| Issue |
98126
|
| Summary |
PowerPC `fp128` -> `half` uses `__trunctfhf2` but should be `__trunckfhf2`
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
tgross35
|
```llvm
define half @trunckfhf(fp128 %a) unnamed_addr {
start:
%_0 = fptrunc fp128 %a to half
ret half %_0
}
```
Output on `powerpc64-unknown-linux-gnu`:
```asm
trunckfhf: # @trunckfhf
.quad .Lfunc_begin0
.quad .TOC.@tocbase
.quad 0
.Lfunc_begin0:
mflr 0
stdu 1, -112(1)
std 0, 128(1)
bl __trunctfhf2
nop
clrldi 3, 3, 48
bl __gnu_h2f_ieee
nop
addi 1, 1, 112
ld 0, 16(1)
mtlr 0
blr
.long 0
.quad 0
```
Note that this emits `__trunctfhf2`. According to https://gcc.gnu.org/wiki/Ieee128PowerPC (second table in section 2.2), `tf` is for whatever `long double` is in C, which on PPC is usually IBM double double, but `kf` is always for IEEE `binary128`. So it seems like this should instead emit a symbol named `__trunckfhf2`.
This would be consistent with other fptrunc operations for `fp128`, which lower to `kf` symbols (`__trunckfsf2`, `__trunckfdf2`).
There is more discussion at this thread https://github.com/llvm/llvm-project/issues/92866. Neither GCC nor LLVM provide this symbol yet in libgcc/compiler-rt, but I don't think that should block correcting the symbol name.
Tested at compiler explorer using `19.0.0git`. Link: https://llvm.godbolt.org/z/7MosczYcr
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