From 30ef0336932cb2ec866a082b9b4584d08d179a55 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Fri, 17 Jun 2022 19:25:06 -0700
Subject: [PATCH] compiler-rt: fix logic for choosing `__gnu_{f2h,h2f}_ieee`

wasm32-wasi-musl wants the standard symbol names however Linux requires
the `__gnu_*` flavors. I did not find any authoritative source on what
decides which symbol flavors to use. If we run into more trouble in the
future we can go back to having both.
---
 lib/compiler_rt/common.zig      | 37 ++++++++++++++++++++++++++-------
 lib/compiler_rt/extendhfsf2.zig |  2 +-
 lib/compiler_rt/truncsfhf2.zig  |  2 +-
 3 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/lib/compiler_rt/common.zig b/lib/compiler_rt/common.zig
index 6dc6ced926..8f9253b44b 100644
--- a/lib/compiler_rt/common.zig
+++ b/lib/compiler_rt/common.zig
@@ -1,7 +1,5 @@
 const std = @import("std");
 const builtin = @import("builtin");
-const math = std.math;
-const is_test = builtin.is_test;
 
 pub const linkage: std.builtin.GlobalLinkage = if (builtin.is_test) .Internal else .Weak;
 pub const want_aeabi = switch (builtin.abi) {
@@ -18,19 +16,44 @@ pub const want_aeabi = switch (builtin.abi) {
     else => false,
 };
 pub const want_ppc_abi = builtin.cpu.arch.isPPC() or builtin.cpu.arch.isPPC64();
-pub const want_msvc_abi = builtin.abi == .msvc;
-/// Example symbols:
+
+/// This governs whether to use these symbol names for f16/f32 conversions
+/// rather than the standard names:
 /// * __gnu_f2h_ieee
 /// * __gnu_h2f_ieee
-pub const want_gnu_abi = builtin.abi.isGnu() or builtin.abi.isMusl();
+/// Known correct configurations:
+///   x86_64-freestanding-none => true
+///   x86_64-linux-none => true
+///   x86_64-linux-gnu => true
+///   x86_64-linux-musl => true
+///   x86_64-linux-eabi => true
+///   arm-linux-musleabihf => true
+///   arm-linux-gnueabihf => true
+///   arm-linux-eabihf => false
+///   wasm32-wasi-musl => false
+///   wasm32-freestanding-none => false
+///   x86_64-windows-gnu => true
+///   x86_64-windows-msvc => true
+///   any-macos-any => doesn't matter; libSystem has both symbol flavors
+pub const gnu_f16_abi = switch (builtin.cpu.arch) {
+    .wasm32, .wasm64 => false,
+
+    .arm, .armeb, .thumb, .thumbeb => switch (builtin.abi) {
+        .eabi, .eabihf => false,
+        else => true,
+    },
+
+    else => true,
+};
+
 pub const want_sparc_abi = builtin.cpu.arch.isSPARC();
 
 // Avoid dragging in the runtime safety mechanisms into this .o file,
 // unless we're trying to test compiler-rt.
 pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace) noreturn {
     _ = error_return_trace;
-    @setCold(true);
-    if (is_test) {
+    if (builtin.is_test) {
+        @setCold(true);
         std.debug.panic("{s}", .{msg});
     } else {
         unreachable;
diff --git a/lib/compiler_rt/extendhfsf2.zig b/lib/compiler_rt/extendhfsf2.zig
index 56e6b9c01b..a6bf5f5be5 100644
--- a/lib/compiler_rt/extendhfsf2.zig
+++ b/lib/compiler_rt/extendhfsf2.zig
@@ -4,7 +4,7 @@ const extendf = @import("./extendf.zig").extendf;
 pub const panic = common.panic;
 
 comptime {
-    if (common.want_gnu_abi) {
+    if (common.gnu_f16_abi) {
         @export(__gnu_h2f_ieee, .{ .name = "__gnu_h2f_ieee", .linkage = common.linkage });
     } else if (common.want_aeabi) {
         @export(__aeabi_h2f, .{ .name = "__aeabi_h2f", .linkage = common.linkage });
diff --git a/lib/compiler_rt/truncsfhf2.zig b/lib/compiler_rt/truncsfhf2.zig
index 329b3332a2..489fb8658d 100644
--- a/lib/compiler_rt/truncsfhf2.zig
+++ b/lib/compiler_rt/truncsfhf2.zig
@@ -4,7 +4,7 @@ const truncf = @import("./truncf.zig").truncf;
 pub const panic = common.panic;
 
 comptime {
-    if (common.want_gnu_abi) {
+    if (common.gnu_f16_abi) {
         @export(__gnu_f2h_ieee, .{ .name = "__gnu_f2h_ieee", .linkage = common.linkage });
     } else if (common.want_aeabi) {
         @export(__aeabi_f2h, .{ .name = "__aeabi_f2h", .linkage = common.linkage });