Detect metal version and propagate correctly for JIT (#1109)

* detect metal version and propagate correctly for JIT

* remove softmax

* fix versions

CMakeLists.txt

@@ -87,9 +87,11 @@ elseif (MLX_BUILD_METAL)
   if (${MACOS_VERSION} GREATER_EQUAL 14.2)
     set(METAL_CPP_PATCH ${CMAKE_CURRENT_SOURCE_DIR}/cmake/metal.14.2.diff)
     set(METAL_CPP_URL https://developer.apple.com/metal/cpp/files/metal-cpp_macOS14.2_iOS17.2.zip)
+    set(MLX_METAL_VERSION METAL_3_1)
   elseif (${MACOS_VERSION} GREATER_EQUAL 14.0)
     set(METAL_CPP_PATCH ${CMAKE_CURRENT_SOURCE_DIR}/cmake/metal.14.0.diff)
     set(METAL_CPP_URL https://developer.apple.com/metal/cpp/files/metal-cpp_macOS14_iOS17-beta.zip)
+    set(MLX_METAL_VERSION METAL_3_0)
   else()
     message(FATAL_ERROR "MLX requires macOS SDK >= 14.0 to be built with MLX_BUILD_METAL=ON" )
   endif()
@@ -111,6 +113,8 @@ elseif (MLX_BUILD_METAL)
     ${METAL_LIB}
     ${FOUNDATION_LIB}
     ${QUARTZ_LIB})
+
+  add_compile_definitions(${MLX_METAL_VERSION})
 endif()
 
 if (MLX_BUILD_CPU)

mlx/backend/metal/CMakeLists.txt

@@ -5,10 +5,16 @@ add_custom_command(
               ${CMAKE_CURRENT_BINARY_DIR}/compiled_preamble.cpp
               ${CMAKE_C_COMPILER}
               ${PROJECT_SOURCE_DIR}
+              "-D${MLX_METAL_VERSION}"
     DEPENDS make_compiled_preamble.sh
             kernels/compiled_preamble.h
             kernels/unary.h
             kernels/binary.h
+            kernels/bf16.h
+            kernels/erf.h
+            kernels/expm1f.h
+            kernels/utils.h
+            kernels/bf16_math.h
 )
 
 add_custom_target(

mlx/backend/metal/device.cpp

@@ -29,6 +29,14 @@ constexpr int MAX_DISPATCHES_PER_ENCODER = 2;
 
 constexpr const char* default_mtllib_path = METAL_PATH;
 
+constexpr auto get_metal_version() {
+#if defined METAL_3_1
+  return MTL::LanguageVersion3_1;
+#else
+  return MTL::LanguageVersion3_0;
+#endif
+}
+
 auto load_device() {
   auto devices = MTL::CopyAllDevices();
   auto device = static_cast<MTL::Device*>(devices->object(0))
@@ -275,7 +283,12 @@ MTL::Library* Device::get_library_(const std::string& source_string) {
       NS::String::string(source_string.c_str(), NS::ASCIIStringEncoding);
 
   NS::Error* error = nullptr;
-  auto mtl_lib = device_->newLibrary(ns_code, nullptr, &error);
+  auto options = MTL::CompileOptions::alloc()->init();
+  options->setFastMathEnabled(false);
+
+  options->setLanguageVersion(get_metal_version());
+  auto mtl_lib = device_->newLibrary(ns_code, options, &error);
+  options->release();
 
   // Throw error if unable to compile library
   if (!mtl_lib) {

mlx/backend/metal/kernels/CMakeLists.txt

@@ -39,7 +39,7 @@ set(
 )
 
 function(build_kernel_base TARGET SRCFILE DEPS)
-  set(METAL_FLAGS -Wall -Wextra -fno-fast-math)
+  set(METAL_FLAGS -Wall -Wextra -fno-fast-math -D${MLX_METAL_VERSION})
   if(MLX_METAL_DEBUG)
     set(METAL_FLAGS ${METAL_FLAGS}
         -gline-tables-only

mlx/backend/metal/kernels/bf16.h

@@ -6,7 +6,9 @@
 
 using namespace metal;
 
-#if defined(__HAVE_BFLOAT__)
+// No support for less than metal 3.0
+// anything greater has native bfloat
+#ifndef METAL_3_0
 
 typedef bfloat bfloat16_t;
 
@@ -312,6 +314,6 @@ METAL_FUNC bool isnan(_MLX_BFloat16 x) {
 
 #pragma METAL internals : disable
 
-#endif // defined(__HAVE_BFLOAT__)
+#endif
 
 #include "mlx/backend/metal/kernels/bf16_math.h"

mlx/backend/metal/kernels/bf16_math.h

@@ -369,7 +369,7 @@ instantiate_metal_math_funcs(
     return static_cast<otype>(__metal_simd_xor(static_cast<ctype>(data)));     \
   }
 
-#if defined(__HAVE_BFLOAT__)
+#ifndef METAL_3_0
 
 #define bfloat16_to_uint16(x) as_type<uint16_t>(x)
 #define uint16_to_bfloat16(x) as_type<bfloat16_t>(x)

mlx/backend/metal/make_compiled_preamble.sh

@@ -9,8 +9,9 @@
 OUTPUT_FILE=$1
 CC=$2
 SRCDIR=$3
+CFLAGS=$4
 
-CONTENT=$($CC -I $SRCDIR -E $SRCDIR/mlx/backend/metal/kernels/compiled_preamble.h 2>/dev/null)
+CONTENT=$($CC -I $SRCDIR -E $SRCDIR/mlx/backend/metal/kernels/compiled_preamble.h $CFLAGS 2>/dev/null)
 
 cat << EOF > "$OUTPUT_FILE"
 // Copyright © 2023-24 Apple Inc.