[llvm] 9071393 - [GlobalDCE] Simplify and return Changed = true less often

[Jay Foad via llvm-commits]

Author: Jay Foad
Date: 2022-02-17T16:03:13Z
New Revision: 9071393c18e5264e3bbf3ca3f3584fa5f45be6c2

URL: https://github.com/llvm/llvm-project/commit/9071393c18e5264e3bbf3ca3f3584fa5f45be6c2
DIFF: https://github.com/llvm/llvm-project/commit/9071393c18e5264e3bbf3ca3f3584fa5f45be6c2.diff

LOG: [GlobalDCE] Simplify and return Changed = true less often

Removing dead constants should not count as making a change to the
module. This means that RemoveUnusedGlobalValue simplifies to just
calling removeDeadConstantUsers, so inline it.

Differential Revision: https://reviews.llvm.org/D120052

Added: 
    

Modified: 
    llvm/lib/Transforms/IPO/GlobalDCE.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/IPO/GlobalDCE.cpp b/llvm/lib/Transforms/IPO/GlobalDCE.cpp
index 5e5d2086adc2e..e375504099610 100644
--- a/llvm/lib/Transforms/IPO/GlobalDCE.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalDCE.cpp
@@ -317,7 +317,7 @@ PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
 
   // Loop over the module, adding globals which are obviously necessary.
   for (GlobalObject &GO : M.global_objects()) {
-    Changed |= RemoveUnusedGlobalValue(GO);
+    GO.removeDeadConstantUsers();
     // Functions with external linkage are needed if they have a body.
     // Externally visible & appending globals are needed, if they have an
     // initializer.
@@ -330,7 +330,7 @@ PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
 
   // Compute direct dependencies of aliases.
   for (GlobalAlias &GA : M.aliases()) {
-    Changed |= RemoveUnusedGlobalValue(GA);
+    GA.removeDeadConstantUsers();
     // Externally visible aliases are needed.
     if (!GA.isDiscardableIfUnused())
       MarkLive(GA);
@@ -340,7 +340,7 @@ PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
 
   // Compute direct dependencies of ifuncs.
   for (GlobalIFunc &GIF : M.ifuncs()) {
-    Changed |= RemoveUnusedGlobalValue(GIF);
+    GIF.removeDeadConstantUsers();
     // Externally visible ifuncs are needed.
     if (!GIF.isDiscardableIfUnused())
       MarkLive(GIF);
@@ -403,7 +403,7 @@ PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
   // Now that all interferences have been dropped, delete the actual objects
   // themselves.
   auto EraseUnusedGlobalValue = [&](GlobalValue *GV) {
-    RemoveUnusedGlobalValue(*GV);
+    GV->removeDeadConstantUsers();
     GV->eraseFromParent();
     Changed = true;
   };
@@ -455,16 +455,3 @@ PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
     return PreservedAnalyses::none();
   return PreservedAnalyses::all();
 }
-
-// RemoveUnusedGlobalValue - Loop over all of the uses of the specified
-// GlobalValue, looking for the constant pointer ref that may be pointing to it.
-// If found, check to see if the constant pointer ref is safe to destroy, and if
-// so, nuke it.  This will reduce the reference count on the global value, which
-// might make it deader.
-//
-bool GlobalDCEPass::RemoveUnusedGlobalValue(GlobalValue &GV) {
-  if (GV.use_empty())
-    return false;
-  GV.removeDeadConstantUsers();
-  return GV.use_empty();
-}