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Bug 1429961
| Summary: | vec_vmul{e,o}u{b,h} AltiVec built-in functions broken on ppc64 and ppc64le | ||
|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | Nikola Forró <nforro> |
| Component: | gcc | Assignee: | Jakub Jelinek <jakub> |
| Status: | CLOSED RAWHIDE | QA Contact: | Fedora Extras Quality Assurance <extras-qa> |
| Severity: | unspecified | Docs Contact: | |
| Priority: | unspecified | ||
| Version: | 26 | CC: | davejohansen, jakub, jwakely, law, mpolacek |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | ppc64 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2017-05-23 13:22:07 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
This is fixed since gcc-7.0.1-0.15.fc26, right? Already since gcc-7.0.1-0.13.fc26. |
Description of problem: vec_vmul{e,o}u{b,h} functions return incorrect results, because they compile down to instructions that differ in signedness, e.g. vec_vmuleub function compiles down to the vmulesb instruction. This also applies to generic vec_mule and vec_mulo functions when they are used with a pair of unsigned char or unsigned short arguments. Version-Release number of selected component (if applicable): gcc-7.0.1-0.10.fc26 How reproducible: always Steps to Reproduce: 1. $ cat reproducer.c #include <limits.h> #include <assert.h> #include <altivec.h> int main(void) { vector unsigned char v0 = {1, 0, 0, 0, 0, 0, 0, 0}; vector unsigned char v1 = {UCHAR_MAX, 0, 0, 0, 0, 0, 0, 0}; vector unsigned short res = vec_vmuleub(v0, v1); assert(res[0] == (unsigned short)v0[0] * (unsigned short)v1[0]); } 2. $ gcc -maltivec -mabi=altivec reproducer.c -o reproducer 3. $ ./reproducer reproducer: reproducer.c:12: main: Assertion `res[0] == (unsigned short)v0[0] * (unsigned short)v1[0]' failed. Aborted (core dumped) Actual results: assertion fails Expected results: assertion succeeds Additional info: This affects build of libjpeg-turbo, making it generate broken images.