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arch/x86/bootblock_crt0.S: Leverage eax in protected mode entry 

Leverage already used eax register in bootblock_protected_mode_entry.
Avoid another register ebx just for preserving eax value as it is not
needed and is not used at all after moving the value into mm0.
Allow EBX to be preserved for other usage.

Change-Id: Ia668b78f2f97cf026692f1fe63ff8a382a162474
Signed-off-by: Himanshu Sahdev <himanshusah@hcl.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35292
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
This commit is contained in:
Himanshu Sahdev aka CunningLearner 2019-09-08 12:29:27 +05:30 committed by Patrick Georgi
parent 7f50afb0c7
commit 2b84008ed9
1 changed files with 1 additions and 2 deletions
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src/arch/x86/bootblock_crt0.S
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@ -47,11 +47,10 @@ bootblock_protected_mode_entry:
/* MMX registers required here */ /* MMX registers required here */
/* BIST result in eax */ /* BIST result in eax */
movl %eax, %ebx movd %eax, %mm0
/* Get an early timestamp */ /* Get an early timestamp */
rdtsc rdtsc
movd %ebx, %mm0
movd %eax, %mm1 movd %eax, %mm1
movd %edx, %mm2 movd %edx, %mm2
#endif #endif