Implement missing f128-related compiler_rt functions

[tiehuis]

See https://github.com/llvm-project/llvm-project-20170507/tree/master/compiler-rt/lib/builtins for a reference.

A tentative list is as follows:

• floatunditf
• floatunsitf
• floatuntitf
• floatuntidf
• floatuntisf
• trunctfdf2
• trunctfsf2
• floattitf
• floattidf
• floattisf

The following example program should compile with no linking errors when complete.

fn check_floatunditf(a: u64) -> f128 { f128(a) }
fn check_floatunsitf(a: u32) -> f128 { f128(a) }
fn check_floatuntitf(a: u128) -> f128 { f128(a) }
fn check_floatuntidf(a: u128) -> f64 { f64(a) }
fn check_floatuntisf(a: u128) -> f32 { f32(a) }
fn check_trunctfdf2(a: f128) -> f64 { f64(a) }
fn check_trunctfsf2(a: f128) -> f32 { f32(a) }
fn check_floattitf(a: i128) -> f128 { f128(a) }
fn check_floattidf(a: i128) -> f64 { f64(a) }
fn check_floattisf(a: i128) -> f32 { f32(a) }

pub fn main() -> %void {
    _ = check_floatunditf(123);
    _ = check_floatunsitf(123);
    _ = check_floatuntitf(1237);
    _ = check_floatuntidf(1237);
    _ = check_floatuntisf(1237);
    _ = check_trunctfdf2(0.4);
    _ = check_trunctfsf2(0.4);
    _ = check_floattitf(123);
    _ = check_floattidf(123);
    _ = check_floattisf(123);
}

[skyfex]

Possible missing built-ins when compiling for ARM with soft-float:

ld.lld: error: undefined symbol: __aeabi_memcpy
>>> referenced by test.zig:70 (C:\SW\zig\zig-nrf-demo\test.zig:70)
>>>               .\zig-cache\test.o:(main)

ld.lld: error: undefined symbol: __aeabi_fmul
>>> referenced by builtin.zig:75
>>>               .\zig-cache\builtin.o:(generic_fmod)

ld.lld: error: undefined symbol: __aeabi_fdiv
>>> referenced by builtin.zig:75
>>>               .\zig-cache\builtin.o:(generic_fmod)

ld.lld: error: undefined symbol: __aeabi_fmul
>>> referenced by builtin.zig:79
>>>               .\zig-cache\builtin.o:(generic_fmod)

ld.lld: error: undefined symbol: __aeabi_fmul
>>> referenced by builtin.zig:106
>>>               .\zig-cache\builtin.o:(generic_fmod)

ld.lld: error: undefined symbol: __aeabi_fmul
>>> referenced by builtin.zig:114
>>>               .\zig-cache\builtin.o:(generic_fmod)

ld.lld: error: undefined symbol: __aeabi_dmul
>>> referenced by builtin.zig:75
>>>               .\zig-cache\builtin.o:(generic_fmod.1)

ld.lld: error: undefined symbol: __aeabi_ddiv
>>> referenced by builtin.zig:75
>>>               .\zig-cache\builtin.o:(generic_fmod.1)

ld.lld: error: undefined symbol: __aeabi_dmul
>>> referenced by builtin.zig:79
>>>               .\zig-cache\builtin.o:(generic_fmod.1)

ld.lld: error: undefined symbol: __aeabi_dmul
>>> referenced by builtin.zig:106
>>>               .\zig-cache\builtin.o:(generic_fmod.1)

ld.lld: error: undefined symbol: __aeabi_dmul
>>> referenced by builtin.zig:114
>>>               .\zig-cache\builtin.o:(generic_fmod.1)

ld.lld: error: undefined symbol: __aeabi_fadd
>>> referenced by floor.zig:45 (C:\SW\zig\lib\zig\std\math\floor.zig:45)
>>>               .\zig-cache\builtin.o:(floor.0)

ld.lld: error: undefined symbol: __aeabi_fadd
>>> referenced by floor.zig:39 (C:\SW\zig\lib\zig\std\math\floor.zig:39)
>>>               .\zig-cache\builtin.o:(floor.0)

ld.lld: error: undefined symbol: __aeabi_fcmpeq
>>> referenced by floor.zig:26 (C:\SW\zig\lib\zig\std\math\floor.zig:26)
>>>               .\zig-cache\builtin.o:(floor.0)

ld.lld: error: undefined symbol: __aeabi_fadd
>>> referenced by ceil.zig:44 (C:\SW\zig\lib\zig\std\math\ceil.zig:44)
>>>               .\zig-cache\builtin.o:(ceil.0)

ld.lld: error: undefined symbol: __aeabi_fadd
>>> referenced by ceil.zig:37 (C:\SW\zig\lib\zig\std\math\ceil.zig:37)
>>>               .\zig-cache\builtin.o:(ceil.0)

ld.lld: error: undefined symbol: __aeabi_fcmpeq
>>> referenced by ceil.zig:26 (C:\SW\zig\lib\zig\std\math\ceil.zig:26)
>>>               .\zig-cache\builtin.o:(ceil.0)

ld.lld: error: undefined symbol: __aeabi_dcmpeq
>>> referenced by floor.zig:59 (C:\SW\zig\lib\zig\std\math\floor.zig:59)
>>>               .\zig-cache\builtin.o:(floor.0.2)

ld.lld: error: undefined symbol: __aeabi_dsub
>>> referenced by floor.zig:65 (C:\SW\zig\lib\zig\std\math\floor.zig:65)
>>>               .\zig-cache\builtin.o:(floor.0.2)

ld.lld: error: undefined symbol: __aeabi_dadd
>>> referenced by floor.zig:65 (C:\SW\zig\lib\zig\std\math\floor.zig:65)
>>>               .\zig-cache\builtin.o:(floor.0.2)

[tiehuis]

Reference code can be found here: https://github.com/llvm-project/llvm-project-20170507/tree/master/compiler-rt/lib/builtins/arm

The arm builtins are all assembly and it would be nice if we could embed the llvm implementations directly with minimal changes. This brings up a question of what the idiomatic way of dealing with architecture specific specializations should be handled. It is likely that choosing the implementation is shifted from the build step (as in C) to a compile-time generative step in Zig. I think #462 would help here.

Also; progress report. I have the main trunc implementations here fairly complete bar some really close inaccuracies (which I suspect are failing due to bad f128 hex literal parsing). Will probably be low on the implementation till January, but expect a partial branch up shortly.

[skyfex]

It seems that __umodsi3 is missing. That should perhaps be prioritized.

[andrewrk]

I implemented #462. You can see examples of how to use it in bootstrap.zig and compiler_rt/index.zig.