metal : use constexpr in FA kernels

ggml-ci

Author: ggerganov

ggml/src/ggml-metal/ggml-metal.metal

@@ -3128,14 +3128,15 @@ kernel void kernel_flash_attn_ext(
     const int iq2 = tgpig[1];
     const int iq1 = tgpig[0]*Q;
 
-    const short DK4  = DK/4;
-    const short DK8  = DK/8;
-    const short DK16 = DK/16;
-    const short DV4  = DV/4;
-    const short DV8  = DV/8;
-    const short DV16 = DV/16;
-    const short NW  = N_SIMDWIDTH;
-    const short SH  = (2*C + Q); // shared memory per simdgroup (s_t == float)
+    constexpr short DK4  = DK/4;
+    constexpr short DK8  = DK/8;
+    constexpr short DK16 = DK/16;
+    constexpr short DV4  = DV/4;
+    constexpr short DV8  = DV/8;
+    constexpr short DV16 = DV/16;
+
+    constexpr short NW  = N_SIMDWIDTH;
+    constexpr short SH  = (2*C + Q); // shared memory per simdgroup (s_t == float)
 
     const short TS = nsg*SH;   // shared memory size per query in (s_t == float)
     const short T  = DK + 2*TS; // shared memory size per query in (half)
@@ -3641,11 +3642,11 @@ kernel void kernel_flash_attn_ext_vec(
     const int iq2 = tgpig[1];
     const int iq1 = tgpig[0];
 
-    const short DK4 = DK/4;
-    const short DV4 = DV/4;
-    const short NW  = N_SIMDWIDTH;
-    const short NL  = NW/NE; // note: this can be adjusted to support different head sizes and simdgroup work loads
-    const short SH  = 2*C;   // shared memory per simdgroup
+    constexpr short DK4 = DK/4;
+    constexpr short DV4 = DV/4;
+    constexpr short NW  = N_SIMDWIDTH;
+    constexpr short NL  = NW/NE; // note: this can be adjusted to support different head sizes and simdgroup work loads
+    constexpr short SH  = 2*C;   // shared memory per simdgroup
 
     const short T = DK + nsg*SH; // shared memory size per query in (half)