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Author SHA1 Message Date
Peter Collingbourne 00dc23f26e Revert r337638, "ELF: Make sections with KeepUnique bit eligible for ICF." 
The gold behaviour with regard to --keep-unique is arguably a bug.
I also noticed a bug in my patch, which is that we mislink the
following program with --icf=safe by merging f3 and f4:

void f1() {}
void f2() {}

__attribute__((weak)) void* f3() { return f1; }
__attribute__((weak)) void* f4() { return f2; }

int main() {
  printf("%p %p\n", f3(), f4());
}

llvm-svn: 337729
 2018-07-23 19:36:55 +00:00
Peter Collingbourne 37f25a24bb ELF: Make sections with KeepUnique bit eligible for ICF. 
The only restriction is that we cannot merge more than one KeepUnique
section together. This matches gold's behaviour and reduces code size
when using --icf=safe.

Differential Revision: https://reviews.llvm.org/D49622

llvm-svn: 337638
 2018-07-21 00:17:11 +00:00
Peter Smith dbef8cc67c [ELF] Implement --keep-unique option 
The --keep-unique <symbol> option is taken from gold. The intention is that
<symbol> will be prevented from being folded by ICF. Although not
specifically mentioned in the documentation <symbol> only matches
global symbols, with a warning if the symbol is not found.

The implementation finds the Section defining <symbol> and removes it from
the set of sections considered for ICF.

Differential Revision: https://reviews.llvm.org/D46755

llvm-svn: 332332
 2018-05-15 08:57:21 +00:00