[libunwind][ARM] Improve unwinder stack usage - Make WMMX support optional
These registers are only available on a limited set of ARM targets (those
based on XScale). Other targets should not have to pay the cost of these.
This patch shaves off about ~300 bytes of stack usage and ~1KB of code-size.
Differential revision: http://reviews.llvm.org/D21991
Reviewers: bcraig, compnerd
Change-Id: I2d7a1911a193bd70b123e78747e1a7d1482463c7
git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@274744 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 26c0228..3f0bfd6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -105,6 +105,7 @@
option(LIBUNWIND_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
option(LIBUNWIND_ENABLE_SHARED "Build libunwind as a shared library." ON)
option(LIBUNWIND_ENABLE_CROSS_UNWINDING "Enable cross-platform unwinding support." OFF)
+option(LIBUNWIND_ENABLE_ARM_WMMX "Enable unwinding support for ARM WMMX registers." OFF)
set(LIBUNWIND_TARGET_TRIPLE "" CACHE STRING "Target triple for cross compiling.")
set(LIBUNWIND_GCC_TOOLCHAIN "" CACHE PATH "GCC toolchain for cross compiling.")
@@ -237,6 +238,15 @@
list(APPEND LIBUNWIND_COMPILE_FLAGS -D_LIBUNWIND_IS_NATIVE_ONLY)
endif ()
+# ARM WMMX register support
+if (LIBUNWIND_ENABLE_ARM_WMMX)
+ # __ARM_WMMX is a compiler pre-define (as per the ACLE 2.0). Clang does not
+ # define this macro for any supported target at present. Therefore, here we
+ # provide the option to explicitly enable support for WMMX registers in the
+ # unwinder.
+ list(APPEND LIBUNWIND_COMPILE_FLAGS -D__ARM_WMMX)
+endif ()
+
# This is the _ONLY_ place where add_definitions is called.
if (MSVC)
add_definitions(-D_CRT_SECURE_NO_WARNINGS)