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Teach LTOModule to emit linker flags for dllexported symbols, plus interface cleanup.

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This change unifies how LTOModule and the backend obtain linker flags
for globals: via a new TargetLoweringObjectFile member function named
emitLinkerFlagsForGlobal. A new function LTOModule::getLinkerOpts() returns
the list of linker flags as a single concatenated string.

This change affects the C libLTO API: the function lto_module_get_*deplibs now
exposes an empty list, and lto_module_get_*linkeropts exposes a single element
which combines the contents of all observed flags. libLTO should never have
tried to parse the linker flags; it is the linker's job to do so. Because
linkers will need to be able to parse flags in regular object files, it
makes little sense for libLTO to have a redundant mechanism for doing so.

The new API is compatible with the old one. It is valid for a user to specify
multiple linker flags in a single pragma directive like this:

 #pragma comment(linker, "/defaultlib:foo /defaultlib:bar")

The previous implementation would not have exposed
either flag via lto_module_get_*deplibs (as the test in
TargetLoweringObjectFileCOFF::getDepLibFromLinkerOpt was case sensitive)
and would have exposed "/defaultlib:foo /defaultlib:bar" as a single flag via
lto_module_get_*linkeropts. This may have been a bug in the implementation,
but it does give us a chance to fix the interface.

Differential Revision: http://reviews.llvm.org/D10548

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241010 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne
2015-06-29 22:04:09 +00:00
parent b370959788
commit a6367d9136
11 changed files with 155 additions and 197 deletions
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11
include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
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@ -90,10 +90,6 @@ public:
~TargetLoweringObjectFileMachO() override {}
TargetLoweringObjectFileMachO();
/// Extract the dependent library name from a linker option string. Returns
/// StringRef() if the option does not specify a library.
StringRef getDepLibFromLinkerOpt(StringRef LinkerOption) const override;
/// Emit the module flags that specify the garbage collection information.
void emitModuleFlags(MCStreamer &Streamer,
ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
@ -150,10 +146,6 @@ public:
MCSection *getSectionForJumpTable(const Function &F, Mangler &Mang,
const TargetMachine &TM) const override;
/// Extract the dependent library name from a linker option string. Returns
/// StringRef() if the option does not specify a library.
StringRef getDepLibFromLinkerOpt(StringRef LinkerOption) const override;
/// Emit Obj-C garbage collection and linker options. Only linker option
/// emission is implemented for COFF.
void emitModuleFlags(MCStreamer &Streamer,
@ -164,6 +156,9 @@ public:
const MCSymbol *KeySym) const override;
MCSection *getStaticDtorSection(unsigned Priority,
const MCSymbol *KeySym) const override;
void emitLinkerFlagsForGlobal(raw_ostream &OS, const GlobalValue *GV,
const Mangler &Mang) const override;
};
} // end namespace llvm