Fix BNB_WARP_SIZE detection for HIP host compilation pass

__GFX9__ is only defined during the device compilation pass, not
during host compilation. This caused BNB_WARP_SIZE to be 32 on
the host pass even for gfx942 (CDNA, warp=64), making the
conditional WARP_TRANSPOSE vs DIRECT selection wrong.

Use __AMDGCN_WAVEFRONT_SIZE instead, which the HIP compiler
defines correctly in both host and device passes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: TimDettmers

csrc/common.cuh

@@ -12,11 +12,12 @@
 // ============================================================================
 
 #if BNB_HIP
-// AMD GFX9 (CDNA) uses 64-wide warps; RDNA uses 32-wide
-#ifdef __GFX9__
-#define BNB_WARP_SIZE 64
+// Use the compiler-provided wavefront size, which is correctly defined in
+// both host and device compilation passes. CDNA (gfx9xx) = 64, RDNA = 32.
+#ifdef __AMDGCN_WAVEFRONT_SIZE
+#define BNB_WARP_SIZE __AMDGCN_WAVEFRONT_SIZE
 #else
-#define BNB_WARP_SIZE 32
+#define BNB_WARP_SIZE 64 // Safe default for HIP (matches CDNA)
 #endif
 #else
 #define BNB_WARP_SIZE 32