[PATCH] D12458: [clang] add __builtin_unpredictable and convert to metadata

[Sanjay Patel via cfe-commits]

spatel created this revision.
spatel added reviewers: hfinkel, kbsmith1, kparzysz, reames, silvas.
spatel added a subscriber: cfe-commits.
spatel added a dependency: D12341: add unpredictable metadata type for control flow.

This patch depends on D12341 ('unpredictable' metadata type for LLVM). 

For now, I am ignoring the horrible thought that this builtin might take an extra parameter to distinguish different hardware. :)

The goal is to make LLVM generate different code for these functions for a target that has cheap branches (see PR23827 for more details):

   int foo();
   int normal(int x, int y, int z) {
      if (x != 0 && y != 0) return foo();
      return 1;
   }
   
   int crazy(int x, int y) {
      if (__builtin_unpredictable(x != 0 && y != 0)) return foo();
      return 1;
   }



http://reviews.llvm.org/D12458

Files:
  docs/LanguageExtensions.rst
  include/clang/Basic/Builtins.def
  lib/CodeGen/CGBuiltin.cpp
  lib/CodeGen/CodeGenFunction.cpp
  lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
  test/CodeGen/builtin-unpredictable.c

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D12458.33491.patch
Type: text/x-patch
Size: 6263 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20150828/031c5a91/attachment.bin>