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From: George Hu <integral@archlinux.org>
To: grub-devel@gnu.org
Cc: Daniel Kiper <daniel.kiper@oracle.com>,
	Alex Burmashev <alexander.burmashev@oracle.com>,
	Vladimir 'phcoder' Serbinenko <phcoder@gmail.com>,
	George Hu <integral@archlinux.org>
Subject: [PATCH RESEND] lib/x86_64/setjmp: Use 32-bit zero idiom for shorter encoding
Date: Wed, 26 Nov 2025 16:45:46 +0800	[thread overview]
Message-ID: <20251126084545.163625-2-integral@archlinux.org> (raw)

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

Signed-off-by: George Hu <integral@archlinux.org>
---
 grub-core/lib/x86_64/setjmp.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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
-- 
2.52.0


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             reply	other threads:[~2025-11-26 14:15 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-26  8:45 George Hu [this message]
2025-12-18 17:28 ` [PATCH RESEND] lib/x86_64/setjmp: Use 32-bit zero idiom for shorter encoding Daniel Kiper

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