undefined symbol: ___floatunoitf

[scheibo]

Zig Version

0.14.0-dev.2987+183bb8b08

Steps to Reproduce and Observed Behavior

const std = @import("std");

test "___floatunoitf" {
    var p: u256 = 20;
    p = 21;
    var q: u256 = 41;
    q = 42;
    try std.testing.expectEqual(@as(f128, 50.0), 100 * @as(f128, @floatFromInt(p)) / @as(f128, @floatFromInt(q)));
}

error: undefined symbol: ___floatunoitf
    note: referenced by /Users/kjs/Downloads/.zig-cache/o/734b3cba46dae3cc305996316ca9f311/test.o:_main.test.___floatunoitf
    note: referenced by /Users/kjs/Downloads/.zig-cache/o/734b3cba46dae3cc305996316ca9f311/test.o:_main.test.___floatunoitf

Expected Behavior

Passing test. Switching from u256 -> u128 works.

#15057 appears to be the same issue that was closed for not being able to reproduce, but it definitely reproduces on 0.11.0, 0.12.0, 0.13.0, and master for me.

[Rexicon226]

Here's a bit of a cleaner reproduction that makes the issue more obvious:

test "___floatunoitf" {
    _ = foo(20);
}

fn foo(p: u256) f128 {
    return @floatFromInt(p);
}

[Rexicon226]

The strange o is coming from this code here:

zig/src/target.zig

Lines 677 to 685 in 7d699be

	pub fn compilerRtIntAbbrev(bits: u16) []const u8 {
	return switch (bits) {
	16 => "h",
	32 => "s",
	64 => "d",
	128 => "t",
	else => "o", // Non-standard
	};
	}

LLVM doesn't implement anything with __floatuno* nor do we. I'm not exactly sure where the o comes from.

[Rexicon226]

Some more info:

@floatFromInt with a source integer type above 128 bits in size (unsigned or signed) and with a destination type that's not f128 (so f16, f32, f64) will fail with:

test "bar" {
    _ = foo(20);
}

fn foo(p: u256) f64 {
    return @floatFromInt(p);
}

$ zig test empty.zig -target aarch64-macos
Assertion failed: (LC != RTLIB::UNKNOWN_LIBCALL && "Don't know how to expand this XINT_TO_FP!"), function ExpandIntOp_XINT_TO_FP, file LegalizeIntegerTypes.cpp, line 5574.