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ZJIT: Fix SP alignment on JIT entry for x86_64

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This commit is contained in:
Takashi Kokubun 2025-07-15 13:24:37 -07:00
parent 4eb0a6cd4d
commit 2250a66aa8
2 changed files with 31 additions and 12 deletions
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23
zjit/src/codegen.rs
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@ -156,10 +156,6 @@ fn gen_entry(cb: &mut CodeBlock, iseq: IseqPtr, function: &Function, function_pt
// Restore registers for CFP, EC, and SP after use
asm_comment!(asm, "exit to the interpreter");
// On x86_64, maintain 16-byte stack alignment
if cfg!(target_arch = "x86_64") {
asm.cpop_into(SP);
}
asm.cpop_into(SP);
asm.cpop_into(EC);
asm.cpop_into(CFP);
@ -511,10 +507,6 @@ fn gen_entry_prologue(asm: &mut Assembler, iseq: IseqPtr) {
asm.cpush(CFP);
asm.cpush(EC);
asm.cpush(SP);
// On x86_64, maintain 16-byte stack alignment
if cfg!(target_arch = "x86_64") {
asm.cpush(SP);
}
// EC and CFP are passed as arguments
asm.mov(EC, C_ARG_OPNDS[0]);
@ -1157,12 +1149,19 @@ fn max_num_params(function: &Function) -> usize {
/// the function needs to allocate on the stack for the stack frame.
fn aligned_stack_bytes(num_slots: usize) -> usize {
// Both x86_64 and arm64 require the stack to be aligned to 16 bytes.
// Since SIZEOF_VALUE is 8 bytes, we need to round up the size to the nearest even number.
let num_slots = if num_slots % 2 == 0 {
num_slots
} else {
let num_slots = if cfg!(target_arch = "x86_64") && num_slots % 2 == 0 {
// On x86_64, since the call instruction bumps the stack pointer by 8 bytes on entry,
// we need to round up `num_slots` to an odd number.
num_slots + 1
} else if cfg!(target_arch = "aarch64") && num_slots % 2 == 1 {
// On arm64, the stack pointer is always aligned to 16 bytes, so we need to round up
// `num_slots`` to an even number.
num_slots + 1
} else {
num_slots
};
const _: () = assert!(SIZEOF_VALUE == 8, "aligned_stack_bytes() assumes SIZEOF_VALUE == 8");
num_slots * SIZEOF_VALUE
}