Add math.pow2_f{16,32,64}, fast floating point 2^x where x is an integer.

1 files changed, 48 insertions, 1 deletions

diff --git a/core/math/math.odin b/core/math/math.odin
index 4215a8075..a5d86cffb 100644
--- a/core/math/math.odin
+++ b/core/math/math.odin
@@ -203,7 +203,54 @@ pow10_f64 :: proc "contextless" (n: f64) -> f64 {
 	return 0
 }
 
+pow2_f64 :: proc(#any_int exp: int) -> (res: f64) {
+	switch {
+	case exp >= -1022 && exp <= 1023: // Normal
+		return transmute(f64)(u64(exp + F64_BIAS) << F64_SHIFT)
+	case exp < -1075:                 // Underflow
+		return f64(0)
+	case exp == -1075:                // Underflow
+		return 0h00000000_00000001
+	case exp < -1022:                 // Denormal
+		x := u64(exp + (F64_SHIFT + 1) + F64_BIAS) << F64_SHIFT
+		return f64(1) / (1 << (F64_SHIFT + 1)) * transmute(f64)x
+	case exp > 1023:                  // Overflow, +Inf
+		return 0h7ff00000_00000000
+	}
+	unreachable()
+}
 
+pow2_f32 :: proc(#any_int exp: int) -> (res: f32) {
+	switch {
+	case exp >= -126 && exp <= 127:  // Normal
+		return transmute(f32)(u32(exp + F32_BIAS) << F32_SHIFT)
+	case exp < -151:                 // Underflow
+		return f32(0)
+	case exp < -126:                 // Denormal
+		x := u32(exp + (F32_SHIFT + 1) + F32_BIAS) << F32_SHIFT
+		return f32(1) / (1 << (F32_SHIFT + 1)) * transmute(f32)x
+	case exp > 127:                  // Overflow, +Inf
+		return 0h7f80_0000
+	}
+	unreachable()
+}
+
+pow2_f16 :: proc(#any_int exp: int) -> (res: f16) {
+	switch {
+	case exp >= -14 && exp <= 15:    // Normal
+		return transmute(f16)(u16(exp + F16_BIAS) << F16_SHIFT)
+	case exp < -25:                  // Underflow
+		return 0h0000
+	case exp == -25:                 // Underflow
+		return 0h0001
+	case exp < -14:                  // Denormal
+		x := u16(exp + (F16_SHIFT + 1) + F16_BIAS) << F16_SHIFT
+		return f16(1) / (1 << (F16_SHIFT + 1)) * transmute(f16)x
+	case exp > 15:                   // Overflow, +Inf
+		return 0h7c00
+	}
+	unreachable()
+}
 
 @(require_results)
 ldexp_f64 :: proc "contextless" (val: f64, exp: int) -> f64 {
@@ -2302,4 +2349,4 @@ INF_F64     :: f64(0h7FF0_0000_0000_0000)
 NEG_INF_F64 :: f64(0hFFF0_0000_0000_0000)
 
 SNAN_F64    :: f64(0h7FF0_0000_0000_0001)
-QNAN_F64    :: f64(0h7FF8_0000_0000_0001)
+QNAN_F64    :: f64(0h7FF8_0000_0000_0001)
\ No newline at end of file