Use local frexp

solidpixel · solidpixel · commit 914fb26d6e39 · 2021-02-13T23:00:10.000Z
diff --git a/Source/astcenc_image.cpp b/Source/astcenc_image.cpp
@@ -41,7 +41,7 @@ static float float_to_lns(float p)
 	}
 
 	int expo;
-	float normfrac = frexpf(p, &expo);
+	float normfrac = astc::frexp(p, &expo);
 	float p1;
 	if (expo < -13)
 	{
@@ -56,11 +56,17 @@ static float float_to_lns(float p)
 	}
 
 	if (p1 < 384.0f)
+	{
 		p1 *= 4.0f / 3.0f;
+	}
 	else if (p1 <= 1408.0f)
+	{
 		p1 += 128.0f;
+	}
 	else
+	{
 		p1 = (p1 + 512.0f) * (4.0f / 5.0f);
+	}
 
 	p1 += ((float)expo) * 2048.0f;
 	return p1 + 1.0f;
@@ -72,15 +78,23 @@ static uint16_t lns_to_sf16(uint16_t p)
 	uint16_t ec = p >> 11;
 	uint16_t mt;
 	if (mc < 512)
+	{
 		mt = 3 * mc;
+	}
 	else if (mc < 1536)
+	{
 		mt = 4 * mc - 512;
+	}
 	else
+	{
 		mt = 5 * mc - 2048;
+	}
 
 	uint16_t res = (ec << 10) | (mt >> 3);
 	if (res > 0x7BFF)
+	{
 		res = 0x7BFF;
+	}
 	return res;
 }
 
@@ -91,10 +105,14 @@ static uint16_t lns_to_sf16(uint16_t p)
 uint16_t unorm16_to_sf16(uint16_t p)
 {
 	if (p == 0xFFFF)
+	{
 		return 0x3C00;			// value of 1.0
+	}
 
 	if (p < 4)
+	{
 		return p << 8;
+	}
 
 	int lz = clz32(p) - 16;
 	p <<= (lz + 1);
diff --git a/Source/astcenc_mathlib.h b/Source/astcenc_mathlib.h
@@ -92,6 +92,14 @@
   to future vectorization.
 ============================================================================ */
 
+// Union for manipulation of float bit patterns
+typedef union
+{
+	uint32_t u;
+	int32_t s;
+	float f;
+} if32;
+
 // These are namespaced to avoid colliding with C standard library functions.
 namespace astc
 {
@@ -405,6 +413,23 @@ static inline float sqrt(float v)
 	return std::sqrt(v);
 }
 
+/**
+ * @brief Extract mantissa and exponent of a float value.
+ *
+ * @param      v      The input value.
+ * @param[out] expo   The output exponent.
+ *
+ * @return The mantissa.
+ */
+static inline float frexp(float v, int* expo)
+{
+	if32 p;
+	p.f = v;
+	*expo = ((p.u >> 23) & 0xFF) - 126;
+	p.u = (p.u & 0x807fffff) | 0x3f000000;
+	return p.f;
+}
+
 /**
  * @brief Log base 2, linearized from 2^-14.
  *
@@ -580,13 +605,6 @@ static inline float3 normalize(float3 p) { return p * astc::rsqrt(dot(p, p)); }
 /* ============================================================================
   Softfloat library with fp32 and fp16 conversion functionality.
 ============================================================================ */
-typedef union if32_
-{
-	uint32_t u;
-	int32_t s;
-	float f;
-} if32;
-
 uint32_t clz32(uint32_t p);
 
 /*	sized soft-float types. These are mapped to the sized integer
