[PATCH] D42602: [PowerPC] Reduce stack frame for fastcc functions by only allocating parameter save area when needed

[Lei Huang via Phabricator via llvm-commits]

lei created this revision.
lei added reviewers: power-llvm-team, echristo, hfinkel.
Herald added subscribers: kbarton, nemanjai.

Current implementation always allocates the parameter save area conservatively for fastcc functions.  There is no reason to allocate the parameter save area for fastcc function if all the parameters can be passed via registers.

This patch reduces the stack frame usage for:

- stage2 bootstrap by 4%
- gcc by 7%
- perlbench and povray by 2%

SPEC2006 performance run shows no performance changes.


https://reviews.llvm.org/D42602

Files:
  lib/Target/PowerPC/PPCISelLowering.cpp
  test/CodeGen/PowerPC/fastcc_stacksize.ll

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