On 6/3/25 11:11 AM, 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?
Jeff, Eric: any thoughts about this?
The thing is it's a clobber. So late-combine's behavior seems sensible
given the dataflow from insn 9. I think we've always interpreted the
clobber list as precisely that -- any incoming value is potentially
destroyed and we have no knowledge of the outgoing value.
That would in turn mean that insn 27 is (effectively) an uninitialized
read.
Jeff
