From a9b60ee0fc6e8265b4b2656f8ad23e187981d5bd Mon Sep 17 00:00:00 2001
From: Anton Korobeynikov <asl@math.spbu.ru>
Date: Tue, 9 Sep 2008 19:04:59 +0000
Subject: Resolve aliases, when possible

llvm-svn: 56001
---
 llvm/lib/Transforms/IPO/GlobalOpt.cpp | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

(limited to 'llvm/lib/Transforms/IPO')

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index f9a7c73534b..8c6631aa2bc 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -65,6 +65,7 @@ namespace {
     GlobalVariable *FindGlobalCtors(Module &M);
     bool OptimizeFunctions(Module &M);
     bool OptimizeGlobalVars(Module &M);
+    bool ResolveAliases(Module &M);
     bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
     bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
   };
@@ -2214,6 +2215,23 @@ bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
   return true;
 }
 
+bool GlobalOpt::ResolveAliases(Module &M) {
+  bool Changed = false;
+
+  for (Module::alias_iterator I = M.alias_begin(),
+         E = M.alias_end(); I != E; ++I) {
+    if (I->use_empty())
+      continue;
+
+    if (const GlobalValue *GV = I->resolveAliasedGlobal(/*traverseWeak*/ false))
+      if (GV != I) {
+        I->replaceAllUsesWith(const_cast<GlobalValue*>(GV));
+        Changed = true;
+      }
+  }
+
+  return Changed;
+}
 
 bool GlobalOpt::runOnModule(Module &M) {
   bool Changed = false;
@@ -2235,6 +2253,10 @@ bool GlobalOpt::runOnModule(Module &M) {
     // Optimize non-address-taken globals.
     LocalChange |= OptimizeGlobalVars(M);
     Changed |= LocalChange;
+
+    // Resolve aliases, when possible.
+    LocalChange |= ResolveAliases(M);
+    Changed |= LocalChange;
   }
   
   // TODO: Move all global ctors functions to the end of the module for code
-- 
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