Code: Select all
'conditions': [
[ 'OS=="linux"', {
'target_defaults': {
'asflags': [
# Needed so that libs with .s files (e.g. libicudata.a)
# are compatible with the general 32-bit-ness.
'-32',
],
# All floating-point computations on x87 happens in 80-bit
# precision. Because the C and C++ language standards allow
# the compiler to keep the floating-point values in higher
# precision than what's specified in the source and doing so
# is more efficient than constantly rounding up to 64-bit or
# 32-bit precision as specified in the source, the compiler,
# especially in the optimized mode, tries very hard to keep
# values in x87 floating-point stack (in 80-bit precision)
# as long as possible. This has important side effects, that
# the real value used in computation may change depending on
# how the compiler did the optimization - that is, the value
# kept in 80-bit is different than the value rounded down to
# 64-bit or 32-bit. There are possible compiler options to make
# this behavior consistent (e.g. -ffloat-store would keep all
# floating-values in the memory, thus force them to be rounded
# to its original precision) but they have significant runtime
# performance penalty.
#
# -mfpmath=sse -msse2 makes the compiler use SSE instructions
# which keep floating-point values in SSE registers in its
# native precision (32-bit for single precision, and 64-bit for
# double precision values). This means the floating-point value
# used during computation does not change depending on how the
# compiler optimized the code, since the value is always kept
# in its specified precision.
'cflags': [
'-m32',
'-pthread',
'-march=pentium4',
'-fno-exceptions',
'-msse2',
'-mfpmath=sse',
],