MIPS: bitops.h: Avoid inline asm for constant FLS
GCC is smart enough to substitute the final result for FLS calculations
as implemented in the fallback C code we have in `__fls' and `fls'
applied to constant values. The presence of inline asm defeats the
compiler though, forcing it to emit extraneous CLZ/DCLZ calculation for
processors that support these instructions.
Use `__builtin_constant_p' then to avoid inline asm altogether for
constants.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9681/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/include/asm/bitops.h b/arch/mips/include/asm/bitops.h
index 9f935f6..0cf29bd 100644
--- a/arch/mips/include/asm/bitops.h
+++ b/arch/mips/include/asm/bitops.h
@@ -481,7 +481,7 @@
{
int num;
- if (BITS_PER_LONG == 32 &&
+ if (BITS_PER_LONG == 32 && !__builtin_constant_p(word) &&
__builtin_constant_p(cpu_has_clo_clz) && cpu_has_clo_clz) {
__asm__(
" .set push \n"
@@ -494,7 +494,7 @@
return 31 - num;
}
- if (BITS_PER_LONG == 64 &&
+ if (BITS_PER_LONG == 64 && !__builtin_constant_p(word) &&
__builtin_constant_p(cpu_has_mips64) && cpu_has_mips64) {
__asm__(
" .set push \n"
@@ -559,7 +559,8 @@
{
int r;
- if (__builtin_constant_p(cpu_has_clo_clz) && cpu_has_clo_clz) {
+ if (!__builtin_constant_p(x) &&
+ __builtin_constant_p(cpu_has_clo_clz) && cpu_has_clo_clz) {
__asm__(
" .set push \n"
" .set "MIPS_ISA_LEVEL" \n"