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"H.J. Lu" <hjl.tools@gmail.com> writes:I added this code for a reason probably to solve some target problems.LRA has
if (REG_P (reg) && (ep = get_elimination (reg)) != NULL) { rtx to_rtx = replace_p ? ep->to_rtx : ep->from_rtx;
if (! replace_p) { offset += (ep->offset - ep->previous_offset); offset = trunc_int_for_mode (offset, GET_MODE (plus_cst_src)); }
if (GET_CODE (XEXP (plus_cst_src, 0)) == SUBREG) to_rtx = gen_lowpart (GET_MODE (XEXP (plus_cst_src, 0)), to_rtx);
Reload has
rtx to_rtx = ep->to_rtx; offset += ep->offset; offset = trunc_int_for_mode (offset, GET_MODE (plus_cst_src));
if (GET_CODE (XEXP (plus_cst_src, 0)) == SUBREG) to_rtx = gen_lowpart (GET_MODE (XEXP (plus_cst_src, 0)), to_rtx);
(gdb) call debug_rtx (ep->to_rtx) (reg/f:DI 7 sp) (gdb) call debug_rtx (ep->from_rtx) (reg/f:DI 16 argp) (gdb)
gen_lowpart returns (reg/f:DI 7 sp) for reload and (reg:SI 16 argp) for LRA. They are caused by
if (FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM /* We should convert arg register in LRA after the elimination if it is possible. */ && xregno == ARG_POINTER_REGNUM && ! lra_in_progress) return -1;
It doesn't work in this case.
This testcase shows that LRA can't convert arg register after the elimination.
Here is a patch to remove ra_in_progress check for ARG_POINTER_REGNUM. Tested on Linux.x86-64. OK to install?Thanks HJ. This looks good to me. As well as your testcase, I think it would be dangerous to reduce this kind of subreg during non-final elimination in cases where the argument pointer occupies more than one hard register (like avr IIRC). We could end up with something like ARG_POINTER_REGNUM+1, which wouldn't show up as an elimination register during the rest of LRA.
It's important that we do get rid of the subreg during the final elimination stage, but I think alter_subreg already handles that case.
Since this code is outside the LRA files: patch is OK if Vlad agrees.
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