math: use fpclassify for isinf on PowerPC to avoid QEMU xststdcsp bug - #1421
Merged
Conversation
On PowerPC, avoid __builtin_isinf/__builtin_isinff — QEMU incorrectly emulates the xststdcsp instruction used by GCC 15+ for these builtins, causing subnormal floats to be misclassified as infinity. fpclassify() is immune to this bug on all GCC/QEMU versions.
fo40225
marked this pull request as ready for review
August 1, 2026 13:41
mr-c
approved these changes
Aug 3, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
On PowerPC, avoid __builtin_isinf/__builtin_isinff — QEMU incorrectly emulates the xststdcsp instruction used by GCC 15+ for these builtins, causing subnormal floats to be misclassified as infinity. fpclassify() is immune to this bug on all GCC/QEMU versions.