bool runOnModule(Module &M) override;
private:
- SmallPtrSet<Constant *, 32> AliveGlobals;
+ SmallPtrSet<GlobalValue*, 32> AliveGlobals;
SmallPtrSet<Constant *, 8> SeenConstants;
- SmallPtrSet<GlobalVariable *, 8> DiscardableGlobalInitializers;
/// GlobalIsNeeded - mark the specific global value as needed, and
/// recursively mark anything that it uses as also needed.
void GlobalIsNeeded(GlobalValue *GV);
void MarkUsedGlobalsAsNeeded(Constant *C);
- /// \brief Checks if C is alive or is a ConstantExpr that refers to an alive
- /// value.
- bool ContainsUsedGlobal(Constant *C);
-
bool RemoveUnusedGlobalValue(GlobalValue &GV);
};
}
I->setAliasee(nullptr);
}
- // Look for available externally constants that we can turn into normal
- // externals by deleting their initalizers. This allows us to remove other
- // globals that are referenced by the initializer.
- if (!DiscardableGlobalInitializers.empty()) {
- for (GlobalVariable *GV : DiscardableGlobalInitializers) {
- if (!ContainsUsedGlobal(GV->getInitializer())) {
- GV->setInitializer(nullptr);
- GV->setLinkage(GlobalValue::ExternalLinkage);
- Changed = true;
- }
- }
- }
-
if (!DeadFunctions.empty()) {
// Now that all interferences have been dropped, delete the actual objects
// themselves.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G)) {
// If this is a global variable, we must make sure to add any global values
// referenced by the initializer to the alive set.
- if (GV->hasInitializer()) {
- if (GV->hasAvailableExternallyLinkage())
- DiscardableGlobalInitializers.insert(GV);
- else
- MarkUsedGlobalsAsNeeded(GV->getInitializer());
- }
+ if (GV->hasInitializer())
+ MarkUsedGlobalsAsNeeded(GV->getInitializer());
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(G)) {
// The target of a global alias is needed.
MarkUsedGlobalsAsNeeded(GA->getAliasee());
}
}
-bool GlobalDCE::ContainsUsedGlobal(Constant *C) {
- // C contains a used global If C is alive or we visited it while marking
- // values alive.
- if (AliveGlobals.count(C) || SeenConstants.count(C))
- return true;
-
- // Now check all operands of a ConstantExpr.
- for (User::op_iterator I = C->op_begin(), E = C->op_end(); I != E; ++I) {
- Constant *Op = dyn_cast<Constant>(*I);
- if (Op && ContainsUsedGlobal(Op))
- return true;
- }
- return false;
-}
-
// 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
-; RUN: opt < %s -globaldce -S | FileCheck %s
+; RUN: opt < %s -globaldce -S | not grep test_
; test_function should not be emitted to the .s file.
-; CHECK-NOT: @test_function
define available_externally i32 @test_function() {
ret i32 4
}
; test_global should not be emitted to the .s file.
-; CHECK-NOT: @test_global
@test_global = available_externally global i32 4
-; CHECK: @x = external constant void ()*
-@x = available_externally constant void()* @f
-; CHECK: @y = external constant i32
-@y = available_externally constant i32 ptrtoint (void()* @g to i32)
-; @h is still alive, so don't remove the initializer too eagerly.
-; CHECK: @z = available_externally constant i8 ptrtoint (void (i8)* @h to i8)
-@z = available_externally constant i8 ptrtoint (void(i8)* @h to i8)
-
-; CHECK-NOT: @f
-define linkonce_odr void @f() {
- ret void
-}
-
-; CHECK-NOT: @g
-define linkonce_odr void @g() {
- ret void
-}
-
-; CHECK: define linkonce_odr void @h
-define linkonce_odr void @h(i8) {
- ret void
-}
-
-define i32 @main() {
- %f = load void()** @x
- call void %f()
- %g = load i32* @y
- %h = load i8* @z
- call void @h(i8 %h)
- ret i32 %g
-}