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Remove -fno-guess-branch-probability and -fno-unit-at-a-time.

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bde enabled -fno-guess-branch-probability in 2003, well before our
current compiler was imported. At the time it produced weirdly orded
code. It no longer does that. It also saves 0-4 bytes depending on
other options.

kan disabled unit-at-a-time in 2004 because it badly mangled boot2 so
it wouldn't work. That too was before the 4.2.1 compiler, where it no
longer does that. This saves 44 bytes.

I had planned to document why they were needed, but when I discovered
their antiquity, I removed them and boot2 still works and is
smaller. In qemu, the old and new boot2's behaved identically.

These are gcc specific hacks, and won't affect clang-built boot2
at all.
This commit is contained in:
Warner Losh 2017-03-28 18:09:01 +00:00
parent 10f81a9b3b
commit df4fcca522
1 changed files with 0 additions and 2 deletions
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2
sys/boot/i386/boot2/Makefile
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@ -38,8 +38,6 @@ CFLAGS= -fomit-frame-pointer \
-Winline
CFLAGS.gcc+= -Os \
-fno-guess-branch-probability \
-fno-unit-at-a-time \
--param max-inline-insns-single=100
.if ${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} <= 40201
CFLAGS.gcc+= -mno-align-long-strings