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Make "-mpreferred-stack-boundary=2" the default on the i386.

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This reduces the size of the kernel and modules when compiled with GCC 2.95.
This commit is contained in:
David E. O'Brien 1999-11-17 07:30:35 +00:00
parent a8d46c3a99
commit 54d477a4f1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=53265
2 changed files with 26 additions and 0 deletions
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13
share/mk/bsd.kern.mk
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@ -18,6 +18,19 @@ CWARNFLAGS?= -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
# of material assistance.
#
#
# On the i386, do not align the stack to 16-byte boundaries. Otherwise GCC
# 2.95 adds code to the entry and exit point of every function to align the
# stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
# per function call. While the 16-byte alignment may benefit micro benchmarks,
# it is probably an overall loose as it makes the code bigger (less efficient
# use of code cache tag lines) and uses more stack (less efficient use of data
# cache tag lines)
#
.if ${MACHINE_ARCH} == "i386"
CFLAGS+= -mpreferred-stack-boundary=2
.endif
#
# On the alpha, make sure that we don't use floating-point registers and
# allow the use of EV56 instructions (only needed for low-level i/o).

13
sys/conf/kern.mk
View File

@ -18,6 +18,19 @@ CWARNFLAGS?= -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
# of material assistance.
#
#
# On the i386, do not align the stack to 16-byte boundaries. Otherwise GCC
# 2.95 adds code to the entry and exit point of every function to align the
# stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
# per function call. While the 16-byte alignment may benefit micro benchmarks,
# it is probably an overall loose as it makes the code bigger (less efficient
# use of code cache tag lines) and uses more stack (less efficient use of data
# cache tag lines)
#
.if ${MACHINE_ARCH} == "i386"
CFLAGS+= -mpreferred-stack-boundary=2
.endif
#
# On the alpha, make sure that we don't use floating-point registers and
# allow the use of EV56 instructions (only needed for low-level i/o).