[llvm] 76d0747 - [InstrProfiling] Make __profd_ unconditionally private for ELF

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2021-06-17T14:16:54-07:00
New Revision: 76d0747e0807307780ba84cbd7e5c80b20c26bd7

URL: https://github.com/llvm/llvm-project/commit/76d0747e0807307780ba84cbd7e5c80b20c26bd7
DIFF: https://github.com/llvm/llvm-project/commit/76d0747e0807307780ba84cbd7e5c80b20c26bd7.diff

LOG: [InstrProfiling] Make __profd_ unconditionally private for ELF

For ELF, since all counters/data are in a section group (either `comdat any` or
`comdat noduplicates`), and the signature for `comdat any` is `__profc_`, the
D1003372 optimization prerequisite (linker GC cannot discard data variables
while the text section is retained) is always satisified, we can make __profd_
unconditionally private.

Reviewed By: davidxl, rnk

Differential Revision: https://reviews.llvm.org/D103717

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 4a5511d375fd7..6b5ca896e358e 100644
--- a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -929,10 +929,12 @@ InstrProfiling::getOrCreateRegionCounters(InstrProfIncrementInst *Inc) {
 #define INSTR_PROF_DATA(Type, LLVMType, Name, Init) Init,
 #include "llvm/ProfileData/InstrProfData.inc"
   };
-  // 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()) {
+  // 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())) {
     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 a3c05e5b47015..0fa6c5258b55e 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]+]] = linkonce_odr{{.*}}@__profc_foo3.[[FOO3_HASH]]
+; LOWER: @__profd_foo3.[[FOO3_HASH:[0-9]+]] = private {{.*}} @__profc_foo3.[[FOO3_HASH]]
 ; Function Attrs: nounwind uwtable
 define linkonce_odr i32 @foo3()  comdat  {
   ret i32 1