[llvm] r212550 - Revert "GlobalDCE: Delete available_externally initializers if it allows removing the value the initializer is referring to."
Pete Cooper
peter_cooper at apple.com
Tue Jul 8 13:11:00 PDT 2014
Thanks David.
I’m still getting used to mixing git and svn so the script here is very much appreciated.
Pete
> On Jul 8, 2014, at 6:22 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
> On Tue, Jul 8, 2014 at 10:06 AM, Pete Cooper <peter_cooper at apple.com> wrote:
>> Author: pete
>> Date: Tue Jul 8 12:06:03 2014
>> New Revision: 212550
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=212550&view=rev
>> Log:
>> Revert "GlobalDCE: Delete available_externally initializers if it allows removing the value the initializer is referring to."
>>
>> This reverts commit 5b55a47e94e28fbb56d0cd5d72c3db9105c15b4c.
>
> There's a neat script (llvm/utils/git-svn/git-svnrevert) that will
> revert a given git commit specified by a hash, but create a commit
> message that specifies the SVN revision, so that it's useful to
> someone reading the commit message (especially later on when
> spelunking through history).
>
> - David
>
>>
>> A test case was found to crash after this was applied. I'll file a bug to track fixing this with the test case needed.
>>
>> Modified:
>> llvm/trunk/lib/Transforms/IPO/GlobalDCE.cpp
>> llvm/trunk/test/Transforms/GlobalDCE/externally_available.ll
>>
>> Modified: llvm/trunk/lib/Transforms/IPO/GlobalDCE.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/GlobalDCE.cpp?rev=212550&r1=212549&r2=212550&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/IPO/GlobalDCE.cpp (original)
>> +++ llvm/trunk/lib/Transforms/IPO/GlobalDCE.cpp Tue Jul 8 12:06:03 2014
>> @@ -44,19 +44,14 @@ namespace {
>> 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);
>> };
>> }
>> @@ -167,19 +162,6 @@ bool GlobalDCE::runOnModule(Module &M) {
>> 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.
>> @@ -227,12 +209,8 @@ void GlobalDCE::GlobalIsNeeded(GlobalVal
>> 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());
>> @@ -270,21 +248,6 @@ void GlobalDCE::MarkUsedGlobalsAsNeeded(
>> }
>> }
>>
>> -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
>>
>> Modified: llvm/trunk/test/Transforms/GlobalDCE/externally_available.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GlobalDCE/externally_available.ll?rev=212550&r1=212549&r2=212550&view=diff
>> ==============================================================================
>> --- llvm/trunk/test/Transforms/GlobalDCE/externally_available.ll (original)
>> +++ llvm/trunk/test/Transforms/GlobalDCE/externally_available.ll Tue Jul 8 12:06:03 2014
>> @@ -1,43 +1,10 @@
>> -; 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 ()*
>> - at x = available_externally constant void()* @f
>> -; CHECK: @y = external constant i32
>> - at 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)
>> - at 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
>> -}
>>
>>
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