x86/boot/compressed/64: Use TEST %reg,%reg instead of CMP $0,%reg

Use TEST %reg,%reg which sets the zero flag in the same way as CMP
$0,%reg, but the encoding uses one byte less.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20201029160258.139216-1-ubizjak@gmail.com

arch/x86/boot/compressed/head_64.S

@@ -241,12 +241,12 @@ SYM_FUNC_START(startup_32)
 	leal	rva(startup_64)(%ebp), %eax
 #ifdef CONFIG_EFI_MIXED
 	movl	rva(efi32_boot_args)(%ebp), %edi
-	cmp	$0, %edi
+	testl	%edi, %edi
 	jz	1f
 	leal	rva(efi64_stub_entry)(%ebp), %eax
 	movl	rva(efi32_boot_args+4)(%ebp), %esi
 	movl	rva(efi32_boot_args+8)(%ebp), %edx	// saved bootparams pointer
-	cmpl	$0, %edx
+	testl	%edx, %edx
 	jnz	1f
 	/*
 	 * efi_pe_entry uses MS calling convention, which requires 32 bytes of
@@ -592,7 +592,7 @@ SYM_CODE_START(trampoline_32bit_src)
 	movl	%eax, %cr0
 
 	/* Check what paging mode we want to be in after the trampoline */
-	cmpl	$0, %edx
+	testl	%edx, %edx
 	jz	1f
 
 	/* We want 5-level paging: don't touch CR3 if it already points to 5-level page tables */
@@ -622,7 +622,7 @@ SYM_CODE_START(trampoline_32bit_src)
 
 	/* Enable PAE and LA57 (if required) paging modes */
 	movl	$X86_CR4_PAE, %eax
-	cmpl	$0, %edx
+	testl	%edx, %edx
 	jz	1f
 	orl	$X86_CR4_LA57, %eax
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