Messages in this thread Patch in this message | | | From | Kanna Scarlet <> | Subject | [PATCH 1/1] x86: Change mov $0, %reg with xor %reg, %reg | Date | Thu, 4 Aug 2022 15:26:55 +0000 |
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Change mov $0, %reg with xor %reg, %reg because xor %reg, %reg is smaller so it is good to save space
asm: ba 00 00 00 00 movl $0x0,%edx 31 d2 xorl %edx,%edx
Suggested-by: Ammar Faizi <ammarfaizi2@gnuweeb.org> Signed-off-by: Kanna Scarlet <knscarlet@gnuweeb.org> --- arch/x86/boot/compressed/head_64.S | 2 +- arch/x86/boot/compressed/mem_encrypt.S | 2 +- arch/x86/kernel/ftrace_32.S | 4 ++-- arch/x86/kernel/head_64.S | 2 +- arch/x86/math-emu/div_Xsig.S | 2 +- arch/x86/math-emu/reg_u_sub.S | 2 +- 6 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index d33f060900d2..39442e7f5993 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -666,7 +666,7 @@ SYM_CODE_START(trampoline_32bit_src) movl %cr4, %eax andl $X86_CR4_MCE, %eax #else - movl $0, %eax + xorl %eax, %eax #endif /* Enable PAE and LA57 (if required) paging modes */ diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S index a73e4d783cae..d1e4d3aa8395 100644 --- a/arch/x86/boot/compressed/mem_encrypt.S +++ b/arch/x86/boot/compressed/mem_encrypt.S @@ -111,7 +111,7 @@ SYM_CODE_START(startup32_vc_handler) cmpl $0x72, 16(%esp) jne .Lfail - movl $0, %eax # Request CPUID[fn].EAX + xorl %eax, %eax # Request CPUID[fn].EAX movl %ebx, %edx # CPUID fn call sev_es_req_cpuid # Call helper testl %eax, %eax # Check return code diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S index a0ed0e4a2c0c..cff7decb58be 100644 --- a/arch/x86/kernel/ftrace_32.S +++ b/arch/x86/kernel/ftrace_32.S @@ -171,7 +171,7 @@ SYM_CODE_START(ftrace_graph_caller) movl 3*4(%esp), %eax /* Even with frame pointers, fentry doesn't have one here */ lea 4*4(%esp), %edx - movl $0, %ecx + xorl %ecx, %ecx subl $MCOUNT_INSN_SIZE, %eax call prepare_ftrace_return popl %edx @@ -184,7 +184,7 @@ SYM_CODE_END(ftrace_graph_caller) return_to_handler: pushl %eax pushl %edx - movl $0, %eax + xorl %eax, %eax call ftrace_return_to_handler movl %eax, %ecx popl %edx diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index d860d437631b..eeb06047e30a 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -184,7 +184,7 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) movq %cr4, %rcx andl $X86_CR4_MCE, %ecx #else - movl $0, %ecx + xorl %ecx, %ecx #endif /* Enable PAE mode, PGE and LA57 */ diff --git a/arch/x86/math-emu/div_Xsig.S b/arch/x86/math-emu/div_Xsig.S index 8c270ab415be..5767b4d23954 100644 --- a/arch/x86/math-emu/div_Xsig.S +++ b/arch/x86/math-emu/div_Xsig.S @@ -122,7 +122,7 @@ SYM_FUNC_START(div_Xsig) movl XsigLL(%esi),%eax rcrl %eax movl %eax,FPU_accum_1 - movl $0,%eax + xorl %eax,%eax rcrl %eax movl %eax,FPU_accum_0 diff --git a/arch/x86/math-emu/reg_u_sub.S b/arch/x86/math-emu/reg_u_sub.S index 4c900c29e4ff..130b49fa1ca2 100644 --- a/arch/x86/math-emu/reg_u_sub.S +++ b/arch/x86/math-emu/reg_u_sub.S @@ -212,7 +212,7 @@ L_must_be_zero: L_shift_32: movl %ebx,%eax movl %edx,%ebx - movl $0,%edx + xorl %edx,%edx subw $32,EXP(%edi) /* Can get underflow here */ /* We need to shift left by 1 - 31 bits */ -- Kanna Scarlet
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