[Bug target/93453] PPC: rldimi not taken into account to avoid shift+or

["guihaoc at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93453

--- Comment #8 from HaoChen Gui <guihaoc at gcc dot gnu.org> ---
I refined the patch and put all things in a helper - change_pseudo_and_mask. As
you mentioned, it's still a band-aid. The perfect solution might be a better
version of nonzero_bits. Thanks.

diff --git a/gcc/combine.c b/gcc/combine.c
index 892c834a160..f0e6ca5d8cf 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -11539,6 +11539,41 @@ 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
+change_pseudo_and_mask (rtx pat)
+{
+  bool changed = false;
+
+  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)))))
+    {
+      rtx *reg = REG_P (XEXP (src, 0))
+                ? &XEXP (SET_SRC (pat), 0)
+                : &XEXP (SET_SRC (pat), 1);
+      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;
+       }
+     }
+  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 +11600,18 @@ 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);
+    {
+      changed = change_pseudo_and_mask (pat);
+      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 +11629,8 @@ 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;