| Issue |
137332
|
| Summary |
clang++-20 incorrect instruction encoding for VPDPBUSD on znver5 (only)
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
gcp
|
Steps to reproduce:
1. git clone https://github.com/official-stockfish/Stockfish.git
2. cd stockfish/src
3. Apply this patch to force `march=znver5`
```
diff --git a/src/Makefile b/src/Makefile
index 76b94785..f65f6f90 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -626,7 +626,7 @@ endif
### 3.3 Optimization
ifeq ($(optimize),yes)
- CXXFLAGS += -O3 -funroll-loops
+ CXXFLAGS += -O3 -funroll-loops -march=znver5 -mtune=znver5
ifeq ($(comp),gcc)
ifeq ($(OS), Android)
```
4. Compile with `make build ARCH=x86-64-vnni512 COMP=clang CXX=clang++-20 CC=clang-20 LD=ldd-20`
5. Run the binary on a Zen5 system, type `go infinite`
6. Program crashes in:
=> 0x00005555555b73ae <+5998>: {vex} vpdpbusd 0xc580(%rcx),%ymm0,%ymm1
If I have to guess, due to some issue with AVXVNNI vs VNNI512 encoding. This does not happen if you target znver4.
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