From 392249fcf368a22f48091a16c180160221c7e89a Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor@mac.com>
Date: Mon, 3 Jan 2011 23:51:43 +0000
Subject: [PATCH] Use the new addEscapingValue callback to update GlobalsModRef
 when GVN adds PHIs of GEPs. For the moment, have GlobalsModRef handle this
 conservatively by simply removing the value from its maps.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122787 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/IPA/GlobalsModRef.cpp | 11 +++++++++++
 lib/Analysis/NoAliasAnalysis.cpp   |  1 +
 lib/Transforms/Scalar/GVN.cpp      | 21 +++++++++++++++++++--
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/lib/Analysis/IPA/GlobalsModRef.cpp b/lib/Analysis/IPA/GlobalsModRef.cpp
index c18dc47406a..116aaf418ea 100644
--- a/lib/Analysis/IPA/GlobalsModRef.cpp
+++ b/lib/Analysis/IPA/GlobalsModRef.cpp
@@ -152,6 +152,7 @@ namespace {
 
     virtual void deleteValue(Value *V);
     virtual void copyValue(Value *From, Value *To);
+    virtual void addEscapingUse(Use &U);
 
     /// getAdjustedAnalysisPointer - This method is used when a pass implements
     /// an analysis interface through multiple inheritance.  If needed, it
@@ -596,3 +597,13 @@ void GlobalsModRef::deleteValue(Value *V) {
 void GlobalsModRef::copyValue(Value *From, Value *To) {
   AliasAnalysis::copyValue(From, To);
 }
+
+void GlobalsModRef::addEscapingUse(Use &U) {
+  // For the purposes of this analysis, it is conservatively correct to treat
+  // a newly escaping value equivalently to a deleted one.  We could perhaps
+  // be more precise by processing the new use and attempting to update our
+  // saved analysis results to accomodate it.
+  deleteValue(U);
+  
+  AliasAnalysis::addEscapingUse(U);
+}
diff --git a/lib/Analysis/NoAliasAnalysis.cpp b/lib/Analysis/NoAliasAnalysis.cpp
index ab7a69241e9..101c2d5b028 100644
--- a/lib/Analysis/NoAliasAnalysis.cpp
+++ b/lib/Analysis/NoAliasAnalysis.cpp
@@ -65,6 +65,7 @@ namespace {
 
     virtual void deleteValue(Value *V) {}
     virtual void copyValue(Value *From, Value *To) {}
+    virtual void addEscapingUse(Use &U) {}
     
     /// getAdjustedAnalysisPointer - This method is used when a pass implements
     /// an analysis interface through multiple inheritance.  If needed, it
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index bf46bd98c3d..f0e0f381425 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -1063,6 +1063,15 @@ static Value *ConstructSSAForLoadSet(LoadInst *LI,
   if (V->getType()->isPointerTy())
     for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
       AA->copyValue(LI, NewPHIs[i]);
+    
+    // Now that we've copied information to the new PHIs, scan through
+    // them again and inform alias analysis that we've added potentially
+    // escaping uses to any values that are operands to these PHIs.
+    for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i) {
+      PHINode *P = NewPHIs[i];
+      for (unsigned ii = 0, ee = P->getNumIncomingValues(); ii != ee; ++ii)
+        AA->addEscapingUse(P->getOperandUse(2*ii));
+    }
 
   return V;
 }
@@ -1957,8 +1966,16 @@ bool GVN::performPRE(Function &F) {
       insert_table(ValNo, Phi, CurrentBlock);
 
       CurInst->replaceAllUsesWith(Phi);
-      if (MD && Phi->getType()->isPointerTy())
-        MD->invalidateCachedPointerInfo(Phi);
+      if (Phi->getType()->isPointerTy()) {
+        // Because we have added a PHI-use of the pointer value, it has now
+        // "escaped" from alias analysis' perspective.  We need to inform
+        // AA of this.
+        for (unsigned ii = 0, ee = Phi->getNumIncomingValues(); ii != ee; ++ii)
+          VN.getAliasAnalysis()->addEscapingUse(Phi->getOperandUse(2*ii));
+        
+        if (MD)
+          MD->invalidateCachedPointerInfo(Phi);
+      }
       VN.erase(CurInst);
       erase_table(ValNo, CurInst, CurrentBlock);
 
-- 
2.34.1