gpu: nvgpu: posix: Use GCC builtins for ffs(), fls()

These intrinsics will be fast for the given platform that the
compiler is targeting. This also reduces complexity in the
code.

Change-Id: I6cfb761d6f881056446fa9a5de53dca50ed93c34
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1727383
Reviewed-by: Konsta Holtta <kholtta@nvidia.com>
Reviewed-by: Richard Zhao <rizhao@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

1 files changed, 2 insertions, 55 deletions

diff --git a/drivers/gpu/nvgpu/common/posix/bitmap.c b/drivers/gpu/nvgpu/common/posix/bitmap.c
index 51361777..b45838df 100644
--- a/drivers/gpu/nvgpu/common/posix/bitmap.c
+++ b/drivers/gpu/nvgpu/common/posix/bitmap.c
@@ -31,65 +31,12 @@
 
 unsigned long __nvgpu_posix_fls(unsigned long word)
 {
-        int num = BITS_PER_LONG - 1;
-
-#if BITS_PER_LONG == 64
-        if (!(word & (~0ul << 32))) {
-                num -= 32;
-                word <<= 32;
-        }
-#endif
-        if (!(word & (~0ul << (BITS_PER_LONG-16)))) {
-                num -= 16;
-                word <<= 16;
-        }
-        if (!(word & (~0ul << (BITS_PER_LONG-8)))) {
-                num -= 8;
-                word <<= 8;
-        }
-        if (!(word & (~0ul << (BITS_PER_LONG-4)))) {
-                num -= 4;
-                word <<= 4;
-        }
-        if (!(word & (~0ul << (BITS_PER_LONG-2)))) {
-                num -= 2;
-                word <<= 2;
-        }
-        if (!(word & (~0ul << (BITS_PER_LONG-1))))
-                num -= 1;
-        return num;
+        return __builtin_clzl(word);
 }
 
 unsigned long __nvgpu_posix_ffs(unsigned long word)
 {
-        int num = 0;
-
-#if BITS_PER_LONG == 64
-        if ((word & 0xffffffff) == 0) {
-                num += 32;
-                word >>= 32;
-        }
-#endif
-        if ((word & 0xffff) == 0) {
-                num += 16;
-                word >>= 16;
-        }
-        if ((word & 0xff) == 0) {
-                num += 8;
-                word >>= 8;
-        }
-        if ((word & 0xf) == 0) {
-                num += 4;
-                word >>= 4;
-        }
-        if ((word & 0x3) == 0) {
-                num += 2;
-                word >>= 2;
-        }
-        if ((word & 0x1) == 0)
-                num += 1;
-
-        return num;
+        return __builtin_ffsl(word);
 }
 
 static unsigned long __find_next_bit(const unsigned long *addr,