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Use RCX instead of R10 as temp register in sysv call location.

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This commit is contained in:
losfair 2020-04-30 00:04:44 +08:00
parent d23a3f3d1c
commit b2ecf8a06c
1 changed files with 11 additions and 5 deletions
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16
lib/singlepass-backend/src/codegen_x64.rs
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@ -1942,7 +1942,10 @@ impl X64FunctionCode {
/// Emits a System V call sequence.
///
/// This function must not use RAX before `cb` is called.
/// This function will not use RAX before `cb` is called.
///
/// The caller MUST NOT hold any temporary registers allocated by `acquire_temp_gpr` when calling
/// this function.
fn emit_call_sysv<I: Iterator<Item = Location>, F: FnOnce(&mut Assembler)>(
a: &mut Assembler,
m: &mut Machine,
@ -2063,14 +2066,17 @@ impl X64FunctionCode {
// Dummy value slot to be filled with `mov`.
a.emit_push(Size::S64, Location::GPR(GPR::RAX));
// Use R10 as the temporary register here, since it is callee-saved and not
// used by the callback `cb`.
a.emit_mov(Size::S64, *param, Location::GPR(GPR::R10));
// Use RCX as the temporary register here, since:
// - It is a temporary register that is not used for any persistent value.
// - This register as an argument location is only written to after `sort_call_movs`.'
m.reserve_unused_temp_gpr(GPR::RCX);
a.emit_mov(Size::S64, *param, Location::GPR(GPR::RCX));
a.emit_mov(
Size::S64,
Location::GPR(GPR::R10),
Location::GPR(GPR::RCX),
Location::Memory(GPR::RSP, 0),
);
m.release_temp_gpr(GPR::RCX);
}
Location::XMM(_) => {
// Dummy value slot to be filled with `mov`.