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Automatically use SSE registers for FP operations on i386 (#11853)

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use SSE for floating-point operations to avoid issues with improper fp-rounding and
loss of precision when moving fp-data to incompatible or less-precise
registers/storage locations

https://gcc.gnu.org/wiki/FloatingPointMath
https://gcc.gnu.org/wiki/x87note
This commit is contained in:
William L. DeRieux IV 2021-12-28 08:06:24 -05:00 committed by GitHub
parent 7f6306ca96
commit cc64a0405a
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 10 additions and 1 deletions
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1
CMakeLists.txt
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@ -286,7 +286,6 @@ endif()
# Subdirectories
# Be sure to add all relevant definitions above this
add_subdirectory(src)

10
src/CMakeLists.txt
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@ -769,6 +769,16 @@ else()
# - we don't deal with Inf/NaN or signed zero
set(MATH_FLAGS "-fno-math-errno -fno-trapping-math -ffinite-math-only -fno-signed-zeros")
# Enable SSE for floating point math on 32-bit x86 by default
# reasoning see minetest issue #11810 and https://gcc.gnu.org/wiki/FloatingPointMath
if(CMAKE_SIZEOF_VOID_P EQUAL 4)
check_c_source_compiles("#ifndef __i686__\n#error\n#endif\nint main(){}" IS_I686)
if(IS_I686)
message(STATUS "Detected Intel x86: using SSE instead of x87 FPU")
set(OTHER_FLAGS "${OTHER_FLAGS} -mfpmath=sse -msse")
endif()
endif()
set(CMAKE_CXX_FLAGS_RELEASE "-DNDEBUG ${RELEASE_WARNING_FLAGS} ${WARNING_FLAGS} ${OTHER_FLAGS} -Wall -pipe -funroll-loops")
if(CMAKE_SYSTEM_NAME MATCHES "(Darwin|BSD|DragonFly)")
set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -Os")