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Swap out -ffast-math for a safe subset of optimization flags (#9682)

It caused more trouble than its worth.
fixes #3943, fixes #5330
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sfan5 committed Apr 16, 2020
1 parent e8ac5a3 commit 5cbe8437a8f7efc9c76baf23de700e96ad96b385
Showing with 9 additions and 1 deletion.
  1. +6 −1 src/CMakeLists.txt
  2. +3 −0 src/collision.cpp
@@ -713,6 +713,11 @@ else()
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DWIN32_LEAN_AND_MEAN")
endif()

# Use a safe subset of flags to speed up math calculations:
# - we don't need errno or math exceptions
# - 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")

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")
@@ -723,7 +728,7 @@ else()
AND CMAKE_CXX_COMPILER_VERSION MATCHES "^9\\.")
# Clang 9 has broken -ffast-math on glibc
else()
set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -ffast-math")
set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} ${MATH_FLAGS}")
endif()
endif(CMAKE_SYSTEM_NAME MATCHES "(Darwin|BSD|DragonFly)")
set(CMAKE_CXX_FLAGS_SEMIDEBUG "-g -O1 -Wall -Wabi ${WARNING_FLAGS} ${OTHER_FLAGS}")
@@ -32,6 +32,9 @@ with this program; if not, write to the Free Software Foundation, Inc.,
#include "util/timetaker.h"
#include "profiler.h"

#ifdef __FAST_MATH__
#warning "-ffast-math is known to cause bugs in collision code, do not use!"
#endif

struct NearbyCollisionInfo {
NearbyCollisionInfo(bool is_ul, bool is_obj, int bouncy,

1 comment on commit 5cbe843

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@oilboi oilboi commented on 5cbe843 Apr 17, 2020

Works great

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