PR for llvm/llvm-project#81084

[llvmbot]

resolves #81084

[llvmbot]

@MaskRay What do you think about merging this PR to the release branch?

[llvmbot]

@llvm/pr-subscribers-libunwind

Author: None (llvmbot)

Changes

resolves llvm/llvm-project#81084

---

Full diff: https://github.com/llvm/llvm-project/pull/81085.diff

1 Files Affected:

• (modified) libunwind/CMakeLists.txt (+19)

diff --git a/libunwind/CMakeLists.txt b/libunwind/CMakeLists.txt
index bb1b052f61d875..806d5a783ec39c 100644
--- a/libunwind/CMakeLists.txt
+++ b/libunwind/CMakeLists.txt
@@ -21,6 +21,7 @@ set(LIBUNWIND_LIBCXX_PATH "${CMAKE_CURRENT_LIST_DIR}/../libcxx" CACHE PATH
         "Specify path to libc++ source.")
 
 include(GNUInstallDirs)
+include(CheckSymbolExists)
 
 #===============================================================================
 # Setup CMake Options
@@ -96,6 +97,20 @@ endif()
 option(LIBUNWIND_HIDE_SYMBOLS
   "Do not export any symbols from the static library." ${LIBUNWIND_DEFAULT_HIDE_SYMBOLS})
 
+# If toolchain is FPXX, we switch to FP64 to save the full FPRs. See:
+# https://web.archive.org/web/20180828210612/https://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking
+check_symbol_exists(__mips_hard_float "" __MIPSHF)
+check_symbol_exists(_ABIO32 "" __MIPS_O32)
+if (__MIPSHF AND __MIPS_O32)
+  file(WRITE ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/mips_is_fpxx.c
+    "#if __mips_fpr != 0\n"
+    "# error\n"
+    "#endif\n")
+  try_compile(MIPS_FPABI_FPXX ${CMAKE_BINARY_DIR}
+    ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/mips_is_fpxx.c
+    CMAKE_FLAGS -DCMAKE_C_LINK_EXECUTABLE='echo')
+endif()
+
 #===============================================================================
 # Configure System
 #===============================================================================
@@ -179,6 +194,10 @@ if (WIN32)
   add_compile_flags_if_supported(-Wno-dll-attribute-on-redeclaration)
 endif()
 
+if (MIPS_FPABI_FPXX)
+  add_compile_flags(-mfp64)
+endif()
+
 # Get feature flags.
 # Exceptions
 # Catches C++ exceptions only and tells the compiler to assume that extern C