commit b76fcd465408d9daf23e15d9dcd1d17df1397e8f
author Bruce Lai <bruce.lai@sifive.com> Mon Jul 24 22:07:29 2023 -0700
committer libyuv LUCI CQ <libyuv-scoped@luci-project-accounts.iam.gserviceaccount.com> Tue Jul 25 09:21:59 2023 +0000
tree 4c345fa36e0b3db8bf0aed13263d17fea3acf0ff
parent 423e2b97eafc548f688d5cd79f1f3ef43785e0ba

[RISC-V] Support CMake build with custom compiler flags

This CL aims to support custom compiler flags.
Because upstream clang has supported to build for x280 with -mcpu=sifive-x280.

Change-Id: Ic8fbf026fe6805ac5c3422a9ccc3f53293c89570
Signed-off-by: Bruce Lai <bruce.lai@sifive.com>
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/4713191
Reviewed-by: Frank Barchard <fbarchard@chromium.org>
Commit-Queue: Frank Barchard <fbarchard@chromium.org>

docs/getting_started.md

diff --git a/docs/getting_started.md b/docs/getting_started.md
index d04e2d4..f2f71b8 100644
--- a/docs/getting_started.md
+++ b/docs/getting_started.md
@@ -238,6 +238,18 @@
           -DUSE_RVV=ON .
     cmake --build out/Release/
 
+#### Customized Compiler Flags
+
+Customized compiler flags are supported by `-DRISCV_COMPILER_FLAGS="xxx"`.
+If `-DRISCV_COMPILER_FLAGS="xxx"` is manually assigned, other compile flags(e.g disable -march=xxx) will not be appended.
+
+Example:
+
+    cmake -B out/Release/ -DUNIT_TEST=ON \
+          -DCMAKE_BUILD_TYPE=Release \
+          -DCMAKE_TOOLCHAIN_FILE="./riscv_script/riscv-clang.cmake" \
+          -DRISCV_COMPILER_FLAGS="-mcpu=sifive-x280" \
+          .
 
 ### Run on QEMU
 

riscv_script/riscv-clang.cmake

diff --git a/riscv_script/riscv-clang.cmake b/riscv_script/riscv-clang.cmake
index 47dd506..e287941 100644
--- a/riscv_script/riscv-clang.cmake
+++ b/riscv_script/riscv-clang.cmake
@@ -28,17 +28,20 @@
 set(CMAKE_OBJCOPY "${TOOLCHAIN_PATH}/bin/llvm-objcopy")
 
 # compile options
-message(STATUS "USE_RVV: ${USE_RVV}")
-message(STATUS "USE_AUTO_VECTORIZER: ${USE_AUTO_VECTORIZER}")
-set(RISCV_COMPILER_FLAGS)
-if(USE_RVV)
-  list(APPEND RISCV_COMPILER_FLAGS "-march=rv64gcv")
-  if(NOT USE_AUTO_VECTORIZER)
-    # Disable auto-vectorizer
-    add_compile_options(-fno-vectorize -fno-slp-vectorize)
+set(RISCV_COMPILER_FLAGS "" CACHE STRING "Compile flags")
+# if user provides RISCV_COMPILER_FLAGS, appeding compile flags is avoided.
+if(RISCV_COMPILER_FLAGS STREQUAL "")
+  message(STATUS "USE_RVV: ${USE_RVV}")
+  message(STATUS "USE_AUTO_VECTORIZER: ${USE_AUTO_VECTORIZER}")
+  if(USE_RVV)
+    list(APPEND RISCV_COMPILER_FLAGS "-march=rv64gcv")
+    if(NOT USE_AUTO_VECTORIZER)
+      # Disable auto-vectorizer
+      add_compile_options(-fno-vectorize -fno-slp-vectorize)
+    endif()
+  else()
+    list(APPEND RISCV_COMPILER_FLAGS "-march=rv64gc")
   endif()
-else()
-  list(APPEND RISCV_COMPILER_FLAGS "-march=rv64gc")
 endif()
 message(STATUS "RISCV_COMPILER_FLAGS: ${RISCV_COMPILER_FLAGS}")