Hi Jackson,
The issue is that some of our libraries which are linked into the secure image have LTO enabled.
Per https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html: The important thing to keep in mind is that to enable link-time optimizations you need to use the GCC driver to perform the link step. GCC automatically performs link-time optimization if any of the objects involved were compiled with the -flto command-line option. You can always override the automatic decision to do link-time optimization by passing -fno-lto to the link command.
So it seems that the -fno-lto flag must be used to explicitly opt out of LTO.
It might be wise to add that flag to toolchain_GNUARM.cmake to ensure no one is unknowingly having LTO enabled as you have not analyzed the impact.
Regards, Brian
From: Jackson Cooper-Driver Jackson.Cooper-Driver@arm.com Sent: Wednesday, April 2, 2025 1:46 AM To: tf-m@lists.trustedfirmware.org; Quach, Brian brian@ti.com; Antonio De Angelis Antonio.DeAngelis@arm.com Subject: [EXTERNAL] Re: Link Time Optimization
Hi Brian, Worth just saying that GCC does not enable any optimizations by default. LTO needs to be explicitly enabled on the command line using -flto - see the GCC docs here - https: //gcc. gnu. org/onlinedocs/gcc/Optimize-Options. html CMake also ZjQcmQRYFpfptBannerStart This message was sent from outside of Texas Instruments.
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ZjQcmQRYFpfptBannerEnd Hi Brian,
Worth just saying that GCC does not enable any optimizations by default. LTO needs to be explicitly enabled on the command line using -flto - see the GCC docs here - https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.htmlhttps://urldefense.com/v3/__https:/gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html__;!!G3vK!VU8ng_LK4ryG6ctsxN9oC0C_W4zybehjT8Hvkiv80VjMfcPsFIYjBLlgN3deEvFCTGiWzOk49XdJ2UjQOA$
CMake also has a way to enable LTO using a specific CMake flag which you can set - details here - https://stackoverflow.com/questions/31355692/how-do-i-enable-link-time-optim...https://urldefense.com/v3/__https:/stackoverflow.com/questions/31355692/how-do-i-enable-link-time-optimization-lto-with-cmake__;!!G3vK!VU8ng_LK4ryG6ctsxN9oC0C_W4zybehjT8Hvkiv80VjMfcPsFIYjBLlgN3deEvFCTGiWzOk49Xct_H-d_Q$ But we do not currently do that in TF-M
Thanks, Jackson ________________________________ From: Antonio De Angelis via TF-M <tf-m@lists.trustedfirmware.orgmailto:tf-m@lists.trustedfirmware.org> Sent: 01 April 2025 22:44 To: tf-m@lists.trustedfirmware.orgmailto:tf-m@lists.trustedfirmware.org <tf-m@lists.trustedfirmware.orgmailto:tf-m@lists.trustedfirmware.org>; Quach, Brian <brian@ti.commailto:brian@ti.com> Subject: [TF-M] Re: Link Time Optimization
Hi Brian,
no, TF-M does not use it (on purpose), i.e. if GCC enables it by default, the impact of LTO has not been assessed.
Thanks, Antonio ________________________________ From: Quach, Brian via TF-M <tf-m@lists.trustedfirmware.orgmailto:tf-m@lists.trustedfirmware.org> Sent: Tuesday, April 1, 2025 16:01 To: tf-m@lists.trustedfirmware.orgmailto:tf-m@lists.trustedfirmware.org <tf-m@lists.trustedfirmware.orgmailto:tf-m@lists.trustedfirmware.org> Subject: [TF-M] Link Time Optimization
Hi, does TF-M use LTO? I didn’t see any flags to disable it in toolchain_GNUARM.cmake. I think for GCC, it’s enabled by default if no flag is set.
Regards,
Brian Quach
SimpleLink MCU
Texas Instruments Inc.
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