From: George Hu <integral@archlinux.org>
Date: Wed, 26 Nov 2025 08:45:46 +0000 (+0800)
Subject: lib/x86_64/setjmp: Use 32-bit zero idiom for shorter encoding
X-Git-Tag: grub-2.14~23
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=641646376b81593be9490864d56b25cd9922f630;p=thirdparty%2Fgrub.git

lib/x86_64/setjmp: Use 32-bit zero idiom for shorter encoding

Switch from "xorq %rax, %rax" to "xorl %eax, %eax". In 64-bit mode
zeroing EAX implicitly clears RAX and the 32-bit form encodes are one
byte smaller while keeping identical semantics.

Signed-off-by: George Hu <integral@archlinux.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---

diff --git a/grub-core/lib/x86_64/setjmp.S b/grub-core/lib/x86_64/setjmp.S
index 6b151bc4d..4c6c81249 100644
--- a/grub-core/lib/x86_64/setjmp.S
+++ b/grub-core/lib/x86_64/setjmp.S
@@ -36,7 +36,7 @@ GRUB_MOD_LICENSE "GPLv3+"
  */
 FUNCTION(grub_setjmp)
 	pop	%rsi		/* Return address, and adjust the stack */
-	xorq	%rax, %rax
+	xorl	%eax, %eax
 	movq	%rbx, 0(%rdi)	/* RBX */
 	movq	%rsp, 8(%rdi)   /* RSP */
 	push	%rsi