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libgcc: Move cfa_how into potential padding in struct frame_state_reg_info

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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.
This commit is contained in:
Florian Weimer 2022-10-17 11:09:17 +02:00
parent 0f4815502d
commit acdb24166d
1 changed files with 6 additions and 5 deletions
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11
libgcc/unwind-dw2.h
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@ -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. */