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Implement the isSafeToDiscardIfUnused predicate and use it in globalopt and
globaldce. Globaldce was already removing linkonce globals, but globalopt was not. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158476 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -164,6 +164,12 @@ public:
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return Linkage == CommonLinkage;
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}
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/// isDiscardableIfUnused - Whether the definition of this global may be
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/// discarded if it is not used in its compilation unit.
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static bool isDiscardableIfUnused(LinkageTypes Linkage) {
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return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage);
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}
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/// mayBeOverridden - Whether the definition of this global may be replaced
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/// by something non-equivalent at link time. For example, if a function has
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/// weak linkage then the code defining it may be replaced by different code.
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@ -221,6 +227,10 @@ public:
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void setLinkage(LinkageTypes LT) { Linkage = LT; }
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LinkageTypes getLinkage() const { return Linkage; }
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bool isDiscardableIfUnused() const {
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return isDiscardableIfUnused(Linkage);
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}
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bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
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bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
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@ -65,7 +65,7 @@ bool GlobalDCE::runOnModule(Module &M) {
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for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
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Changed |= RemoveUnusedGlobalValue(*I);
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// Functions with external linkage are needed if they have a body
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if (!I->hasLocalLinkage() && !I->hasLinkOnceLinkage() &&
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if (!I->isDiscardableIfUnused() &&
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!I->isDeclaration() && !I->hasAvailableExternallyLinkage())
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GlobalIsNeeded(I);
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}
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@ -75,7 +75,7 @@ bool GlobalDCE::runOnModule(Module &M) {
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Changed |= RemoveUnusedGlobalValue(*I);
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// Externally visible & appending globals are needed, if they have an
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// initializer.
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if (!I->hasLocalLinkage() && !I->hasLinkOnceLinkage() &&
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if (!I->isDiscardableIfUnused() &&
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!I->isDeclaration() && !I->hasAvailableExternallyLinkage())
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GlobalIsNeeded(I);
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}
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@ -84,7 +84,7 @@ bool GlobalDCE::runOnModule(Module &M) {
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I != E; ++I) {
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Changed |= RemoveUnusedGlobalValue(*I);
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// Externally visible aliases are needed.
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if (!I->hasLocalLinkage() && !I->hasLinkOnceLinkage())
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if (!I->isDiscardableIfUnused())
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GlobalIsNeeded(I);
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}
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@ -1716,7 +1716,7 @@ static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
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/// possible. If we make a change, return true.
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bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
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Module::global_iterator &GVI) {
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if (!GV->hasLocalLinkage())
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if (!GV->isDiscardableIfUnused())
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return false;
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// Do more involved optimizations if the global is internal.
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@ -1,9 +1,25 @@
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; RUN: opt < %s -globalopt -S | not grep internal
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; RUN: opt < %s -globalopt -S | FileCheck %s
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@G = internal global i32 123 ; <i32*> [#uses=1]
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@G1 = internal global i32 123 ; <i32*> [#uses=1]
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define void @foo() {
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store i32 1, i32* @G
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; CHECK-NOT: @G1
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; CHECK: @G2
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; CHECK-NOT: @G3
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define void @foo1() {
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; CHECK: define void @foo
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; CHECK-NEXT: ret
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store i32 1, i32* @G1
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ret void
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}
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@G2 = linkonce_odr constant i32 42
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define void @foo2() {
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; CHECK: define void @foo2
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; CHECK-NEXT: store
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store i32 1, i32* @G2
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ret void
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}
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@G3 = linkonce_odr constant i32 42
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