stage2: rework `@mulAdd`

 * mul_add AIR instruction: use `pl_op` instead of `ty_pl`. The type is
   always the same as the operand; no need to waste bytes redundantly
   storing the type.
 * AstGen: use coerced_ty for all the operands except for one which we
   use to communicate the type.
 * Sema: use the correct source location for requireRuntimeBlock in
   handling of `@mulAdd`.
 * native backends: handle liveness even for the functions that are
   TODO.
 * C backend: implement `@mulAdd`. It lowers to libc calls.
 * LLVM backend: make `@mulAdd` handle all float types.
   - improved fptrunc and fpext to handle f80 with compiler-rt calls.
 * Value.mulAdd: handle all float types and use the `@mulAdd` builtin.
 * behavior tests: revert the changes to testing `@mulAdd`. These
   changes broke the test coverage, making it only tested at
   compile-time.

Improved f80 support:
 * std.math.fma handles f80
 * move fma functions from freestanding libc to compiler-rt
   - add __fmax and fmal
   - make __fmax and fmaq only exported when they don't alias fmal.
   - make their linkage weak just like the rest of compiler-rt symbols.
 * removed `longDoubleIsF128` and replaced it with `longDoubleIs` which
   takes a type as a parameter. The implementation is now more accurate
   and handles more targets. Similarly, in stage2 the function
   CTypes.sizeInBits is more accurate for long double for more targets.

1 files changed, 17 insertions, 18 deletions

diff --git a/test/behavior/muladd.zig b/test/behavior/muladd.zig
index 4ef0e44acb..53ab6b64ec 100644
--- a/test/behavior/muladd.zig
+++ b/test/behavior/muladd.zig
@@ -2,8 +2,8 @@ const builtin = @import("builtin");
 const expect = @import("std").testing.expect;
 
 test "@mulAdd" {
-    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
@@ -13,22 +13,22 @@ test "@mulAdd" {
 }
 
 fn testMulAdd() !void {
-    if (builtin.zig_backend == .stage1) {
-        const a: f16 = 5.5;
-        const b: f16 = 2.5;
-        const c: f16 = 6.25;
+    {
+        var a: f16 = 5.5;
+        var b: f16 = 2.5;
+        var c: f16 = 6.25;
         try expect(@mulAdd(f16, a, b, c) == 20);
     }
     {
-        const a: f32 = 5.5;
-        const b: f32 = 2.5;
-        const c: f32 = 6.25;
+        var a: f32 = 5.5;
+        var b: f32 = 2.5;
+        var c: f32 = 6.25;
         try expect(@mulAdd(f32, a, b, c) == 20);
     }
     {
-        const a: f64 = 5.5;
-        const b: f64 = 2.5;
-        const c: f64 = 6.25;
+        var a: f64 = 5.5;
+        var b: f64 = 2.5;
+        var c: f64 = 6.25;
         try expect(@mulAdd(f64, a, b, c) == 20);
     }
 }
@@ -39,9 +39,7 @@ test "@mulAdd f80" {
         return error.SkipZigTest;
     }
 
-    // TODO: missing f80 implementation of FMA in `std.math.fma` or compiler-rt
-    // comptime try testMulAdd80();
-
+    comptime try testMulAdd80();
     try testMulAdd80();
 }
 
@@ -53,11 +51,12 @@ fn testMulAdd80() !void {
 }
 
 test "@mulAdd f128" {
-    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
+
     if (builtin.os.tag == .macos and builtin.cpu.arch == .aarch64) {
         // https://github.com/ziglang/zig/issues/9900
         return error.SkipZigTest;
@@ -68,8 +67,8 @@ test "@mulAdd f128" {
 }
 
 fn testMulAdd128() !void {
-    const a: f16 = 5.5;
-    const b: f128 = 2.5;
-    const c: f128 = 6.25;
+    var a: f16 = 5.5;
+    var b: f128 = 2.5;
+    var c: f128 = 6.25;
     try expect(@mulAdd(f128, a, b, c) == 20);
 }