[coreboot-gerrit] [XS] Change in coreboot[main]: soc/amd/psp_verstage: Add -Oz flag for clang

[Yu-Ping Wu (Code Review)]

Attention is currently required from: Arthur Heymans, Felix Held, Fred Reitberger, Jason Glenesk, Jérémy Compostella, Karthik Ramasubramanian, Martin L Roth, Matt DeVillier.

Yu-Ping Wu has posted comments on this change by Yu-Ping Wu. ( https://review.coreboot.org/c/coreboot/+/83594?usp=email )

Change subject: soc/amd/psp_verstage: Add -Oz flag for clang
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Patch Set 2:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/83594/comment/7b971ee2_99415d57?usp... :
PS1, Line 9: We have never intended to build ARM verstage with clang (see CB:69701).
> @[e-mail], Can you please try -Oz compiler optimization flag here - https://chromium. […]

The `-Oz` flag can solve the build issue. Guybrush has 148K `PSP_SRAM_SIZE` and 40K `PSP_VERSTAGE_STACK_SIZE`, leaving 108K for verstage plus the transfer buffer. The transfer buffer takes about 27K, so verstage must be less than 81K.

Some statistics of verstage size (from `_everstage - _verstage` in GOOGLE_GUYBRUSH/cbfs/fallback/verstage.map):

- gcc: 67K
- clang without `-Oz`: 81K
- clang with `-Oz`: 76K

Re-purposed this patch to add the `-Oz` flag as suggested.