[Bug target/93453] PPC: rldimi not taken into account to avoid shift+or
guihaoc at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Tue Nov 23 02:46:17 GMT 2021
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93453
--- Comment #6 from HaoChen Gui <guihaoc at gcc dot gnu.org> ---
Sehger,
Yes, I found that the nonzero_bits doesn't return exact value in other pass.
So calling nonzero_bits in md file is bad as it can't be recognized in other
pass.
Right now I want to convert a single pseudo to the pseudo AND with a mask in
combine pass if its nonzero_bits is less than its mode mask and the outer
operation is plus/ior/xor and its one of inner operation is
ashift/lshiftrt/and. Thus it is possible to match rotate and insert pattern.
What's your opinion? Thanks a lot.
(ior:DI (ashift:DI (reg:DI 125)
(const_int 32 [0x20]))
(reg:DI 126)))
is converted to
(ior:DI (ashift:DI (reg:DI 125)
(const_int 32 [0x20]))
(and:DI (reg:DI 126)
(const_int 4294967295 [0xfffffff]))))
patch.diff
diff --git a/gcc/combine.c b/gcc/combine.c
index 892c834a160..8b72a5ec831 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -11539,6 +11539,26 @@ change_zero_ext (rtx pat)
return changed;
}
+/* Convert a psuedo to psuedo AND with a mask if its nonzero_bits is less
+ than its mode mask. */
+static bool
+pseudo_and_with_mask (rtx *reg)
+{
+ bool changed = false;
+ gcc_assert (REG_P (*reg));
+
+ machine_mode mode = GET_MODE (*reg);
+ unsigned HOST_WIDE_INT nonzero = nonzero_bits (*reg, mode);
+ if (nonzero < GET_MODE_MASK (mode))
+ {
+ rtx x = gen_rtx_AND (mode, *reg, GEN_INT (nonzero));
+ SUBST (*reg, x);
+ changed = true;
+ //fprintf (stdout, "PIX optimization\n");
+ }
+ return changed;
+}
+
/* Like recog, but we receive the address of a pointer to a new pattern.
We try to match the rtx that the pointer points to.
If that fails, we may try to modify or replace the pattern,
@@ -11565,9 +11585,34 @@ recog_for_combine (rtx *pnewpat, rtx_insn *insn, rtx
*pnotes)
void *marker = get_undo_marker ();
bool changed = false;
+ //bool PIX_opt = false;
if (GET_CODE (pat) == SET)
- changed = change_zero_ext (pat);
+ {
+ rtx src = SET_SRC (pat);
+ if ((GET_CODE (src) == IOR
+ || GET_CODE (src) == XOR
+ || GET_CODE (src) == PLUS)
+ && (((GET_CODE (XEXP (src, 0)) == ASHIFT
+ || GET_CODE (XEXP (src, 0)) == LSHIFTRT
+ || GET_CODE (XEXP (src, 0)) == AND)
+ && REG_P (XEXP (src, 1)))
+ || ((GET_CODE (XEXP (src, 1)) == ASHIFT
+ || GET_CODE (XEXP (src, 1)) == LSHIFTRT
+ || GET_CODE (XEXP (src, 1)) == AND)
+ && REG_P (XEXP (src, 0)))))
+ {
+ changed = REG_P (XEXP (src, 0))
+ ? pseudo_and_with_mask (&XEXP (SET_SRC (pat), 0))
+ : pseudo_and_with_mask (&XEXP (SET_SRC (pat), 1));
+ if (changed)
+ {
+ maybe_swap_commutative_operands (SET_SRC (pat));
+ //PIX_opt = true;
+ }
+ }
+ changed |= change_zero_ext (pat);
+ }
else if (GET_CODE (pat) == PARALLEL)
{
int i;
@@ -11585,6 +11630,8 @@ recog_for_combine (rtx *pnewpat, rtx_insn *insn, rtx
*pnotes)
if (insn_code_number < 0)
undo_to_marker (marker);
+ //else if (PIX_opt)
+ //fprintf (stdout, "PIX applied\n");
}
return insn_code_number;
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