Switch to Mesa-style 24-bit float packing.

Seems like Mesa's got it right, so we should follow suit.

2 files changed, 28 insertions, 41 deletions

diff --git a/src/radeon_textured_video.c b/src/radeon_textured_video.c
index 8fc380e1..c7d06202 100644
--- a/src/radeon_textured_video.c
+++ b/src/radeon_textured_video.c
@@ -80,6 +80,32 @@ static __inline__ uint32_t F_TO_DW(float val)
     return tmp.l;
 }
 
+/* Borrowed from Mesa */
+static __inline__ uint32_t F_TO_24(float val)
+{
+	float mantissa;
+	int exponent;
+	uint32_t float24 = 0;
+
+	if (val == 0.0)
+		return 0;
+
+	mantissa = frexpf(val, &exponent);
+
+	/* Handle -ve */
+	if (mantissa < 0) {
+		float24 |= (1 << 23);
+		mantissa = mantissa * -1.0;
+	}
+	/* Handle exponent, bias of 63 */
+	exponent += 62;
+	float24 |= (exponent << 16);
+	/* Kill 7 LSB of mantissa */
+	float24 |= (F_TO_DW(mantissa) & 0x7FFFFF) >> 7;
+
+	return float24;
+}
+
 #define ACCEL_MMIO
 #define ACCEL_PREAMBLE()	unsigned char *RADEONMMIO = info->MMIO
 #define BEGIN_ACCEL(n)		RADEONWaitForFifo(pScrn, (n))
diff --git a/src/radeon_textured_videofuncs.c b/src/radeon_textured_videofuncs.c
index 8fb87981..8c90f418 100644
--- a/src/radeon_textured_videofuncs.c
+++ b/src/radeon_textured_videofuncs.c
@@ -90,45 +90,6 @@ do {								\
 
 #endif /* !ACCEL_CP */
 
-#ifndef __FLOAT_TO_S16E7__
-#define __FLOAT_TO_S16E7__
-
-static int float_to_s16e7(float in)
-{
-	union {
-		float f;
-		int i;
-	} x;
-
-	int s, e, f, out; // sign, exponent, fraction
-
-	x.f = in;
-	s = (x.i & (1 << 31)) >> 31;
-	e = (x.i & 0x7f800000) >> 23;
-	f = (x.i & 0x007fffff);
-
-	/* unbias the exponent */
-	e = e - 127;
-	if (e < -63)
-		e = -63;
-	else if (e > 63)
-		e = 63;
-
-	e += 63;
-
-	/* prepend implicit 1 to fraction */
-	f |= (1 << 23);
-	/* cut mantissa to 16 bits */
-	f = (f & 0xffff80) >> 8;
-
-	out = s;
-	out = (out << 7) | e;
-	out = (out << 16) | f;
-
-	return out;
-}
-#endif
-
 static void
 FUNC_NAME(RADEONDisplayTexturedVideo)(ScrnInfoPtr pScrn, RADEONPortPrivPtr pPriv)
 {
@@ -710,13 +671,13 @@ FUNC_NAME(RADEONDisplayTexturedVideo)(ScrnInfoPtr pScrn, RADEONPortPrivPtr pPriv
 						   R300_ALU_ALPHA_OMASK(R300_ALU_ALPHA_MASK_A)));
 
 		/* Shader constants. */
-		OUT_ACCEL_REG(R300_US_ALU_CONST_R(0), float_to_s16e7(1.0/(float)pPriv->w));
+		OUT_ACCEL_REG(R300_US_ALU_CONST_R(0), F_TO_24(1.0/(float)pPriv->w));
 		OUT_ACCEL_REG(R300_US_ALU_CONST_G(0), 0);
 		OUT_ACCEL_REG(R300_US_ALU_CONST_B(0), 0);
 		OUT_ACCEL_REG(R300_US_ALU_CONST_A(0), 0);
 
 		OUT_ACCEL_REG(R300_US_ALU_CONST_R(1), 0);
-		OUT_ACCEL_REG(R300_US_ALU_CONST_G(1), float_to_s16e7(1.0/(float)pPriv->h));
+		OUT_ACCEL_REG(R300_US_ALU_CONST_G(1), F_TO_24(1.0/(float)pPriv->h));
 		OUT_ACCEL_REG(R300_US_ALU_CONST_B(1), 0);
 		OUT_ACCEL_REG(R300_US_ALU_CONST_A(1), 0);