https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115912
Bug ID: 115912
Summary: [15 regression] Harfbuzz testsuite fails
(mvar_partial_instance test) since
r15-1901-g98914f9eba5f19
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: sjames at gcc dot gnu.org
CC: law at gcc dot gnu.org
Target Milestone: ---
Reproduction steps:
```
git clone https://github.com/harfbuzz/harfbuzz && cd harfbuzz
CFLAGS="-O2 -march=znver2 -fno-vect-cost-model" CXXFLAGS="-O2 -march=znver2
-fno-vect-cost-model" meson setup build --wipe
meson test -C build
```
Then can re-run just the bad test with adjusted paths as appropriate:
```
cd build
LD_LIBRARY_PATH=/home/sam/git/harfbuzz/build/src
/home/sam/git/harfbuzz/test/subset/run-tests.py util/hb-subset
/home/sam/git/harfbuzz/test/subset/data/tests/mvar_partial_instance.tests
```
The difference is:
```
<!-- Most of this table will be recalculated by the compiler -->
- <checkSumAdjustment value="0x5fad2240"/>
+ <checkSumAdjustment value="0xf5effee"/>
- <mapping from="-0.49994" to="-0.62744"/>
+ <mapping from="-0.49994" to="-0.00006"/>
- <mapping from="-0.24994" to="-0.2682"/>
+ <mapping from="-0.24994" to="-0.00006"/>
```
It looks suspicious that both values go to -0.00006. I'll narrow it down more
now.
