[PATCH] D117034: [GlobalOpt] Support "stored once" optimization for different types

[Nikita Popov via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rGf3e87176e1c5: [GlobalOpt] Support "stored once" optimization for different types (authored by nikic).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D117034/new/

https://reviews.llvm.org/D117034

Files:
  llvm/lib/Transforms/IPO/GlobalOpt.cpp
  llvm/test/Transforms/GlobalOpt/stored-once-different-type.ll
  llvm/test/Transforms/GlobalOpt/stored-once-value-type.ll


Index: llvm/test/Transforms/GlobalOpt/stored-once-value-type.ll
===================================================================
--- llvm/test/Transforms/GlobalOpt/stored-once-value-type.ll
+++ llvm/test/Transforms/GlobalOpt/stored-once-value-type.ll
@@ -8,13 +8,8 @@
 
 @0 = internal global %T* null
 
-;.
-; CHECK: @[[_BODY:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr global [[T:%.*]] undef
-;.
 define void @a() {
 ; CHECK-LABEL: @a(
-; CHECK-NEXT:    store i32* null, i32** getelementptr inbounds ([[T:%.*]], %T* @.body, i64 0, i32 0), align 8
-; CHECK-NEXT:    [[TMP1:%.*]] = load atomic i64, i64* bitcast (%T* @.body to i64*) acquire, align 8
 ; CHECK-NEXT:    ret void
 ;
   %1 = tail call i8* @_Znwm(i64 8)
Index: llvm/test/Transforms/GlobalOpt/stored-once-different-type.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/GlobalOpt/stored-once-different-type.ll
@@ -0,0 +1,40 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals
+; RUN: opt -S -globalopt < %s | FileCheck %s
+
+ at g = internal global [4 x i8] undef
+
+;.
+; CHECK: @[[G:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr constant i32 42
+;.
+define void @store() {
+; CHECK-LABEL: @store(
+; CHECK-NEXT:    ret void
+;
+  store i32 42, i32* bitcast ([4 x i8]* @g to i32*)
+  ret void
+}
+
+define i32 @load1() {
+; CHECK-LABEL: @load1(
+; CHECK-NEXT:    ret i32 42
+;
+  %v = load i32, i32* bitcast ([4 x i8]* @g to i32*)
+  ret i32 %v
+}
+
+define i16 @load2() {
+; CHECK-LABEL: @load2(
+; CHECK-NEXT:    ret i16 42
+;
+  %v = load i16, i16* bitcast ([4 x i8]* @g to i16*)
+  ret i16 %v
+}
+
+define [4 x i8] @load3() {
+; CHECK-LABEL: @load3(
+; CHECK-NEXT:    [[V:%.*]] = load [4 x i8], [4 x i8]* bitcast (i32* @g to [4 x i8]*), align 1
+; CHECK-NEXT:    ret [4 x i8] [[V]]
+;
+  %v = load [4 x i8], [4 x i8]* @g
+  ret [4 x i8] %v
+}
Index: llvm/lib/Transforms/IPO/GlobalOpt.cpp
===================================================================
--- llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -1672,11 +1672,25 @@
     // This is restricted to address spaces that allow globals to have
     // initializers. NVPTX, for example, does not support initializers for
     // shared memory (AS 3).
-    if (SOVConstant && SOVConstant->getType() == GV->getValueType() &&
-        isa<UndefValue>(GV->getInitializer()) &&
+    if (SOVConstant && isa<UndefValue>(GV->getInitializer()) &&
+        DL.getTypeAllocSize(SOVConstant->getType()) ==
+            DL.getTypeAllocSize(GV->getValueType()) &&
         CanHaveNonUndefGlobalInitializer) {
-      // Change the initial value here.
-      GV->setInitializer(SOVConstant);
+      if (SOVConstant->getType() == GV->getValueType()) {
+        // Change the initializer in place.
+        GV->setInitializer(SOVConstant);
+      } else {
+        // Create a new global with adjusted type.
+        auto *NGV = new GlobalVariable(
+            *GV->getParent(), SOVConstant->getType(), GV->isConstant(),
+            GV->getLinkage(), SOVConstant, "", GV, GV->getThreadLocalMode(),
+            GV->getAddressSpace());
+        NGV->takeName(GV);
+        NGV->copyAttributesFrom(GV);
+        GV->replaceAllUsesWith(ConstantExpr::getBitCast(NGV, GV->getType()));
+        GV->eraseFromParent();
+        GV = NGV;
+      }
 
       // Clean up any obviously simplifiable users now.
       CleanupConstantGlobalUsers(GV, DL);


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