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[MergeFunc] Erase unused duplicate functions if they are discardable

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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

llvm-svn: 350939
This commit is contained in:
Vedant Kumar 2019-01-11 17:56:35 +00:00
parent fae3f2471d
commit de4374ce0b
2 changed files with 14 additions and 2 deletions
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2
lib/Transforms/IPO/MergeFunctions.cpp
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@ -845,7 +845,7 @@ void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
// 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;

14
test/Transforms/MergeFunc/linkonce_odr.ll
View File

@ -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, i32 %y) {
%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.
@take_addr_of_funB = global i8* bitcast (i32 (i32, i32)* @funB to i8*)