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COFF: Do not assign linker-weak symbols to selectany comdat sections.

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It is mandatory to specify a comdat in order to receive comdat semantics
for a symbol. We were previously getting this wrong in -function-sections
mode; linker-weak symbols were being emitted in a selectany comdat. This
change causes such symbols to use a noduplicates comdat instead, fixing
the inconsistency.

Also correct an inaccuracy in the docs.

Differential Revision: http://reviews.llvm.org/D10828

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241103 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne 2015-06-30 19:10:31 +00:00
parent 528f9649c8
commit fd8c98591d
3 changed files with 14 additions and 5 deletions
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8
docs/LangRef.rst
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@ -823,9 +823,11 @@ with the same name. This is necessary because both globals belong to different
COMDAT groups and COMDATs, at the object file level, are represented by
sections.
Note that certain IR constructs like global variables and functions may create
COMDATs in the object file in addition to any which are specified using COMDAT
IR. This arises, for example, when a global variable has linkonce_odr linkage.
Note that certain IR constructs like global variables and functions may
create COMDATs in the object file in addition to any which are specified using
COMDAT IR. This arises when the code generator is configured to emit globals
in individual sections (e.g. when `-data-sections` or `-function-sections`
is supplied to `llc`).
.. _namedmetadatastructure:

2
lib/CodeGen/TargetLoweringObjectFileImpl.cpp
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@ -840,8 +840,6 @@ static int getSelectionForCOFF(const GlobalValue *GV) {
} else {
return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
}
} else if (GV->isWeakForLinker()) {
return COFF::IMAGE_COMDAT_SELECT_ANY;
}
return 0;
}

9
test/CodeGen/X86/coff-weak.ll Normal file
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@ -0,0 +1,9 @@
; RUN: llc -function-sections -o - %s | FileCheck %s
target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-windows-msvc"
; CHECK: .section{{.*}}one_only
define linkonce_odr void @foo() {
ret void
}