From ba4d961b2065beb88e84f1a627b270149958ac7d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20Balv=C3=ADn?= <opensource@petrbalvin.org>
Date: Fri, 28 Aug 2026 22:11:24 +0200
Subject: [PATCH] fix(asm): ADDQ imm8 frame adjust for 128-255 byte frames

---
 asm/assemble.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/asm/assemble.go b/asm/assemble.go
index 1be3793..f0f2648 100644
--- a/asm/assemble.go
+++ b/asm/assemble.go
@@ -261,6 +261,11 @@ func subSP(size int) []byte { // SUBQ $size, SP
 	if size >= -128 && size <= 127 {
 		return []byte{0x48, 0x83, 0xEC, byte(int8(size))}
 	}
+	// 128..255 do not fit SUB's unsigned imm8, but the Go assembler
+	// switches to ADDQ $-size, SP whose sign-extended imm8 does.
+	if size >= -255 && size <= 255 {
+		return []byte{0x48, 0x83, 0xC4, byte(int8(-size))}
+	}
 	return append([]byte{0x48, 0x81, 0xEC}, le32(int64(size))...)
 }