From c8ded2f9c940be2d59f5e9dc7d66374b67afba63 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Wed, 20 Oct 2021 16:41:08 -0700
Subject: stage2: implement big int to float conversion

---
 src/value.zig | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

(limited to 'src/value.zig')

diff --git a/src/value.zig b/src/value.zig
index fce5e8afb1..7c24cdab81 100644
--- a/src/value.zig
+++ b/src/value.zig
@@ -1853,17 +1853,26 @@ pub const Value = extern union {
         };
     }
 
-    pub fn intToFloat(val: Value, allocator: *Allocator, dest_ty: Type, target: Target) !Value {
+    pub fn intToFloat(val: Value, arena: *Allocator, dest_ty: Type, target: Target) !Value {
         switch (val.tag()) {
             .undef, .zero, .one => return val,
             .the_only_possible_value => return Value.initTag(.zero), // for i0, u0
             .int_u64 => {
-                return intToFloatInner(val.castTag(.int_u64).?.data, allocator, dest_ty, target);
+                return intToFloatInner(val.castTag(.int_u64).?.data, arena, dest_ty, target);
             },
             .int_i64 => {
-                return intToFloatInner(val.castTag(.int_i64).?.data, allocator, dest_ty, target);
+                return intToFloatInner(val.castTag(.int_i64).?.data, arena, dest_ty, target);
+            },
+            .int_big_positive => {
+                const limbs = val.castTag(.int_big_positive).?.data;
+                const float = bigIntToFloat(limbs, true);
+                return floatToValue(float, arena, dest_ty, target);
+            },
+            .int_big_negative => {
+                const limbs = val.castTag(.int_big_negative).?.data;
+                const float = bigIntToFloat(limbs, false);
+                return floatToValue(float, arena, dest_ty, target);
             },
-            .int_big_positive, .int_big_negative => @panic("big int to float"),
             else => unreachable,
         }
     }
@@ -1878,6 +1887,16 @@ pub const Value = extern union {
         }
     }
 
+    fn floatToValue(float: f128, arena: *Allocator, dest_ty: Type, target: Target) !Value {
+        switch (dest_ty.floatBits(target)) {
+            16 => return Value.Tag.float_16.create(arena, @floatCast(f16, float)),
+            32 => return Value.Tag.float_32.create(arena, @floatCast(f32, float)),
+            64 => return Value.Tag.float_64.create(arena, @floatCast(f64, float)),
+            128 => return Value.Tag.float_128.create(arena, float),
+            else => unreachable,
+        }
+    }
+
     /// Supports both floats and ints; handles undefined.
     pub fn numberAddWrap(
         lhs: Value,
-- 
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