Bug 97208 - [gcc 10.2.0] Microblaze regression
Summary: [gcc 10.2.0] Microblaze regression
Status: RESOLVED WONTFIX
Alias: None
Product: gcc
Classification: Unclassified
Component: c (show other bugs)
Version: 10.2.0
: P3 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2020-09-25 13:21 UTC by Romain Naour
Modified: 2021-08-13 21:52 UTC (History)
1 user (show)

See Also:
Host:
Target: microblaze
Build:
Known to work:
Known to fail:
Last reconfirmed:

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Description Romain Naour 2020-09-25 13:21:58 UTC 
Hello,

Toolchains using gcc 10.2.0 targeting Microblaze architecture are not able to build a bootable Linux kernel 5.4.58 under Qemu (5.0.0).

https://gitlab.com/bootlin/toolchains-builder/-/jobs/729359542 (glibc)
https://gitlab.com/bootlin/toolchains-builder/-/jobs/729359544 (musl)
https://gitlab.com/bootlin/toolchains-builder/-/jobs/729359546 (uclibc-ng)

Toolchain components versions:
GCC 10.2
binutils 2.34
kernel headers 5.4.58

The same system boot as soon as gcc 9.3 is used.

Best regards,
Romain
Comment 1 Romain Naour 2020-09-26 21:16:01 UTC 
Hello, 

I had to disable -ftree-loop-distribute-patterns while building the kernel on microblaze (using -Os).

The regression appear since the commit [1] that moved -ftree-loop-distribute-patterns from -O3 to -O2 (-Os) optimization level.

I guess this behavior change should be documented in the gcc 10 changes page [2]?

[1] https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=5879ab5fafedc8f6f9bfe95a4cf8501b0df90edd

[2] https://gcc.gnu.org/gcc-10/changes.html

Best regards,
Romain
Comment 2 Richard Biener 2021-01-14 08:13:11 UTC 
It's a regular change of optimizations which are not fully documented.  Not a bug.
Comment 3 Giulio Benetti 2021-08-13 21:52:02 UTC 
This bug is still present on gcc version 11.1.0.