refactor: Work around gcc compiler bug 90348 #15959
Conversation
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Wouldn't it be better to just add |
The one doesn't rule out the other, though I would personally feel more comfortable with that solution. It's unclear to me what else this bug might potentially affect. |
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Concept ACK on working around the GCC issue but I agree with @luke-jr and @laanwj that introducing I think we should add |
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Ok, marking up for grabs for someone to change the build system. |
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I would expect -fno-inline-small-functions to be devastating for performance and I also believe would not completely work around the bug. I believe -fstack-reuse=none would be a more correct, and less impacting, workaround. |
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I wonder if there's a reliable compile test we could have configure run to detect the actual bug? |
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The test case from the gcc bug wouldn't work? And if disabling fstack-reuse isn't too expensive, we might just do it unconditionally? |
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I would also expect that -fstack-reuse=none has less impact than -fno-inline-small-functions, but benchmarks would be nice. I'll PR the reproduction bug as a unit test. |
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stack-reuse=none also has the advantage of turning some lifetime management bugs into less-bugs (which is AFAICT why the option exists). I would expect it to increase stack usage, which right now we're not currently particularly careful with. |
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@luke-jr on reliability, I think we'd be better off detecting versions than trying to use the test case. Unfortunately, it's unclear what versions this will be fixed in: (so far) it appears that this is actually hard for GCC to fix without severely gimping optimization. FWIW, the test case does not fail on PPC but I am moderately confident that bug exists there (it might be just that the larger redzone on PPC results in a different stack layout). |
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Yes, |
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Thanks everyone for the input, closing in favour of
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faf38bc build with -fstack-reuse=none (MarcoFalke) Pull request description: All versions of gcc that we commonly use for building are subject to bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90348. To work around that, set `-fstack-reuse=none` for all builds. See #15959 (comment) This option does not exist for clang https://clang.llvm.org/docs/ClangCommandLineReference.html#target-independent-compilation-options, but it does for gcc https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html ACKs for commit faf38b: Tree-SHA512: f5597583402d31ea7b89ac358a6f4a537bbb82a1dde2bd41bac65ee0fd88c7af75ee4c24c6b8eed6b139bf4dbf07ab2987f8fc30fb3eab179cd2d753a8a2a47d
faf38bc build with -fstack-reuse=none (MarcoFalke) Pull request description: All versions of gcc that we commonly use for building are subject to bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90348. To work around that, set `-fstack-reuse=none` for all builds. See bitcoin#15959 (comment) This option does not exist for clang https://clang.llvm.org/docs/ClangCommandLineReference.html#target-independent-compilation-options, but it does for gcc https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html ACKs for commit faf38b: Tree-SHA512: f5597583402d31ea7b89ac358a6f4a537bbb82a1dde2bd41bac65ee0fd88c7af75ee4c24c6b8eed6b139bf4dbf07ab2987f8fc30fb3eab179cd2d753a8a2a47d
faf38bc build with -fstack-reuse=none (MarcoFalke) Pull request description: All versions of gcc that we commonly use for building are subject to bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90348. To work around that, set `-fstack-reuse=none` for all builds. See bitcoin#15959 (comment) This option does not exist for clang https://clang.llvm.org/docs/ClangCommandLineReference.html#target-independent-compilation-options, but it does for gcc https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html ACKs for commit faf38b: Tree-SHA512: f5597583402d31ea7b89ac358a6f4a537bbb82a1dde2bd41bac65ee0fd88c7af75ee4c24c6b8eed6b139bf4dbf07ab2987f8fc30fb3eab179cd2d753a8a2a47d
6 participants
The gcc compiler creates "optimized" code (
-finline-small-functions) that modifiesina second time after it has been initialized with random bits.Working around the bug can be achieved in different ways: Moving
ininto a newconstarray, rearranging the loop to break the optimization, or moving the array into the outer scope, ...This fix is needed to release 0.18.1 on 32 bit platforms, thus needs backport.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90348
Fixes #14580