From acdb24166d13d87c374e578d2ad5d58249171930 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Mon, 17 Oct 2022 11:09:17 +0200
Subject: [PATCH] libgcc: Move cfa_how into potential padding in struct
frame_state_reg_info
On many architectures, there is a padding gap after the how array
member, and cfa_how can be moved there. This reduces the size of the
struct and the amount of memory that uw_frame_state_for has to clear.
There is no measurable performance benefit from this on x86-64 (even
though the memset goes from 120 to 112 bytes), but it seems to be a
good idea to do anyway.
libgcc/
* unwind-dw2.h (struct frame_state_reg_info): Move cfa_how member
and reduce its size.
---
libgcc/unwind-dw2.h | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/libgcc/unwind-dw2.h b/libgcc/unwind-dw2.h
index af34e000f07e..a0834b18277e 100644
--- a/libgcc/unwind-dw2.h
+++ b/libgcc/unwind-dw2.h
@@ -50,6 +50,12 @@ typedef struct
} reg[__LIBGCC_DWARF_FRAME_REGISTERS__+1];
unsigned char how[__LIBGCC_DWARF_FRAME_REGISTERS__+1];
+ enum {
+ CFA_UNSET,
+ CFA_REG_OFFSET,
+ CFA_EXP
+ } cfa_how : 8;
+
/* Used to implement DW_CFA_remember_state. */
struct frame_state_reg_info *prev;
@@ -58,11 +64,6 @@ typedef struct
_Unwind_Sword cfa_offset;
_Unwind_Word cfa_reg;
const unsigned char *cfa_exp;
- enum {
- CFA_UNSET,
- CFA_REG_OFFSET,
- CFA_EXP
- } cfa_how;
} regs;
/* The PC described by the current frame state. */
--
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