gas: invoke md_optimize_expr() also for unary expressions

Give backends a chance to see these, just as they can see binary ones.
Most of those which use this hook already cope with NULL being passed
for the left operand (typically because of checking the operator first).
Adjust the two which don't.

Take the opportunity and also document the hook.

4 files changed, 40 insertions, 22 deletions

diff --git a/gas/config/tc-hppa.c b/gas/config/tc-hppa.c
index c91b2b5..2e5de07 100644
--- a/gas/config/tc-hppa.c
+++ b/gas/config/tc-hppa.c
@@ -6354,6 +6354,7 @@ hppa_force_reg_syms_absolute (expressionS *resultP,
 			      expressionS *rightP)
 {
   if (fudge_reg_expressions
+      && resultP
       && rightP->X_op == O_register
       && resultP->X_op == O_register)
     {
diff --git a/gas/config/tc-ppc.c b/gas/config/tc-ppc.c
index 8b1d995..a8b034c 100644
--- a/gas/config/tc-ppc.c
+++ b/gas/config/tc-ppc.c
@@ -945,9 +945,9 @@ ppc_optimize_expr (expressionS *left, operatorT op, expressionS *right)
     }
 
   /* Accept the above plus <cr bit>, and <cr bit> plus the above.  */
-  if (right->X_op == O_register
+  if (op == O_add
       && left->X_op == O_register
-      && op == O_add
+      && right->X_op == O_register
       && ((right->X_md == PPC_OPERAND_CR_BIT
 	   && left->X_md == (PPC_OPERAND_CR_REG | PPC_OPERAND_CR_BIT))
 	  || (right->X_md == (PPC_OPERAND_CR_REG | PPC_OPERAND_CR_BIT)
@@ -959,7 +959,7 @@ ppc_optimize_expr (expressionS *left, operatorT op, expressionS *right)
     }
 
   /* Accept reg +/- constant.  */
-  if (left->X_op == O_register
+  if (left && left->X_op == O_register
       && !((op == O_add || op == O_subtract) && right->X_op == O_constant))
     as_warn (_("invalid register expression"));
 
diff --git a/gas/doc/internals.texi b/gas/doc/internals.texi
index 56f10fd..3eea25b 100644
--- a/gas/doc/internals.texi
+++ b/gas/doc/internals.texi
@@ -1047,6 +1047,14 @@ pointer, for any expression that can not be recognized.  When the function
 is called, @code{input_line_pointer} will point to the start of the
 expression.
 
+@item md_optimize_expr
+@cindex md_optimize_expr
+GAS will call this function before trying to carry out certain operations,
+like the adding of two constants.  The function is passed the left-hand
+operand, an @code{expressionS} pointer, the operator, an @code{operatorT}
+value, and the right-hand operand, again an @code{expressionS} pointer.  For
+unary expressions NULL is passed as first argument.
+
 @item md_register_arithmetic
 @cindex md_register_arithmetic
 If this macro is defined and evaluates to zero then GAS will not fold
diff --git a/gas/expr.c b/gas/expr.c
index b83296c..204cfeb 100644
--- a/gas/expr.c
+++ b/gas/expr.c
@@ -764,6 +764,7 @@ operand (expressionS *expressionP, enum expr_mode mode)
   symbolS *symbolP;	/* Points to symbol.  */
   char *name;		/* Points to name of symbol.  */
   segT segment;
+  operatorT op = O_absent; /* For unary operators.  */
 
   /* All integers are regarded as unsigned unless they are negated.
      This is because the only thing which cares whether a number is
@@ -1029,19 +1030,33 @@ operand (expressionS *expressionP, enum expr_mode mode)
       /* '~' is permitted to start a label on the Delta.  */
       if (is_name_beginner (c))
 	goto isname;
-      /* Fall through.  */
+      op = O_bit_not;
+      goto unary;
+
     case '!':
+      op = O_logical_not;
+      goto unary;
+
     case '-':
+      op = O_uminus;
+      /* Fall through.  */
     case '+':
       {
-#ifdef md_operator
       unary:
-#endif
 	operand (expressionP, mode);
+
+#ifdef md_optimize_expr
+	if (md_optimize_expr (NULL, op, expressionP))
+	{
+	  /* Skip.  */
+	  ;
+	}
+	else
+#endif
 	if (expressionP->X_op == O_constant)
 	  {
 	    /* input_line_pointer -> char after operand.  */
-	    if (c == '-')
+	    if (op == O_uminus)
 	      {
 		expressionP->X_add_number
 		  = - (addressT) expressionP->X_add_number;
@@ -1052,13 +1067,13 @@ operand (expressionS *expressionP, enum expr_mode mode)
 		if (expressionP->X_add_number)
 		  expressionP->X_extrabit ^= 1;
 	      }
-	    else if (c == '~' || c == '"')
+	    else if (op == O_bit_not)
 	      {
 		expressionP->X_add_number = ~ expressionP->X_add_number;
 		expressionP->X_extrabit ^= 1;
 		expressionP->X_unsigned = 0;
 	      }
-	    else if (c == '!')
+	    else if (op == O_logical_not)
 	      {
 		expressionP->X_add_number = ! expressionP->X_add_number;
 		expressionP->X_unsigned = 1;
@@ -1067,7 +1082,7 @@ operand (expressionS *expressionP, enum expr_mode mode)
 	  }
 	else if (expressionP->X_op == O_big
 		 && expressionP->X_add_number <= 0
-		 && c == '-'
+		 && op == O_uminus
 		 && (generic_floating_point_number.sign == '+'
 		     || generic_floating_point_number.sign == 'P'))
 	  {
@@ -1082,7 +1097,7 @@ operand (expressionS *expressionP, enum expr_mode mode)
 	  {
 	    int i;
 
-	    if (c == '~' || c == '-')
+	    if (op == O_uminus || op == O_bit_not)
 	      {
 		for (i = 0; i < expressionP->X_add_number; ++i)
 		  generic_bignum[i] = ~generic_bignum[i];
@@ -1095,7 +1110,7 @@ operand (expressionS *expressionP, enum expr_mode mode)
 		      generic_bignum[i] = ~(LITTLENUM_TYPE) 0;
 		  }
 
-		if (c == '-')
+		if (op == O_uminus)
 		  for (i = 0; i < expressionP->X_add_number; ++i)
 		    {
 		      generic_bignum[i] += 1;
@@ -1103,7 +1118,7 @@ operand (expressionS *expressionP, enum expr_mode mode)
 			break;
 		    }
 	      }
-	    else if (c == '!')
+	    else if (op == O_logical_not)
 	      {
 		for (i = 0; i < expressionP->X_add_number; ++i)
 		  if (generic_bignum[i] != 0)
@@ -1117,15 +1132,10 @@ operand (expressionS *expressionP, enum expr_mode mode)
 	else if (expressionP->X_op != O_illegal
 		 && expressionP->X_op != O_absent)
 	  {
-	    if (c != '+')
+	    if (op != O_absent)
 	      {
 		expressionP->X_add_symbol = make_expr_symbol (expressionP);
-		if (c == '-')
-		  expressionP->X_op = O_uminus;
-		else if (c == '~' || c == '"')
-		  expressionP->X_op = O_bit_not;
-		else
-		  expressionP->X_op = O_logical_not;
+		expressionP->X_op = op;
 		expressionP->X_add_number = 0;
 	      }
 	    else if (!md_register_arithmetic && expressionP->X_op == O_register)
@@ -1288,8 +1298,7 @@ operand (expressionS *expressionP, enum expr_mode mode)
 
 #ifdef md_operator
 	  {
-	    operatorT op = md_operator (name, 1, &c);
-
+	    op = md_operator (name, 1, &c);
 	    switch (op)
 	      {
 	      case O_uminus: