From 716d6a026f468cdb6b84a3e7f1004904b9ac6ecc Mon Sep 17 00:00:00 2001
From: Jacob Young <jacobly0@users.noreply.github.com>
Date: Wed, 10 May 2023 13:20:13 -0400
Subject: std: revert `comptime_float` support

Removed since I'm aware of some design considerations of `comptime_float`.
---
 lib/std/math/float.zig | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

(limited to 'lib/std/math/float.zig')

diff --git a/lib/std/math/float.zig b/lib/std/math/float.zig
index 134277b91d..768cc03285 100644
--- a/lib/std/math/float.zig
+++ b/lib/std/math/float.zig
@@ -4,29 +4,21 @@ const expect = std.testing.expect;
 
 /// Creates a raw "1.0" mantissa for floating point type T. Used to dedupe f80 logic.
 inline fn mantissaOne(comptime T: type) comptime_int {
-    return 1 << floatFractionalBits(T) & ((1 << floatMantissaBits(T)) - 1);
+    return if (@typeInfo(T).Float.bits == 80) 1 << floatFractionalBits(T) else 0;
 }
 
 /// Creates floating point type T from an unbiased exponent and raw mantissa.
 inline fn reconstructFloat(comptime T: type, comptime exponent: comptime_int, comptime mantissa: comptime_int) T {
-    const FBits = @Type(.{ .Float = .{ .bits = floatBits(T) } });
-    const TBits = @Type(.{ .Int = .{ .signedness = .unsigned, .bits = floatBits(T) } });
+    const TBits = @Type(.{ .Int = .{ .signedness = .unsigned, .bits = @bitSizeOf(T) } });
     const biased_exponent = @as(TBits, exponent + floatExponentMax(T));
-    return @bitCast(FBits, (biased_exponent << floatMantissaBits(T)) | @as(TBits, mantissa));
-}
-
-/// Returns the number of bits in floating point type T.
-pub inline fn floatBits(comptime T: type) comptime_int {
-    return switch (@typeInfo(T)) {
-        .Float => |info| info.bits,
-        .ComptimeFloat => 128,
-        else => @compileError(@typeName(T) ++ " is not a floating point type"),
-    };
+    return @bitCast(T, (biased_exponent << floatMantissaBits(T)) | @as(TBits, mantissa));
 }
 
 /// Returns the number of bits in the exponent of floating point type T.
 pub inline fn floatExponentBits(comptime T: type) comptime_int {
-    return switch (floatBits(T)) {
+    comptime assert(@typeInfo(T) == .Float);
+
+    return switch (@typeInfo(T).Float.bits) {
         16 => 5,
         32 => 8,
         64 => 11,
@@ -38,7 +30,9 @@ pub inline fn floatExponentBits(comptime T: type) comptime_int {
 
 /// Returns the number of bits in the mantissa of floating point type T.
 pub inline fn floatMantissaBits(comptime T: type) comptime_int {
-    return switch (floatBits(T)) {
+    comptime assert(@typeInfo(T) == .Float);
+
+    return switch (@typeInfo(T).Float.bits) {
         16 => 10,
         32 => 23,
         64 => 52,
@@ -50,10 +44,12 @@ pub inline fn floatMantissaBits(comptime T: type) comptime_int {
 
 /// Returns the number of fractional bits in the mantissa of floating point type T.
 pub inline fn floatFractionalBits(comptime T: type) comptime_int {
+    comptime assert(@typeInfo(T) == .Float);
+
     // standard IEEE floats have an implicit 0.m or 1.m integer part
     // f80 is special and has an explicitly stored bit in the MSB
     // this function corresponds to `MANT_DIG - 1' from C
-    return switch (floatBits(T)) {
+    return switch (@typeInfo(T).Float.bits) {
         16 => 10,
         32 => 23,
         64 => 52,
@@ -105,7 +101,6 @@ test "float bits" {
     inline for ([_]type{ f16, f32, f64, f80, f128, c_longdouble }) |T| {
         // (1 +) for the sign bit, since it is separate from the other bits
         const size = 1 + floatExponentBits(T) + floatMantissaBits(T);
-        try expect(floatBits(T) == size);
         try expect(@bitSizeOf(T) == size);
 
         // for machine epsilon, assert expmin <= -prec <= expmax
-- 
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