From 824684982968244050e56357e736b9940c23e77d Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Mon, 9 Jun 2008 07:36:11 +0000
Subject: [PATCH] minor changes to short circuit the 'no linkage' case earlier
 for function bodies.  We now don't try to unify types or handling type
 mismatches if when linking an internal foo to an external foo.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52134 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Linker/LinkModules.cpp | 67 +++++++++++++++++++++++---------------
 1 file changed, 40 insertions(+), 27 deletions(-)

diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index 7368c2c0532..a5e9a3e3e8f 100644
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -817,21 +817,47 @@ static bool LinkFunctionProtos(Module *Dest, const Module *Src,
   // Loop over all of the functions in the src module, mapping them over
   for (Module::const_iterator I = Src->begin(), E = Src->end(); I != E; ++I) {
     const Function *SF = I;   // SrcFunction
+    
     Function *DF = 0;
+    
+    // If this function is internal or has no name, it doesn't participate in
+    // linkage.
     if (SF->hasName() && !SF->hasInternalLinkage()) {
       // Check to see if may have to link the function.
       DF = Dest->getFunction(SF->getName());
-      if (DF && SF->getType() != DF->getType())
-        // If types don't agree because of opaque, try to resolve them
-        RecursiveResolveTypes(SF->getType(), DF->getType(), 
-                              &Dest->getTypeSymbolTable(), "");
+      if (DF && DF->hasInternalLinkage())
+        DF = 0;
     }
-
-    if (DF && DF->hasInternalLinkage())
-      DF = NULL;
     
-    // Check visibility
-    if (DF && SF->getVisibility() != DF->getVisibility()) {
+    // If there is no linkage to be performed, just bring over SF without
+    // modifying it.
+    if (DF == 0) {
+      // Function does not already exist, simply insert an function signature
+      // identical to SF into the dest module.
+      Function *NewDF = Function::Create(SF->getFunctionType(),
+                                         SF->getLinkage(),
+                                         SF->getName(), Dest);
+      CopyGVAttributes(NewDF, SF);
+      
+      // If the LLVM runtime renamed the function, but it is an externally
+      // visible symbol, DF must be an existing function with internal linkage.
+      // Rename it.
+      if (!NewDF->hasInternalLinkage() && NewDF->getName() != SF->getName())
+        ForceRenaming(NewDF, SF->getName());
+      
+      // ... and remember this mapping...
+      ValueMap[SF] = NewDF;
+      continue;
+    }
+    
+    
+    // If types don't agree because of opaque, try to resolve them.
+    if (SF->getType() != DF->getType())
+      RecursiveResolveTypes(SF->getType(), DF->getType(), 
+                            &Dest->getTypeSymbolTable(), "");
+    
+    // Check visibility, merging if a definition overrides a prototype.
+    if (SF->getVisibility() != DF->getVisibility()) {
       // If one is a prototype, ignore its visibility.  Prototypes are always
       // overridden by the definition.
       if (!SF->isDeclaration() && !DF->isDeclaration())
@@ -843,7 +869,7 @@ static bool LinkFunctionProtos(Module *Dest, const Module *Src,
         DF->setVisibility(SF->getVisibility());
     }
     
-    if (DF && DF->getType() != SF->getType()) {
+    if (DF->getType() != SF->getType()) {
       if (DF->isDeclaration() && !SF->isDeclaration()) {
         // We have a definition of the same name but different type in the
         // source module. Copy the prototype to the destination and replace
@@ -882,23 +908,10 @@ static bool LinkFunctionProtos(Module *Dest, const Module *Src,
                      ToStr(SF->getFunctionType(), Src) + "' and '" +
                      ToStr(DF->getFunctionType(), Dest) + "'");
       }
-    } else if (!DF || SF->hasInternalLinkage() || DF->hasInternalLinkage()) {
-      // Function does not already exist, simply insert an function signature
-      // identical to SF into the dest module.
-      Function *NewDF = Function::Create(SF->getFunctionType(),
-                                         SF->getLinkage(),
-                                         SF->getName(), Dest);
-      CopyGVAttributes(NewDF, SF);
-
-      // If the LLVM runtime renamed the function, but it is an externally
-      // visible symbol, DF must be an existing function with internal linkage.
-      // Rename it.
-      if (NewDF->getName() != SF->getName() && !NewDF->hasInternalLinkage())
-        ForceRenaming(NewDF, SF->getName());
-
-      // ... and remember this mapping...
-      ValueMap[SF] = NewDF;
-    } else if (SF->isDeclaration()) {
+      continue;
+    }
+    
+    if (SF->isDeclaration()) {
       // If SF is a declaration or if both SF & DF are declarations, just link 
       // the declarations, we aren't adding anything.
       if (SF->hasDLLImportLinkage()) {
-- 
2.34.1