From 4f77caaa3d2265d69a52bd6a4e5905504896c220 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Thu, 26 Feb 2004 20:02:23 +0000
Subject: [PATCH] Since LLVM uses structure type equivalence, it isn't useful
 to keep around multiple type names for the same structural type.  Make DTE
 eliminate all but one of the type names

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11879 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/IPO/DeadTypeElimination.cpp | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/lib/Transforms/IPO/DeadTypeElimination.cpp b/lib/Transforms/IPO/DeadTypeElimination.cpp
index 8849a025a0a..c3a9f6edc5b 100644
--- a/lib/Transforms/IPO/DeadTypeElimination.cpp
+++ b/lib/Transforms/IPO/DeadTypeElimination.cpp
@@ -49,12 +49,12 @@ Pass *llvm::createDeadTypeEliminationPass() {
 // ShouldNukeSymtabEntry - Return true if this module level symbol table entry
 // should be eliminated.
 //
-static inline bool ShouldNukeSymtabEntry(const std::pair<std::string,Value*>&E){
+static inline bool ShouldNukeSymtabEntry(const Type *Ty){
   // Nuke all names for primitive types!
-  if (cast<Type>(E.second)->isPrimitiveType()) return true;
+  if (Ty->isPrimitiveType()) return true;
 
   // Nuke all pointers to primitive types as well...
-  if (const PointerType *PT = dyn_cast<PointerType>(E.second))
+  if (const PointerType *PT = dyn_cast<PointerType>(Ty))
     if (PT->getElementType()->isPrimitiveType()) return true;
 
   return false;
@@ -69,8 +69,7 @@ bool DTE::run(Module &M) {
   bool Changed = false;
 
   SymbolTable &ST = M.getSymbolTable();
-  const std::set<const Type *> &UsedTypes =
-    getAnalysis<FindUsedTypes>().getTypes();
+  std::set<const Type *> UsedTypes = getAnalysis<FindUsedTypes>().getTypes();
 
   // Check the symbol table for superfluous type entries...
   //
@@ -79,18 +78,20 @@ bool DTE::run(Module &M) {
   if (STI != ST.end()) {
     // Loop over all entries in the type plane...
     SymbolTable::VarMap &Plane = STI->second;
-    for (SymbolTable::VarMap::iterator PI = Plane.begin(); PI != Plane.end();)
+    for (SymbolTable::VarMap::iterator PI = Plane.begin(); PI != Plane.end();) {
       // If this entry should be unconditionally removed, or if we detect that
       // the type is not used, remove it.
-      if (ShouldNukeSymtabEntry(*PI) ||
-          !UsedTypes.count(cast<Type>(PI->second))) {
-        SymbolTable::VarMap::iterator PJ = PI++;
-        Plane.erase(PJ);
+      const Type *RHS = cast<Type>(PI->second);
+      if (ShouldNukeSymtabEntry(RHS) || !UsedTypes.count(RHS)) {
+        Plane.erase(PI++);
         ++NumKilled;
         Changed = true;
       } else {
         ++PI;
+        // We only need to leave one name for each type.
+        UsedTypes.erase(RHS);
       }
+    }
   }
 
   return Changed;
-- 
2.34.1