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authorRalf Baechle <ralf@linux-mips.org>2010-10-29 14:08:24 -0400
committerRalf Baechle <ralf@linux-mips.org>2010-10-29 14:08:24 -0400
commit7837314d141c661c70bc13c5050694413ecfe14a (patch)
treede137b1d2945d2490bc1dcdf6d76eac6006f7ab0 /arch/mips/include/asm/cmpxchg.h
parent18cb657ca1bafe635f368346a1676fb04c512edf (diff)
MIPS: Get rid of branches to .subsections.
It was a nice optimization - on paper at least. In practice it results in branches that may exceed the maximum legal range for a branch. We can fight that problem with -ffunction-sections but -ffunction-sections again is incompatible with -pg used by the function tracer. By rewriting the loop around all simple LL/SC blocks to C we reduce the amount of inline assembler and at the same time allow GCC to often fill the branch delay slots with something sensible or whatever else clever optimization it may have up in its sleeve. With this optimization gone we also no longer need -ffunction-sections, so drop it. This optimization was originally introduced in 2.6.21, commit 5999eca25c1fd4b9b9aca7833b04d10fe4bc877d (linux-mips.org) rsp. f65e4fa8e0c6022ad58dc88d1b11b12589ed7f9f (kernel.org). Original fix for the issues which caused me to pull this optimization by Paul Gortmaker <paul.gortmaker@windriver.com>. Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/include/asm/cmpxchg.h')
-rw-r--r--arch/mips/include/asm/cmpxchg.h7
1 files changed, 2 insertions, 5 deletions
diff --git a/arch/mips/include/asm/cmpxchg.h b/arch/mips/include/asm/cmpxchg.h
index 2d28017e95d0..d8d1c2805ac7 100644
--- a/arch/mips/include/asm/cmpxchg.h
+++ b/arch/mips/include/asm/cmpxchg.h
@@ -44,12 +44,9 @@
44 " move $1, %z4 \n" \ 44 " move $1, %z4 \n" \
45 " .set mips3 \n" \ 45 " .set mips3 \n" \
46 " " st " $1, %1 \n" \ 46 " " st " $1, %1 \n" \
47 " beqz $1, 3f \n" \ 47 " beqz $1, 1b \n" \
48 "2: \n" \
49 " .subsection 2 \n" \
50 "3: b 1b \n" \
51 " .previous \n" \
52 " .set pop \n" \ 48 " .set pop \n" \
49 "2: \n" \
53 : "=&r" (__ret), "=R" (*m) \ 50 : "=&r" (__ret), "=R" (*m) \
54 : "R" (*m), "Jr" (old), "Jr" (new) \ 51 : "R" (*m), "Jr" (old), "Jr" (new) \
55 : "memory"); \ 52 : "memory"); \