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author | Anton Bikineev <bikineev@chromium.org> | 2023-02-06 13:16:08 +0100 |
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committer | Anton Bikineev <bikineev@chromium.org> | 2023-02-09 10:59:16 +0100 |
commit | 10629bb96aebfefaadfb0069bc7e276b868fcef9 (patch) | |
tree | ae3f374ff2df33a8e1da2bb8db3b3524f628b131 /llvm/unittests/TextAPI | |
parent | 2929683eef27e6b3ac95325d955cd39bc2e416c0 (diff) | |
download | llvm-10629bb96aebfefaadfb0069bc7e276b868fcef9.zip llvm-10629bb96aebfefaadfb0069bc7e276b868fcef9.tar.gz llvm-10629bb96aebfefaadfb0069bc7e276b868fcef9.tar.bz2 |
Reland "[X86][ABI] Don't preserve return regs for preserve_all/preserve_most CCs""
The original change mistakenly excluded parameter registers from the
list of callee-saved-registers. This reland fixes it - it only excludes
the return registers for preserve_all/preserve_most CCs.
Original description:
> Currently both calling conventions preserve registers that are used to
> store a return value. This causes the returned value to be lost:
>
> define i32 @bar() {
> %1 = call preserve_mostcc i32 @foo()
> ret i32 %1
> }
>
> define preserve_mostcc i32 @foo() {
> ret i32 2
> ; preserve_mostcc will restore %rax,
> ; whatever it was before the call.
> }
>
> This contradicts the current documentation (preserve_allcc "behaves
> identical to the `C` calling conventions on how arguments and return
> values are passed") and also breaks [[clang::preserve_most]].
>
> This change makes CSRs be preserved iff they are not used to store a
> return value (e.g. %rax for scalars, {%rax:%rdx} for __int128, %xmm0
> for double). For void functions no additional registers are
> preserved, i.e. the behaviour is backward compatible with existing
> code.
Differential Revision: https://reviews.llvm.org/D143425
Diffstat (limited to 'llvm/unittests/TextAPI')
0 files changed, 0 insertions, 0 deletions