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Author SHA1 Message Date
Hans Wennborg 8eb336c14e Re-commit r269828 "X86: Avoid using _chkstk when lowering WIN_ALLOCA instructions" 
with an additional fix to make RegAllocFast ignore undef physreg uses. It would
previously get confused about the "push %eax" instruction's use of eax. That
method for adjusting the stack pointer is used in X86FrameLowering::emitSPUpdate
as well, but since that runs after register-allocation, we didn't run into the
RegAllocFast issue before.

llvm-svn: 269949
 2016-05-18 16:10:17 +00:00
Hans Wennborg 759af30109 Revert r269828 "X86: Avoid using _chkstk when lowering WIN_ALLOCA instructions" 
Seems to have broken the Windows ASan bot. Reverting while investigating.

llvm-svn: 269833
 2016-05-17 20:38:56 +00:00
Hans Wennborg c3fb51171e X86: Avoid using _chkstk when lowering WIN_ALLOCA instructions 
This patch moves the expansion of WIN_ALLOCA pseudo-instructions
into a separate pass that walks the CFG and lowers the instructions
based on a conservative estimate of the offset between the stack
pointer and the lowest accessed stack address.

The goal is to reduce binary size and run-time costs by removing
calls to _chkstk. While it doesn't fix all the code quality problems
with inalloca calls, it's an incremental improvement for PR27076.

Differential Revision: http://reviews.llvm.org/D20263

llvm-svn: 269828
 2016-05-17 20:13:29 +00:00