summaryrefslogtreecommitdiffstats
path: root/src
diff options
context:
space:
mode:
authorIlia Mirkin <imirkin@alum.mit.edu>2014-04-25 18:07:41 -0400
committerIlia Mirkin <imirkin@alum.mit.edu>2014-04-28 19:05:07 -0400
commitab4927f3e04918fd8a53c2d91be4dfc65fe9782d (patch)
tree7a18fd31be8bac5ee7136772fee92c6e4be7fac4 /src
parent3e73bf2724596330d71e1ee0548d48b741d3d261 (diff)
gallium/util: add helpers for bitfield manipulation
Add bitwise reversing and signed MSB helpers for software implementation of the new TGSI opcodes. Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu> Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Diffstat (limited to 'src')
-rw-r--r--src/gallium/auxiliary/util/u_math.h31
1 files changed, 31 insertions, 0 deletions
diff --git a/src/gallium/auxiliary/util/u_math.h b/src/gallium/auxiliary/util/u_math.h
index ec03e4e5886..a60e1830a72 100644
--- a/src/gallium/auxiliary/util/u_math.h
+++ b/src/gallium/auxiliary/util/u_math.h
@@ -567,6 +567,22 @@ static INLINE unsigned util_last_bit(unsigned u)
#endif
}
+/**
+ * Find last bit in a word that does not match the sign bit. The least
+ * significant bit is 1.
+ * Return 0 if no bits are set.
+ */
+static INLINE unsigned util_last_bit_signed(int i)
+{
+#if defined(__GNUC__) && ((__GNUC__ * 100 + __GNUC_MINOR__) >= 407)
+ return 31 - __builtin_clrsb(i);
+#else
+ if (i >= 0)
+ return util_last_bit(i);
+ else
+ return util_last_bit(~(unsigned)i);
+#endif
+}
/* Destructively loop over all of the bits in a mask as in:
*
@@ -715,6 +731,21 @@ util_bitcount(unsigned n)
#endif
}
+/**
+ * Reverse bits in n
+ * Algorithm taken from:
+ * http://stackoverflow.com/questions/9144800/c-reverse-bits-in-unsigned-integer
+ */
+static INLINE unsigned
+util_bitreverse(unsigned n)
+{
+ n = ((n >> 1) & 0x55555555u) | ((n & 0x55555555u) << 1);
+ n = ((n >> 2) & 0x33333333u) | ((n & 0x33333333u) << 2);
+ n = ((n >> 4) & 0x0f0f0f0fu) | ((n & 0x0f0f0f0fu) << 4);
+ n = ((n >> 8) & 0x00ff00ffu) | ((n & 0x00ff00ffu) << 8);
+ n = ((n >> 16) & 0xffffu) | ((n & 0xffffu) << 16);
+ return n;
+}
/**
* Convert from little endian to CPU byte order.