Enable static mimalloc in Spriv-Tools (#8419)

* Added optional mimalloc integration for SPIRV-Tools to improve
compilation performance
* Cloning `mimalloc` repo to external/ on demand during cmake config
* Enabled by default on Windows, configurable via
`SLANG_ENABLE_SPIRV_TOOLS_MIMALLOC` CMake option, to enable static
mimalloc build in spirv-tools.
* There are some crashes in Linux and Mac with static mimalloc enabled,
likely due to the system malloc and mimalloc mixed usage. This might be
expected as mimalloc in spirv-tools is not extensively tested according
to
https://github.com/KhronosGroup/SPIRV-Tools?tab=readme-ov-file#dependency-on-mimalloc.
So by default only Windows has this enabled.


Close: https://github.com/shader-slang/slang/issues/8158

---------

Co-authored-by: slangbot <ellieh+slangbot@nvidia.com>
Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

2 files changed, 70 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1ab208c2b..ab4556550 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -185,6 +185,11 @@ advanced_option(
     "Build using system glslang library"
     OFF
 )
+advanced_option(
+    SLANG_ENABLE_SPIRV_TOOLS_MIMALLOC
+    "Enable mimalloc for SPIRV-Tools to improve compilation performance"
+    OFF
+)
 
 option(
     SLANG_SPIRV_HEADERS_INCLUDE_DIR
diff --git a/external/CMakeLists.txt b/external/CMakeLists.txt
index faa8a5730..fed9e5e4e 100644
--- a/external/CMakeLists.txt
+++ b/external/CMakeLists.txt
@@ -25,6 +25,15 @@ if(NOT SLANG_ENABLE_EXTERNAL_COMPILER_WARNINGS)
     endif()
 endif()
 
+# Option to enable mimalloc for SPIRV-Tools to improve compilation performance
+if(WIN32)
+    option(
+        SLANG_ENABLE_SPIRV_TOOLS_MIMALLOC
+        "Enable mimalloc for SPIRV-Tools to improve compilation performance"
+        ON
+    )
+endif()
+
 # Unordered dense
 if(NOT ${SLANG_USE_SYSTEM_UNORDERED_DENSE})
     if(NOT SLANG_OVERRIDE_UNORDERED_DENSE_PATH)
@@ -147,6 +156,62 @@ if(SLANG_ENABLE_SLANG_GLSLANG)
         set(SPIRV_TOOLS_BUILD_STATIC ON)
         set(SPIRV_WERROR OFF)
         set(SPIRV_SKIP_TESTS ON)
+
+        # Enable mimalloc for SPIRV-Tools to improve compilation performance
+        # Based on SPIRV-Tools PR #6267: https://github.com/KhronosGroup/SPIRV-Tools/pull/6267
+        if(SLANG_ENABLE_SPIRV_TOOLS_MIMALLOC)
+            # Place mimalloc in slang/external instead of spirv-tools/external for better organization
+            set(MIMALLOC_PATH "${CMAKE_CURRENT_SOURCE_DIR}/mimalloc")
+
+            # Download mimalloc if it's not available
+            if(NOT EXISTS "${MIMALLOC_PATH}/CMakeLists.txt")
+                message(
+                    STATUS
+                    "mimalloc not found at ${MIMALLOC_PATH} - downloading..."
+                )
+                execute_process(
+                    COMMAND
+                        ${GIT_EXECUTABLE} clone --depth 1 --branch v2.1.7
+                        https://github.com/microsoft/mimalloc.git
+                        "${MIMALLOC_PATH}"
+                    RESULT_VARIABLE git_result
+                    OUTPUT_QUIET
+                    ERROR_QUIET
+                )
+                if(git_result EQUAL 0)
+                    # Point SPIRV-Tools to our mimalloc location
+                    set(mimalloc_SOURCE_DIR "${MIMALLOC_PATH}")
+                    set(SPIRV_TOOLS_USE_MIMALLOC ON)
+                    set(SPIRV_TOOLS_USE_MIMALLOC_IN_STATIC_BUILD ON)
+                    # set(MI_INSTALL_TOPLEVEL OFF)
+                    message(
+                        STATUS
+                        "Successfully downloaded and enabled mimalloc for SPIRV-Tools at ${MIMALLOC_PATH}"
+                    )
+                else()
+                    message(
+                        WARNING
+                        "Failed to download mimalloc. Building SPIRV-Tools without mimalloc support."
+                    )
+                endif()
+            endif()
+
+            # Check if mimalloc is available now
+            if(EXISTS "${MIMALLOC_PATH}/CMakeLists.txt")
+                # Point SPIRV-Tools to our mimalloc location
+                set(mimalloc_SOURCE_DIR "${MIMALLOC_PATH}")
+                set(SPIRV_TOOLS_USE_MIMALLOC ON)
+                # Also enable mimalloc in static builds for better performance
+                set(SPIRV_TOOLS_USE_MIMALLOC_IN_STATIC_BUILD ON)
+                # Disable mimalloc installation to avoid install target conflicts
+                # set(MI_INSTALL_TOPLEVEL OFF)
+                message(
+                    STATUS
+                    "Enabling mimalloc for SPIRV-Tools (including static builds) from ${MIMALLOC_PATH}"
+                )
+            endif()
+        endif()
+
         # Tools
         if(NOT SLANG_OVERRIDE_SPIRV_TOOLS_PATH)
             add_subdirectory(spirv-tools EXCLUDE_FROM_ALL ${system})