From 64b6918ea9ab897d6c6bff1ae351ff950519e831 Mon Sep 17 00:00:00 2001
From: Alex Waterman <alexw@nvidia.com>
Date: Tue, 22 May 2018 11:24:22 -0700
Subject: 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>
---
 drivers/gpu/nvgpu/common/posix/bitmap.c | 57 ++-------------------------------
 1 file 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,
-- 
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