Fix kernel deps to reduce build times (#1205)

mlx/backend/metal/kernels/CMakeLists.txt

@@ -1,68 +1,12 @@
 set(
-  HEADERS
+  BASE_HEADERS
   bf16.h
   bf16_math.h
   complex.h
   defines.h
   utils.h
-  steel/conv/params.h
 )
 
-set(
-  KERNELS
-  "arg_reduce"
-  "conv"
-  "gemv"
-  "random"
-  "rms_norm"
-  "layer_norm"
-  "rope"
-  "scaled_dot_product_attention"
-)
-
-if (NOT MLX_METAL_JIT)
-set(
-  KERNELS
-  ${KERNELS}
-  "arange"
-  "binary"
-  "binary_two"
-  "unary"
-  "ternary"
-  "copy"
-  "fft"
-  "quantized"
-  "softmax"
-  "sort"
-  "scan"
-  "reduce"
-)
-set(
-  HEADERS 
-  ${HEADERS}
-  atomic.h
-  arange.h
-  unary_ops.h
-  unary.h
-  binary_ops.h
-  binary.h
-  ternary.h
-  copy.h
-  fft.h
-  fft/radix.h
-  fft/readwrite.h
-  quantized.h
-  softmax.h
-  sort.h
-  scan.h
-  reduction/ops.h
-  reduction/reduce_init.h
-  reduction/reduce_all.h
-  reduction/reduce_col.h
-  reduction/reduce_row.h
-)
-endif()
-
 function(build_kernel_base TARGET SRCFILE DEPS)
   set(METAL_FLAGS -Wall -Wextra -fno-fast-math -D${MLX_METAL_VERSION})
   if(MLX_METAL_DEBUG)
@@ -76,7 +20,7 @@ function(build_kernel_base TARGET SRCFILE DEPS)
                   -c ${SRCFILE}
                   -I${PROJECT_SOURCE_DIR}
                   -o ${TARGET}.air
-    DEPENDS ${SRCFILE} ${DEPS}
+    DEPENDS ${SRCFILE} ${DEPS} ${BASE_HEADERS}
     OUTPUT ${TARGET}.air
     COMMENT "Building ${TARGET}.air"
     VERBATIM
@@ -85,24 +29,27 @@ endfunction(build_kernel_base)
 
 function(build_kernel KERNEL)
   set(SRCFILE ${CMAKE_CURRENT_SOURCE_DIR}/${KERNEL}.metal)
-  build_kernel_base(${KERNEL} ${SRCFILE} "${HEADERS}")
+  cmake_path(GET KERNEL STEM TARGET)
+  build_kernel_base(${TARGET} ${SRCFILE} "${ARGN}")
+  set(KERNEL_AIR ${TARGET}.air ${KERNEL_AIR} PARENT_SCOPE)
 endfunction(build_kernel)
 
-foreach(KERNEL ${KERNELS})
-  build_kernel(${KERNEL})
-  set(KERNEL_AIR ${KERNEL}.air ${KERNEL_AIR})
-endforeach()
+build_kernel(arg_reduce)
+build_kernel(conv steel/conv/params.h)
+build_kernel(gemv steel/utils.h)
+build_kernel(layer_norm)
+build_kernel(random)
+build_kernel(rms_norm)
+build_kernel(rope)
+build_kernel(
+  scaled_dot_product_attention
+  scaled_dot_product_attention_params.h
+  steel/defines.h
+  steel/gemm/transforms.h
+  steel/utils.h
+)
 
-if (NOT MLX_METAL_JIT)
-  set(
-    STEEL_KERNELS
-    ${CMAKE_CURRENT_SOURCE_DIR}/steel/conv/kernels/steel_conv.metal
-    ${CMAKE_CURRENT_SOURCE_DIR}/steel/conv/kernels/steel_conv_general.metal
-    ${CMAKE_CURRENT_SOURCE_DIR}/steel/gemm/kernels/steel_gemm_fused.metal
-    ${CMAKE_CURRENT_SOURCE_DIR}/steel/gemm/kernels/steel_gemm_masked.metal
-    ${CMAKE_CURRENT_SOURCE_DIR}/steel/gemm/kernels/steel_gemm_splitk.metal
-  )
-  set(
+set(
   STEEL_HEADERS 
   steel/defines.h
   steel/utils.h
@@ -120,14 +67,61 @@ if (NOT MLX_METAL_JIT)
   steel/gemm/kernels/steel_gemm_fused.h
   steel/gemm/kernels/steel_gemm_masked.h
   steel/gemm/kernels/steel_gemm_splitk.h
-  )
-  foreach(KERNEL ${STEEL_KERNELS})
-    cmake_path(GET KERNEL STEM TARGET)
-    build_kernel_base(${TARGET} ${KERNEL} "${STEEL_HEADERS}")
-    set(KERNEL_AIR ${TARGET}.air ${KERNEL_AIR})
-  endforeach()
+)
+
+if (NOT MLX_METAL_JIT)
+build_kernel(arange arange.h)
+build_kernel(binary binary.h binary_ops.h)
+build_kernel(binary_two binary_two.h)
+build_kernel(copy copy.h)
+build_kernel(
+  fft
+  fft.h
+  fft/radix.h
+  fft/readwrite.h
+)
+build_kernel(
+  reduce
+  atomic.h
+  reduction/ops.h
+  reduction/reduce_init.h
+  reduction/reduce_all.h
+  reduction/reduce_col.h
+  reduction/reduce_row.h
+)
+build_kernel(
+  quantized
+  quantized.h
+  ${STEEL_HEADERS}
+)
+build_kernel(scan scan.h)
+build_kernel(softmax softmax.h)
+build_kernel(sort sort.h)
+build_kernel(ternary ternary.h ternary_ops.h)
+build_kernel(unary unary.h unary_ops.h)
+build_kernel(
+  steel/conv/kernels/steel_conv
+  ${STEEL_HEADERS}
+)
+build_kernel(
+  steel/conv/kernels/steel_conv_general
+  ${STEEL_HEADERS}
+)
+build_kernel(
+  steel/gemm/kernels/steel_gemm_fused
+  ${STEEL_HEADERS}
+)
+build_kernel(
+  steel/gemm/kernels/steel_gemm_masked
+  ${STEEL_HEADERS}
+)
+build_kernel(
+  steel/gemm/kernels/steel_gemm_splitk
+  ${STEEL_HEADERS}
+)
 endif()
 
+
 add_custom_command(
   OUTPUT ${MLX_METAL_PATH}/mlx.metallib
   COMMAND xcrun -sdk macosx metallib ${KERNEL_AIR} -o ${MLX_METAL_PATH}/mlx.metallib