[llvm] r350939 - [MergeFunc] Erase unused duplicate functions if they are discardable

[Vedant Kumar via llvm-commits]

Fixed in cfe/r350952, sorry for the churn.

vedant

> On Jan 11, 2019, at 10:50 AM, Vedant Kumar <vsk at apple.com> wrote:
> 
> This caused buildbot failures in clang/test/CodeGenCXX/merge-functions.cpp. I should have a fix momentarily.
> 
> vedant
> 
>> On Jan 11, 2019, at 9:56 AM, Vedant Kumar via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>> 
>> Author: vedantk
>> Date: Fri Jan 11 09:56:35 2019
>> New Revision: 350939
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=350939&view=rev
>> Log:
>> [MergeFunc] Erase unused duplicate functions if they are discardable
>> 
>> MergeFunc only deletes unused duplicate functions if they have local
>> linkage, but it should be safe to relax this to any "discardable if
>> unused" linkage type.
>> 
>> Differential Revision: https://reviews.llvm.org/D56574
>> 
>> Modified:
>>   llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp
>>   llvm/trunk/test/Transforms/MergeFunc/linkonce_odr.ll
>> 
>> Modified: llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp?rev=350939&r1=350938&r2=350939&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp (original)
>> +++ llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp Fri Jan 11 09:56:35 2019
>> @@ -845,7 +845,7 @@ void MergeFunctions::mergeTwoFunctions(F
>>    // If G was internal then we may have replaced all uses of G with F. If so,
>>    // stop here and delete G. There's no need for a thunk. (See note on
>>    // MergeFunctionsPDI above).
>> -    if (G->hasLocalLinkage() && G->use_empty() && !MergeFunctionsPDI) {
>> +    if (G->isDiscardableIfUnused() && G->use_empty() && !MergeFunctionsPDI) {
>>      G->eraseFromParent();
>>      ++NumFunctionsMerged;
>>      return;
>> 
>> Modified: llvm/trunk/test/Transforms/MergeFunc/linkonce_odr.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/MergeFunc/linkonce_odr.ll?rev=350939&r1=350938&r2=350939&view=diff
>> ==============================================================================
>> --- llvm/trunk/test/Transforms/MergeFunc/linkonce_odr.ll (original)
>> +++ llvm/trunk/test/Transforms/MergeFunc/linkonce_odr.ll Fri Jan 11 09:56:35 2019
>> @@ -1,4 +1,4 @@
>> -; RUN: opt -S -mergefunc < %s | FileCheck %s
>> +; RUN: opt -S -mergefunc < %s | FileCheck %s -implicit-check-not=funC
>> 
>> ; Replacments should be totally ordered on the function name.
>> ; If we don't do this we  can end up with one module defining a thunk for @funA
>> @@ -15,6 +15,13 @@
>> ; CHECK-NEXT:    tail call i32 @funA(i32 %0, i32 %1)
>> ; CHECK-NEXT:    ret
>> 
>> +define linkonce_odr i32 @funC(i32 %x, i32 %y) {
>> +  %sum = add i32 %x, %y
>> +  %sum2 = add i32 %x, %sum
>> +  %sum3 = add i32 %x, %sum2
>> +  ret i32 %sum3
>> +}
>> +
>> define linkonce_odr i32 @funB(i32 %x, i32 %y) {
>>  %sum = add i32 %x, %y
>>  %sum2 = add i32 %x, %sum
>> @@ -28,3 +35,8 @@ define linkonce_odr i32 @funA(i32 %x, i3
>>  %sum3 = add i32 %x, %sum2
>>  ret i32 %sum3
>> }
>> +
>> +; This creates a use of @funB, preventing -mergefunc from deleting it.
>> +; @funC, however, can safely be deleted as it has no uses, and is discardable
>> +; if unused.
>> + at take_addr_of_funB = global i8* bitcast (i32 (i32, i32)* @funB to i8*)
>> 
>> 
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