[PATCH] D144468: [GlobalOpt] Extend CleanupPointerRootUsers to handle CE users.

[Florian Hahn via Phabricator via llvm-commits]

fhahn updated this revision to Diff 501063.
fhahn marked an inline comment as done.
fhahn added a comment.
Herald added a subscriber: steven_wu.

Rebase on top of  c34936465c5648f825414fe76ccad7a9ad82dddd <https://reviews.llvm.org/rGc34936465c5648f825414fe76ccad7a9ad82dddd> which adds a test with non GEP constant expressions.

Also update ThinLTO test.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D144468/new/

https://reviews.llvm.org/D144468

Files:
  llvm/lib/Transforms/IPO/GlobalOpt.cpp
  llvm/test/ThinLTO/X86/import-constant.ll
  llvm/test/Transforms/GlobalOpt/cleanup-pointer-root-users-gep-constexpr.ll


Index: llvm/test/Transforms/GlobalOpt/cleanup-pointer-root-users-gep-constexpr.ll
===================================================================
--- llvm/test/Transforms/GlobalOpt/cleanup-pointer-root-users-gep-constexpr.ll
+++ llvm/test/Transforms/GlobalOpt/cleanup-pointer-root-users-gep-constexpr.ll
@@ -16,14 +16,6 @@
 define void @stores_single_use_gep_constexpr() {
 ; CHECK-LABEL: @stores_single_use_gep_constexpr(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    store ptr @fn1, ptr getelementptr inbounds ([[STRUCT_GLOBAL_20PTR:%.*]], ptr @global.20ptr, i64 0, i32 1), align 8
-; CHECK-NEXT:    store ptr @fn2, ptr getelementptr inbounds ([[STRUCT_GLOBAL_20PTR]], ptr @global.20ptr, i64 0, i32 2), align 8
-; CHECK-NEXT:    store ptr @fn3, ptr getelementptr inbounds ([[STRUCT_GLOBAL_20PTR]], ptr @global.20ptr, i64 0, i32 3), align 8
-; CHECK-NEXT:    store ptr @fn0, ptr getelementptr inbounds ([[STRUCT_GLOBAL_20PTR]], ptr @global.20ptr, i64 0, i32 4), align 8
-; CHECK-NEXT:    store ptr @fn1, ptr getelementptr inbounds ([[STRUCT_GLOBAL_20PTR]], ptr @global.20ptr, i64 0, i32 5), align 8
-; CHECK-NEXT:    store ptr @fn2, ptr getelementptr inbounds ([[STRUCT_GLOBAL_20PTR]], ptr @global.20ptr, i64 0, i32 6), align 8
-; CHECK-NEXT:    store ptr @fn3, ptr getelementptr inbounds ([[STRUCT_GLOBAL_20PTR]], ptr @global.20ptr, i64 0, i32 7), align 8
-; CHECK-NEXT:    store ptr @fn0, ptr getelementptr inbounds ([[STRUCT_GLOBAL_20PTR]], ptr @global.20ptr, i64 0, i32 8), align 8
 ; CHECK-NEXT:    ret void
 ;
 entry:
@@ -42,8 +34,6 @@
 define void @stores_multi_use_gep_constexpr() {
 ; CHECK-LABEL: @stores_multi_use_gep_constexpr(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    store i32 0, ptr getelementptr inbounds ([[STRUCT_GLOBAL_20PTR:%.*]], ptr @global.20ptr, i64 0, i32 16), align 8
-; CHECK-NEXT:    store i32 0, ptr getelementptr inbounds ([[STRUCT_GLOBAL_20PTR]], ptr @global.20ptr, i64 0, i32 16), align 8
 ; CHECK-NEXT:    ret void
 ;
 entry:
Index: llvm/test/ThinLTO/X86/import-constant.ll
===================================================================
--- llvm/test/ThinLTO/X86/import-constant.ll
+++ llvm/test/ThinLTO/X86/import-constant.ll
@@ -32,11 +32,11 @@
 ; IMPORT-NEXT: @_ZL3Obj.llvm.{{.*}} = available_externally hidden constant %struct.S { i32 4, i32 8, ptr @val }
 ; IMPORT-NEXT: @outer = internal local_unnamed_addr global %struct.Q zeroinitializer
 
-; OPT: @outer = internal unnamed_addr global %struct.Q zeroinitializer
+; @outer is a write-only variable that's stored to once, so the store and the global can be removed.
+; OPT-NOT: @outer
 
 ; OPT:      define dso_local i32 @main()
 ; OPT-NEXT: entry:
-; OPT-NEXT:   store ptr null, ptr getelementptr inbounds (%struct.Q, ptr @outer, i64 1, i32 0)
 ; OPT-NEXT:   ret i32 12
 
 ; NOREFS:      @_ZL3Obj.llvm.{{.*}} = external hidden constant %struct.S
Index: llvm/lib/Transforms/IPO/GlobalOpt.cpp
===================================================================
--- llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -206,8 +206,13 @@
   // chain of computation and the store to the global in Dead[n].second.
   SmallVector<std::pair<Instruction *, Instruction *>, 32> Dead;
 
+  SmallVector<User *> Worklist(GV->users());
+  SmallPtrSet<User *, 8> Seen;
   // Constants can't be pointers to dynamically allocated memory.
-  for (User *U : llvm::make_early_inc_range(GV->users())) {
+  while (!Worklist.empty()) {
+    User *U = Worklist.pop_back_val();
+    if (!Seen.insert(U).second)
+      continue;
     if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
       Value *V = SI->getValueOperand();
       if (isa<Constant>(V)) {
@@ -238,7 +243,8 @@
       if (CE->use_empty()) {
         CE->destroyConstant();
         Changed = true;
-      }
+      } else
+        append_range(Worklist, CE->users());
     } else if (Constant *C = dyn_cast<Constant>(U)) {
       if (isSafeToDestroyConstant(C)) {
         C->destroyConstant();


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