[llvm] 5798be8 - Revert D103717 "[InstrProfiling] Make __profd_ unconditionally private for ELF"

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2021-06-17T23:38:17-07:00
New Revision: 5798be84580be233e4cf34c08ceec8f79e80502e

URL: https://github.com/llvm/llvm-project/commit/5798be84580be233e4cf34c08ceec8f79e80502e
DIFF: https://github.com/llvm/llvm-project/commit/5798be84580be233e4cf34c08ceec8f79e80502e.diff

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

This reverts commit 76d0747e0807307780ba84cbd7e5c80b20c26bd7.

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
```

Added: 
    

Modified: 
    llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
    llvm/test/Transforms/PGOProfile/indirect_call_profile.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
index 6b5ca896e358e..4a5511d375fd7 100644
--- a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -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;
   }

diff  --git a/llvm/test/Transforms/PGOProfile/indirect_call_profile.ll b/llvm/test/Transforms/PGOProfile/indirect_call_profile.ll
index 0fa6c5258b55e..a3c05e5b47015 100644
--- a/llvm/test/Transforms/PGOProfile/indirect_call_profile.ll
+++ b/llvm/test/Transforms/PGOProfile/indirect_call_profile.ll
@@ -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