constraint: fix relaxed memory and repeated constraint handling

The function `constrain_operands' lacked the logic to consider relaxed
memory constraints when "traditional" memory constraints were not
satisfied, creating potential issues as observed during the reload
compilation pass.

In addition, it was observed that while `constrain_operands' chooses
to disregard constraints when more than one alternative is provided,
e.g. "m,r" using CONSTRAINT__UNKNOWN, it has no checks in place to
determine whether the multiple constraints in a given string are in
fact repetitions of the same constraint and should thus in fact be
treated as a single constraint, as ought to be the case for something
like "m,m".

Both of these issues are dealt with here, thus ensuring that we get
appropriate pattern matching.

gcc/
	* lra-constraints.cc (constraint_unique): New.
	(process_address_1): Apply constraint_unique test.
	* recog.cc (constrain_operands): Allow relaxed memory
	constaints.

2 files changed, 38 insertions, 4 deletions

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index ff4e8f0..b231cb6 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -3450,6 +3450,41 @@ skip_constraint_modifiers (const char *str)
       }
 }
 
+/* Takes a string of 0 or more comma-separated constraints.  When more
+   than one constraint is present, evaluate whether they all correspond
+   to a single, repeated constraint (e.g. "r,r") or whether we have
+   more than one distinct constraints (e.g. "r,m").  */
+static bool
+constraint_unique (const char *cstr)
+{
+  enum constraint_num ca, cb;
+  ca = CONSTRAINT__UNKNOWN;
+  for (;;)
+    {
+      cstr = skip_constraint_modifiers (cstr);
+      if (*cstr == '\0' || *cstr == ',')
+	cb = CONSTRAINT_X;
+      else
+	{
+	  cb = lookup_constraint (cstr);
+	  if (cb == CONSTRAINT__UNKNOWN)
+	    return false;
+	  cstr += CONSTRAINT_LEN (cstr[0], cstr);
+	}
+      /* Handle the first iteration of the loop.  */
+      if (ca == CONSTRAINT__UNKNOWN)
+	ca = cb;
+      /* Handle the general case of comparing ca with subsequent
+	 constraints.  */
+      else if (ca != cb)
+	return false;
+      if (*cstr == '\0')
+	return true;
+      if (*cstr == ',')
+	cstr += 1;
+    }
+}
+
 /* Major function to make reloads for an address in operand NOP or
    check its correctness (If CHECK_ONLY_P is true). The supported
    cases are:
@@ -3509,9 +3544,7 @@ process_address_1 (int nop, bool check_only_p,
      operand has one address constraint, probably all others constraints are
      address ones.  */
   if (constraint[0] != '\0' && get_constraint_type (cn) != CT_ADDRESS
-      && *skip_constraint_modifiers (constraint
-				     + CONSTRAINT_LEN (constraint[0],
-						       constraint)) != '\0')
+      && !constraint_unique (constraint))
     cn = CONSTRAINT__UNKNOWN;
   if (insn_extra_address_constraint (cn)
       /* When we find an asm operand with an address constraint that
diff --git a/gcc/recog.cc b/gcc/recog.cc
index 200cf42..3ddeab5 100644
--- a/gcc/recog.cc
+++ b/gcc/recog.cc
@@ -3234,7 +3234,8 @@ constrain_operands (int strict, alternative_mask alternatives)
 		  else if (constraint_satisfied_p (op, cn))
 		    win = 1;
 
-		  else if (insn_extra_memory_constraint (cn)
+		  else if ((insn_extra_memory_constraint (cn)
+			    || insn_extra_relaxed_memory_constraint (cn))
 			   /* Every memory operand can be reloaded to fit.  */
 			   && ((strict < 0 && MEM_P (op))
 			       /* Before reload, accept what reload can turn