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Revert D103717 "[InstrProfiling] Make __profd_ unconditionally private for ELF" 

This reverts commit 76d0747e08.

If a group has `__llvm_prf_vals` due to static value profiler counters
(`NS!=0`), we cannot make `__llvm_prf_data` private, because a prevailing text
section may reference `__llvm_prf_data` and will cause a `relocation refers to a
discarded section` linker error.

Note: while a `__profc_` group is non-prevailing, it may be referenced by a
prevailing text section due to inlining.

```
group section [   66] `.group' [__profc__ZN5clang20EmitClangDeclContextERN4llvm12RecordKeeperERNS0_11raw_ostreamE] contains 4 sections:
   [Index]    Name
   [   67]   __llvm_prf_cnts
   [   68]   __llvm_prf_vals
   [   69]   __llvm_prf_data
   [   70]   .rela__llvm_prf_data
```
This commit is contained in:
Fangrui Song 2021-06-17 23:38:17 -07:00
parent 30c9d68ad9
commit 5798be8458
2 changed files with 5 additions and 7 deletions
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10
llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
View File

@ -929,12 +929,10 @@ InstrProfiling::getOrCreateRegionCounters(InstrProfIncrementInst *Inc) {
#define INSTR_PROF_DATA(Type, LLVMType, Name, Init) Init,
#include "llvm/ProfileData/InstrProfData.inc"
};
// If linker GC cannot discard data variables while the text section is
// retained, data variables can be private. This optimization applies on ELF.
// On COFF, when DataReferencedByCode is false, __profd_ is never a comdat
// leader, this is applicable as well.
if (TT.isOSBinFormatELF() ||
(!DataReferencedByCode && TT.isOSBinFormatCOFF())) {
// If code never references data variables (the symbol is unneeded), and
// linker GC cannot discard data variables while the text section is retained,
// data variables can be private. This optimization applies on COFF and ELF.
if (!DataReferencedByCode && !TT.isOSBinFormatMachO()) {
Linkage = GlobalValue::PrivateLinkage;
Visibility = GlobalValue::DefaultVisibility;
}

2
llvm/test/Transforms/PGOProfile/indirect_call_profile.ll
View File

@ -54,7 +54,7 @@ bb11: ; preds = %bb2
}
; Test that comdat function's address is recorded.
; LOWER: @__profd_foo3.[[FOO3_HASH:[0-9]+]] = private {{.*}} @__profc_foo3.[[FOO3_HASH]]
; LOWER: @__profd_foo3.[[FOO3_HASH:[0-9]+]] = linkonce_odr{{.*}}@__profc_foo3.[[FOO3_HASH]]
; Function Attrs: nounwind uwtable
define linkonce_odr i32 @foo3() comdat {
ret i32 1