ThinLTO Minimized Bitcode File Size Reduction

ThinLTO Minimized Bitcode File Size Reduction

Summary: Currently the ThinLTO minimized bitcode file only strip the debug info, but there is still a lot of information in the minimized bit code file that will be not used for thin linker. In this patch, most of the extra information is striped to reduce the minimized bitcode file. Now only ModuleVersion, ModuleInfo, ModuleGlobalValueSummary, ModuleHash, Symtab and Strtab are left. Now the minimized bitcode file size is reduced to 15%-30% of the debug info stripped bitcode file size.

Reviewers: danielcdh, tejohnson, pcc

Reviewed By: pcc

Subscribers: mehdi_amini, aprantl, inglorion, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D35334

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@308760 91177308-0d34-0410-b5e6-96231b3b80d8