AArch64: Omit callframe setup/destroy when not necessary
Do not create CALLSEQ_START/CALLSEQ_END when there is no callframe to
setup and the callframe size is 0.
- Fixes an invalid callframe nesting for byval arguments, which would
look like this before this patch (as in `big-byval.ll`):
...
ADJCALLSTACKDOWN 32768, 0, ... # Setup for extfunc
...
ADJCALLSTACKDOWN 0, 0, ... # setup for memcpy
...
BL &memcpy ...
ADJCALLSTACKUP 0, 0, ... # destroy for memcpy
...
BL &extfunc
ADJCALLSTACKUP 32768, 0, ... # destroy for extfunc
- Saves us two instructions in the common case of zero-sized stackframes.
- Remove an unnecessary scheduling barrier (hence the small unittest
changes).
Differential Revision: https://reviews.llvm.org/D42006
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@322917 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed