Use clz ^ 31 instead of 31 - clz; better codegen for GCC
diff --git a/lib/common/bitstream.h b/lib/common/bitstream.h
index 306e019..1c294b8 100644
--- a/lib/common/bitstream.h
+++ b/lib/common/bitstream.h
@@ -164,7 +164,7 @@
_BitScanReverse ( &r, val );
return (unsigned) r;
# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
- return 31 - __builtin_clz (val);
+ return __builtin_clz (val) ^ 31;
# elif defined(__ICCARM__) /* IAR Intrinsic */
return 31 - __CLZ(val);
# else /* Software version */
diff --git a/lib/legacy/zstd_v01.c b/lib/legacy/zstd_v01.c
index ae8cba2..8112527 100644
--- a/lib/legacy/zstd_v01.c
+++ b/lib/legacy/zstd_v01.c
@@ -346,7 +346,7 @@
_BitScanReverse ( &r, val );
return (unsigned) r;
# elif defined(__GNUC__) && (GCC_VERSION >= 304) /* GCC Intrinsic */
- return 31 - __builtin_clz (val);
+ return __builtin_clz (val) ^ 31;
# else /* Software version */
static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;
diff --git a/lib/legacy/zstd_v02.c b/lib/legacy/zstd_v02.c
index de0a4bd..c878379 100644
--- a/lib/legacy/zstd_v02.c
+++ b/lib/legacy/zstd_v02.c
@@ -353,7 +353,7 @@
_BitScanReverse ( &r, val );
return (unsigned) r;
# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
- return 31 - __builtin_clz (val);
+ return __builtin_clz (val) ^ 31;
# else /* Software version */
static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;
diff --git a/lib/legacy/zstd_v03.c b/lib/legacy/zstd_v03.c
index dbc83f1..162bd63 100644
--- a/lib/legacy/zstd_v03.c
+++ b/lib/legacy/zstd_v03.c
@@ -356,7 +356,7 @@
_BitScanReverse ( &r, val );
return (unsigned) r;
# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
- return 31 - __builtin_clz (val);
+ return __builtin_clz (val) ^ 31;
# else /* Software version */
static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;
diff --git a/lib/legacy/zstd_v04.c b/lib/legacy/zstd_v04.c
index 201ce2b..4dec308 100644
--- a/lib/legacy/zstd_v04.c
+++ b/lib/legacy/zstd_v04.c
@@ -627,7 +627,7 @@
_BitScanReverse ( &r, val );
return (unsigned) r;
# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
- return 31 - __builtin_clz (val);
+ return __builtin_clz (val) ^ 31;
# else /* Software version */
static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;
diff --git a/lib/legacy/zstd_v05.c b/lib/legacy/zstd_v05.c
index e347b00..570e0ff 100644
--- a/lib/legacy/zstd_v05.c
+++ b/lib/legacy/zstd_v05.c
@@ -756,7 +756,7 @@
_BitScanReverse ( &r, val );
return (unsigned) r;
# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
- return 31 - __builtin_clz (val);
+ return __builtin_clz (val) ^ 31;
# else /* Software version */
static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;
diff --git a/lib/legacy/zstd_v06.c b/lib/legacy/zstd_v06.c
index f907a3a..2a08e8d 100644
--- a/lib/legacy/zstd_v06.c
+++ b/lib/legacy/zstd_v06.c
@@ -860,7 +860,7 @@
_BitScanReverse ( &r, val );
return (unsigned) r;
# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
- return 31 - __builtin_clz (val);
+ return __builtin_clz (val) ^ 31;
# else /* Software version */
static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;
diff --git a/lib/legacy/zstd_v07.c b/lib/legacy/zstd_v07.c
index a83ddc9..a2eeff8 100644
--- a/lib/legacy/zstd_v07.c
+++ b/lib/legacy/zstd_v07.c
@@ -530,7 +530,7 @@
_BitScanReverse ( &r, val );
return (unsigned) r;
# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
- return 31 - __builtin_clz (val);
+ return __builtin_clz (val) ^ 31;
# else /* Software version */
static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
U32 v = val;