identify lfs prefixed case PR95347

The same problem also arises for plfs where prefixed_load_p()
doesn't recognize it so we get just lfs in the asm output
with an @pcrel address.

	Backport from master
	2020-06-03  Aaron Sawdey  <acsawdey@linux.ibm.com>

	PR target/95347
	* config/rs6000/rs6000.c (is_stfs_insn): Rename to
	is_lfs_stfs_insn and make it recognize lfs as well.
	(prefixed_store_p): Use is_lfs_stfs_insn().
	(prefixed_load_p): Use is_lfs_stfs_insn() to recognize lfs.

gcc/config/rs6000/rs6000.c

@@ -24978,14 +24978,18 @@ address_to_insn_form (rtx addr,
   return INSN_FORM_BAD;
 }
 
-/* Helper function to see if we're potentially looking at stfs.
+/* Helper function to see if we're potentially looking at lfs/stfs.
    - PARALLEL containing a SET and a CLOBBER
+   - stfs:
     - SET is from UNSPEC_SI_FROM_SF to MEM:SI
     - CLOBBER is a V4SF
+   - lfs:
+    - SET is from UNSPEC_SF_FROM_SI to REG:SF
+    - CLOBBER is a DI
  */
 
 static bool
-is_stfs_insn (rtx_insn *insn)
+is_lfs_stfs_insn (rtx_insn *insn)
 {
   rtx pattern = PATTERN (insn);
   if (GET_CODE (pattern) != PARALLEL)
@@ -25011,16 +25015,22 @@ is_stfs_insn (rtx_insn *insn)
   rtx src = SET_SRC (set);
   rtx scratch = SET_DEST (clobber);
 
-  if (GET_CODE (src) != UNSPEC || XINT (src, 1) != UNSPEC_SI_FROM_SF)
+  if (GET_CODE (src) != UNSPEC)
     return false;
 
-  if (GET_CODE (dest) != MEM || GET_MODE (dest) != SImode)
-    return false;
-
-  if (GET_CODE (scratch) != SCRATCH || GET_MODE (scratch) != V4SFmode)
-    return false;
+  /* stfs case.  */
+  if (XINT (src, 1) == UNSPEC_SI_FROM_SF
+      && GET_CODE (dest) == MEM && GET_MODE (dest) == SImode
+      && GET_CODE (scratch) == SCRATCH && GET_MODE (scratch) == V4SFmode)
+    return true;
 
+  /* lfs case.  */
+  if (XINT (src, 1) == UNSPEC_SF_FROM_SI
+      && GET_CODE (dest) == REG && GET_MODE (dest) == SFmode
+      && GET_CODE (scratch) == SCRATCH && GET_MODE (scratch) == DImode)
     return true;
+
+  return false;
 }
 
 /* Helper function to take a REG and a MODE and turn it into the non-prefixed
@@ -25133,6 +25143,9 @@ prefixed_load_p (rtx_insn *insn)
   else
     non_prefixed = reg_to_non_prefixed (reg, mem_mode);
 
+  if (non_prefixed == NON_PREFIXED_X && is_lfs_stfs_insn (insn))
+    return address_is_prefixed (XEXP (mem, 0), mem_mode, NON_PREFIXED_DEFAULT);
+  else
     return address_is_prefixed (XEXP (mem, 0), mem_mode, non_prefixed);
 }
 
@@ -25168,7 +25181,7 @@ prefixed_store_p (rtx_insn *insn)
   /* Need to make sure we aren't looking at a stfs which doesn't look
      like the other things reg_to_non_prefixed/address_is_prefixed
      looks for.  */
-  if (non_prefixed == NON_PREFIXED_X && is_stfs_insn (insn))
+  if (non_prefixed == NON_PREFIXED_X && is_lfs_stfs_insn (insn))
     return address_is_prefixed (addr, mem_mode, NON_PREFIXED_DEFAULT);
   else
     return address_is_prefixed (addr, mem_mode, non_prefixed);