis::GetUnderlyingIdentifiedObject(const SCEV *S) {
+ScalarEvolutionAliasAnalysis::GetBaseValue(const SCEV *S) {
   if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
     // In an addrec, assume that the base will be in the start, rather
     // than the step.
-    return GetUnderlyingIdentifiedObject(AR->getStart());
+    return GetBaseValue(AR->getStart());
   } else if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
     // If there's a pointer operand, it'll be sorted at the end of the list.
     const SCEV *Last = A->getOperand(A->getNumOperands()-1);
     if (isa<PointerType>(Last->getType()))
-      return GetUnderlyingIdentifiedObject(Last);
+      return GetBaseValue(Last);
   } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
-    // Determine if we've found an Identified object.
-    Value *V = U->getValue();
-    if (isIdentifiedObject(V))
-      return V;
+    // This is a leaf node.
+    return U->getValue();
   }
   // No Identified object found.
   return 0;
@@ -120,8 +117,8 @@ ScalarEvolutionAliasAnalysis::alias(const Value *A, unsigned ASize,
   // If ScalarEvolution can find an underlying object, form a new query.
   // The correctness of this depends on ScalarEvolution not recognizing
   // inttoptr and ptrtoint operators.
-  Value *AO = GetUnderlyingIdentifiedObject(AS);
-  Value *BO = GetUnderlyingIdentifiedObject(BS);
+  Value *AO = GetBaseValue(AS);
+  Value *BO = GetBaseValue(BS);
   if ((AO && AO != A) || (BO && BO != B))
     if (alias(AO ? AO : A, AO ? ~0u : ASize,
               BO ? BO : B, BO ? ~0u : BSize) == NoAlias)