Sema: clean up zirUnaryMath

* pass air_tag instead of zir_tag
 * also pass eval function so that the branch only happens once and the
   body of zirUnaryMath is simplified
 * Value.sqrt: update to handle f80 and f128 in the normalized way that
   includes handling c_longdouble.

Semi-related change: fix incorrect sqrt builtin name for f80 in stage1.

src/value.zig

@@ -3265,24 +3265,34 @@ pub const Value = extern union {
         }
     }
 
-    pub fn sqrt(val: Value, float_type: Type, arena: Allocator) !Value {
-        switch (float_type.tag()) {
-            .f16 => {
+    pub fn sqrt(val: Value, float_type: Type, arena: Allocator, target: Target) Allocator.Error!Value {
+        switch (float_type.floatBits(target)) {
+            16 => {
                 const f = val.toFloat(f16);
                 return Value.Tag.float_16.create(arena, @sqrt(f));
             },
-            .f32 => {
+            32 => {
                 const f = val.toFloat(f32);
                 return Value.Tag.float_32.create(arena, @sqrt(f));
             },
-            .f64 => {
+            64 => {
                 const f = val.toFloat(f64);
                 return Value.Tag.float_64.create(arena, @sqrt(f));
             },
-
-            // TODO: implement @sqrt for these types
-            .f128, .comptime_float, .c_longdouble => unreachable,
-
+            80 => {
+                if (true) {
+                    @panic("TODO implement compiler_rt __sqrtx");
+                }
+                const f = val.toFloat(f80);
+                return Value.Tag.float_80.create(arena, @sqrt(f));
+            },
+            128 => {
+                if (true) {
+                    @panic("TODO implement compiler_rt sqrtq");
+                }
+                const f = val.toFloat(f128);
+                return Value.Tag.float_128.create(arena, @sqrt(f));
+            },
             else => unreachable,
         }
     }