On 6/3/25 10:11, Richard Sandiford wrote:
> Vineet Gupta <vine...@rivosinc.com> writes:
>> On 6/3/25 08:24, Richard Sandiford wrote:
>>> I think the issue is that:
>>>
>>> (insn 9 8 27 2 (parallel [
>>> (asm_operands/v ("fsrm %0") ("") 0 [
>>> (reg:SI 15 a5 [139])
>>> ]
>>> [
>>> (asm_input:SI ("r") frm-run-1.c:33)
>>> ]
>>> [] frm-run-1.c:33)
>>> (clobber (reg:V4096QI 69 frm))
>>> ]) "frm-run-1.c":33:3 -1
>>> (nil))
>>>
>>> is seen as invalidating FRM and so:
>>>
>>> (insn 27 9 28 2 (set (reg:SI 15 a5 [144])
>>> (reg:SI 69 frm)) "frm-run-1.c":43:1 2829 {frrmsi}
>>> (nil))
>>>
>>> is seen as an uninitialised read. I suppose clobbers in inline asms
>>> need to be treated as real definitions rather than just kills.
>> In general or specifically inside of late_combine ?
> We can start with the routines that rtl-ssa uses for its dataflow analysis.
> Does the patch below help?
Sorry, it doesn't. It seems the new code is not getting hit because @has_asm is
false.
I tried a little hack to force it for my use case but it doesn't doesn't hit the
new code.
@@ -2236,7 +2236,7 @@ rtx_properties::try_to_add_src (const_rtx x, unsigned int
flags)
}
else if (code == UNSPEC_VOLATILE)
has_volatile_refs = true;
- else if (code == ASM_INPUT || code == ASM_OPERANDS)
+ else if (code == ASM_INPUT || code == ASM_OPERANDS || code == CLOBBER)
Next I tried another mindless hack
@@ -2295,7 +2295,7 @@ rtx_properties::try_to_add_pattern (const_rtx pat)
case CLOBBER:
{
rtx x = XEXP (pat, 0);
- if (has_asm && asm_clobber_is_read_modify_write_p (x))
+ if (asm_clobber_is_read_modify_write_p (x))
Now the new code hits, but the final outcome is still the same, late_combine2 is
still eliminating those.
Thx,
-Vineet
