On Tue, Jun 09, 2015 at 08:09:28PM +0200, Uros Bizjak wrote:
> Please find attach a patch that takes your idea slightly further. We
> find perhaps zero-extended UNSPEC_TP, and copy it for further use. At
> its place, we simply slap const0_rtx. We know that address to
Is that safe? I mean, the address, even if offsetable, can have some
immediate already (seems e.g. the offsettable_memref_p predicate just checks
you can plus_constant some small integer and be recognized again) and if you
turn the %gs: into a const0_rtx, it would fail next decompose.
And when you already have the PLUS which has UNSPEC_TP as one of its
arguments, replacing that PLUS with the other argument is IMHO very easy.
Perhaps you are right that there is no need to copy_rtx, supposedly
the rtx shouldn't be shared with anything and thus can be modified in place.
If -mx32 is a non-issue here, then perhaps my initial patch is good enough?
> Index: config/i386/i386.c
> ===================================================================
> --- config/i386/i386.c (revision 224292)
> +++ config/i386/i386.c (working copy)
> @@ -22858,7 +22858,7 @@ ix86_split_long_move (rtx operands[])
> Do an lea to the last part and use only one colliding move. */
> else if (collisions > 1)
> {
> - rtx base;
> + rtx base, addr, tls_base = NULL_RTX;
>
> collisions = 1;
>
> @@ -22869,10 +22869,52 @@ ix86_split_long_move (rtx operands[])
> if (GET_MODE (base) != Pmode)
> base = gen_rtx_REG (Pmode, REGNO (base));
>
> - emit_insn (gen_rtx_SET (base, XEXP (part[1][0], 0)));
> + addr = XEXP (part[1][0], 0);
> + if (TARGET_TLS_DIRECT_SEG_REFS)
> + {
> + struct ix86_address parts;
> + int ok = ix86_decompose_address (addr, &parts);
> + gcc_assert (ok);
> + if (parts.seg != SEG_DEFAULT)
> + {
> + /* It is not valid to use %gs: or %fs: in
> + lea though, so we need to remove it from the
> + address used for lea and add it to each individual
> + memory loads instead. */
> + rtx *x = &addr;
> + while (GET_CODE (*x) == PLUS)
> + {
> + for (i = 0; i < 2; i++)
> + {
> + rtx op = XEXP (*x, i);
> + if ((GET_CODE (op) == UNSPEC
> + && XINT (op, 1) == UNSPEC_TP)
> + || (GET_CODE (op) == ZERO_EXTEND
> + && GET_CODE (XEXP (op, 0)) == UNSPEC
> + && (XINT (XEXP (op, 0), 1)
> + == UNSPEC_TP)))
> + {
> + tls_base = XEXP (*x, i);
> + XEXP (*x, i) = const0_rtx;
> + break;
> + }
> + }
> +
> + if (tls_base)
> + break;
> + x = &XEXP (*x, 0);
> + }
> + gcc_assert (tls_base);
> + }
> + }
> + emit_insn (gen_rtx_SET (base, addr));
> + if (tls_base)
> + base = gen_rtx_PLUS (GET_MODE (base), base, tls_base);
> part[1][0] = replace_equiv_address (part[1][0], base);
> for (i = 1; i < nparts; i++)
> {
> + if (tls_base)
> + base = copy_rtx (base);
> tmp = plus_constant (Pmode, base, UNITS_PER_WORD * i);
> part[1][i] = replace_equiv_address (part[1][i], tmp);
> }
Jakub
