[MIPS] Improve branch prediction in ll/sc atomic operations.
Now that finally all supported versions of binutils have functioning
support for .subsection use .subsection to tweak the branch prediction
I did not modify the R10000 errata variants because it seems unclear if
this will invalidate the workaround which actually relies on the cheesy
prediction of branch likely to cause a misspredict if the sc was
successful.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/include/asm-mips/system.h b/include/asm-mips/system.h
index 5e1289c..597a374 100644
--- a/include/asm-mips/system.h
+++ b/include/asm-mips/system.h
@@ -110,7 +110,10 @@
" move %2, %z4 \n"
" .set mips3 \n"
" sc %2, %1 \n"
- " beqz %2, 1b \n"
+ " beqz %2, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (retval), "=m" (*m), "=&r" (dummy)
: "R" (*m), "Jr" (val)
@@ -155,7 +158,10 @@
"1: lld %0, %3 # xchg_u64 \n"
" move %2, %z4 \n"
" scd %2, %1 \n"
- " beqz %2, 1b \n"
+ " beqz %2, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (retval), "=m" (*m), "=&r" (dummy)
: "R" (*m), "Jr" (val)
@@ -232,8 +238,11 @@
" move $1, %z4 \n"
" .set mips3 \n"
" sc $1, %1 \n"
- " beqz $1, 1b \n"
+ " beqz $1, 3f \n"
"2: \n"
+ " .subsection 2 \n"
+ "3: b 1b \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (retval), "=R" (*m)
: "R" (*m), "Jr" (old), "Jr" (new)
@@ -283,8 +292,11 @@
" bne %0, %z3, 2f \n"
" move $1, %z4 \n"
" scd $1, %1 \n"
- " beqz $1, 1b \n"
+ " beqz $1, 3f \n"
"2: \n"
+ " .subsection 2 \n"
+ "3: b 1b \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (retval), "=R" (*m)
: "R" (*m), "Jr" (old), "Jr" (new)
