steven_wu added a comment.
Attach a new patch with the comments
================
Comment at: lib/CodeGen/BackendUtil.cpp:799-831
@@ +798,35 @@
+ // Embed the bitcode for the llvm module.
+ std::string Data;
+ ArrayRef<uint8_t> ModuleData;
+ Triple T(M->getTargetTriple());
+ if (CGOpts.getEmbedBitcode() != CodeGenOptions::Embed_Marker) {
+ if (!isBitcode((const unsigned char *)Buf.getBufferStart(),
+ (const unsigned char *)Buf.getBufferEnd())) {
+ // If the input is LLVM Assembly, bitcode is produced by serializing
+ // the module. Use-lists order need to be perserved in this case.
+ llvm::raw_string_ostream OS(Data);
+ llvm::WriteBitcodeToFile(M, OS, /* ShouldPreserveUseListOrder */ true);
+ ModuleData =
+ ArrayRef<uint8_t>((const uint8_t *)OS.str().data(), OS.str().size());
+ } else
+ // If the input is LLVM bitcode, write the input byte stream directly.
+ ModuleData = ArrayRef<uint8_t>((const uint8_t *)Buf.getBufferStart(),
+ Buf.getBufferSize());
+ }
+ llvm::Constant *ModuleConstant =
+ llvm::ConstantDataArray::get(M->getContext(), ModuleData);
+ // Use Appending linkage so it doesn't get optimized out.
+ llvm::GlobalVariable *GV = new llvm::GlobalVariable(
+ *M, ModuleConstant->getType(), true, llvm::GlobalValue::AppendingLinkage,
+ ModuleConstant);
+ GV->setSection(getSectionNameForBitcode(T));
+ if (llvm::GlobalVariable *Old =
+ M->getGlobalVariable("llvm.embedded.module")) {
+ assert(Old->use_empty() && "llvm.embedded.module must have no uses");
+ GV->takeName(Old);
+ Old->eraseFromParent();
+ } else {
+ GV->setName("llvm.embedded.module");
+ }
+
+ // Return if only bitcode needs to be embedded.
----------------
rsmith wrote:
> I see, the "marker" is an empty `llvm.embedded.module` constant. Please add a
> comment to that effect; that's not obvious.
Sure.
================
Comment at: lib/Driver/Tools.cpp:5710-5714
@@ -5709,4 +5709,7 @@
// by the frontend.
- if (C.getDriver().isSaveTempsEnabled() && isa<CompileJobAction>(JA))
+ // When -fembed-bitcode is enabled, optimized bitcode is emitted because it
+ // has slightly different breakdown between stages.
+ if (C.getDriver().isSaveTempsEnabled() &&
+ !C.getDriver().embedBitcodeEnabled() && isa<CompileJobAction>(JA))
CmdArgs.push_back("-disable-llvm-passes");
----------------
rsmith wrote:
> This means that `-fembed-bitcode -save-temps` will save different
> intermediate IR than `-save-temps` alone; that seems wrong. I would expect
> that process to save the unoptimized IR but embed the optimized IR. Getting
> that right will probably require adding another action to the pipeline for
> that combination of flags.
That is exactly the case. I will add a FIXME here.
http://reviews.llvm.org/D17392
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