Initial revision

gas/expr.c

@@ -0,0 +1,966 @@
+/* expr.c -operands, expressions-
+   Copyright (C) 1987, 1990, 1991 Free Software Foundation, Inc.
+
+This file is part of GAS, the GNU Assembler.
+
+GAS is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 1, or (at your option)
+any later version.
+
+GAS is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GAS; see the file COPYING.  If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+/* static const char rcsid[] = "$Id$"; */
+
+/*
+ * This is really a branch office of as-read.c. I split it out to clearly
+ * distinguish the world of expressions from the world of statements.
+ * (It also gives smaller files to re-compile.)
+ * Here, "operand"s are of expressions, not instructions.
+ */
+
+#include <ctype.h>
+#include <string.h>
+
+#include "as.h"
+
+#include "obstack.h"
+
+#ifdef __STDC__
+static void clean_up_expression(expressionS *expressionP);
+#else /* __STDC__ */
+static void clean_up_expression();	/* Internal. */
+#endif /* __STDC__ */
+extern const char EXP_CHARS[];	/* JF hide MD floating pt stuff all the same place */
+extern const char FLT_CHARS[];
+
+#ifdef LOCAL_LABELS_DOLLAR
+extern int local_label_defined[];
+#endif
+
+/*
+ * Build any floating-point literal here.
+ * Also build any bignum literal here.
+ */
+
+/* LITTLENUM_TYPE	generic_buffer [6]; */	/* JF this is a hack */
+/* Seems atof_machine can backscan through generic_bignum and hit whatever
+   happens to be loaded before it in memory.  And its way too complicated
+   for me to fix right.  Thus a hack.  JF:  Just make generic_bignum bigger,
+   and never write into the early words, thus they'll always be zero.
+   I hate Dean's floating-point code.  Bleh.
+ */
+LITTLENUM_TYPE	generic_bignum [SIZE_OF_LARGE_NUMBER+6];
+FLONUM_TYPE	generic_floating_point_number =
+{
+  & generic_bignum [6],		/* low (JF: Was 0) */
+  & generic_bignum [SIZE_OF_LARGE_NUMBER+6 - 1], /* high JF: (added +6) */
+  0,				/* leader */
+  0,				/* exponent */
+  0				/* sign */
+};
+/* If nonzero, we've been asked to assemble nan, +inf or -inf */
+int generic_floating_point_magic;
+
+/*
+ * Summary of operand().
+ *
+ * in:	Input_line_pointer points to 1st char of operand, which may
+ *	be a space.
+ *
+ * out:	A expressionS. X_seg determines how to understand the rest of the
+ *	expressionS.
+ *	The operand may have been empty: in this case X_seg == SEG_ABSENT.
+ *	Input_line_pointer->(next non-blank) char after operand.
+ *
+ */
+
+static segT
+operand (expressionP)
+     register expressionS *	expressionP;
+{
+  register char c;
+  register char *name;	/* points to name of symbol */
+  register symbolS *	symbolP; /* Points to symbol */
+
+  extern  char hex_value[];	/* In hex_value.c */
+
+  SKIP_WHITESPACE();		/* Leading whitespace is part of operand. */
+  c = * input_line_pointer ++;	/* Input_line_pointer->past char in c. */
+  if (isdigit(c))
+    {
+      register valueT	number;	/* offset or (absolute) value */
+      register short int digit;	/* value of next digit in current radix */
+				/* invented for humans only, hope */
+				/* optimising compiler flushes it! */
+      register short int radix;	/* 2, 8, 10 or 16 */
+				/* 0 means we saw start of a floating- */
+				/* point constant. */
+      register short int maxdig = 0;/* Highest permitted digit value. */
+      register int too_many_digits = 0; /* If we see >= this number of */
+				/* digits, assume it is a bignum. */
+      register char *	digit_2; /*->2nd digit of number. */
+               int small;	/* TRUE if fits in 32 bits. */
+
+      if (c == '0') {			/* non-decimal radix */
+	      if ((c = *input_line_pointer ++)=='x' || c=='X') {
+		      c = *input_line_pointer ++; /* read past "0x" or "0X" */
+		      maxdig = radix = 16;
+		      too_many_digits = 9;
+	      } else {
+		      /* If it says '0f' and the line ends or it DOESN'T look like
+			 a floating point #, its a local label ref.  DTRT */
+		      /* likewise for the b's.  xoxorich. */
+		      if ((c == 'f' || c == 'b' || c == 'B')
+			  && (!*input_line_pointer ||
+			      (!strchr("+-.0123456789",*input_line_pointer) &&
+			       !strchr(EXP_CHARS,*input_line_pointer)))) {
+			      maxdig = radix = 10;
+			      too_many_digits = 11;
+			      c = '0';
+			      input_line_pointer -= 2;
+
+		      } else if (c == 'b' || c == 'B') {
+			      c = *input_line_pointer++;
+			      maxdig = radix = 2;
+			      too_many_digits = 33;
+
+		      } else if (c && strchr(FLT_CHARS,c)) {
+			      radix = 0;	/* Start of floating-point constant. */
+			      /* input_line_pointer->1st char of number. */
+			      expressionP->X_add_number =  -(isupper(c) ? tolower(c) : c);
+
+		      } else {		/* By elimination, assume octal radix. */
+			      radix = maxdig = 8;
+			      too_many_digits = 11;
+		      }
+	      } /* c == char after "0" or "0x" or "0X" or "0e" etc. */
+      } else {
+	      maxdig = radix = 10;
+	      too_many_digits = 11;
+      } /* if operand starts with a zero */
+
+      if (radix) {			/* Fixed-point integer constant. */
+				/* May be bignum, or may fit in 32 bits. */
+/*
+ * Most numbers fit into 32 bits, and we want this case to be fast.
+ * So we pretend it will fit into 32 bits. If, after making up a 32
+ * bit number, we realise that we have scanned more digits than
+ * comfortably fit into 32 bits, we re-scan the digits coding
+ * them into a bignum. For decimal and octal numbers we are conservative: some
+ * numbers may be assumed bignums when in fact they do fit into 32 bits.
+ * Numbers of any radix can have excess leading zeros: we strive
+ * to recognise this and cast them back into 32 bits.
+ * We must check that the bignum really is more than 32
+ * bits, and change it back to a 32-bit number if it fits.
+ * The number we are looking for is expected to be positive, but
+ * if it fits into 32 bits as an unsigned number, we let it be a 32-bit
+ * number. The cavalier approach is for speed in ordinary cases.
+ */
+	  digit_2 = input_line_pointer;
+	  for (number=0;  (digit=hex_value[c])<maxdig;  c = * input_line_pointer ++)
+	    {
+	      number = number * radix + digit;
+	    }
+	  /* C contains character after number. */
+	  /* Input_line_pointer->char after C. */
+	  small = input_line_pointer - digit_2 < too_many_digits;
+	  if (! small)
+	    {
+	      /*
+	       * We saw a lot of digits. Manufacture a bignum the hard way.
+ */
+	      LITTLENUM_TYPE *	leader;	/*->high order littlenum of the bignum. */
+	      LITTLENUM_TYPE *	pointer; /*->littlenum we are frobbing now. */
+	      long carry;
+
+	      leader = generic_bignum;
+	      generic_bignum [0] = 0;
+	      generic_bignum [1] = 0;
+				/* We could just use digit_2, but lets be mnemonic. */
+	      input_line_pointer = -- digit_2; /*->1st digit. */
+	      c = *input_line_pointer ++;
+	      for (;   (carry = hex_value [c]) < maxdig;   c = * input_line_pointer ++)
+		{
+		  for (pointer = generic_bignum;
+		       pointer <= leader;
+		       pointer ++)
+		    {
+		      long work;
+
+		      work = carry + radix * * pointer;
+		      * pointer = work & LITTLENUM_MASK;
+		      carry = work >> LITTLENUM_NUMBER_OF_BITS;
+		    }
+		  if (carry)
+		    {
+		      if (leader < generic_bignum + SIZE_OF_LARGE_NUMBER - 1)
+			{	/* Room to grow a longer bignum. */
+			  * ++ leader = carry;
+			}
+		    }
+		}
+	      /* Again, C is char after number, */
+	      /* input_line_pointer->after C. */
+	      know(sizeof (int) * 8 == 32);
+	      know(LITTLENUM_NUMBER_OF_BITS == 16);
+	      /* Hence the constant "2" in the next line. */
+	      if (leader < generic_bignum + 2)
+		{		/* Will fit into 32 bits. */
+		  number =
+		    ((generic_bignum [1] & LITTLENUM_MASK) << LITTLENUM_NUMBER_OF_BITS)
+		    | (generic_bignum [0] & LITTLENUM_MASK);
+		  small = 1;
+		}
+	      else
+		{
+		  number = leader - generic_bignum + 1;	/* Number of littlenums in the bignum. */
+		}
+	    }
+	  if (small)
+	    {
+	      /*
+	       * Here with number, in correct radix. c is the next char.
+	       * Note that unlike Un*x, we allow "011f" "0x9f" to
+	       * both mean the same as the (conventional) "9f". This is simply easier
+	       * than checking for strict canonical form. Syntax sux!
+ */
+	      if (number<10)
+		{
+		  if (0
+#ifdef LOCAL_LABELS_FB
+		       || c=='b'
+#endif
+#ifdef LOCAL_LABELS_DOLLAR
+		       || (c=='$' && local_label_defined[number])
+#endif
+		      )
+		    {
+		      /*
+		       * Backward ref to local label.
+		       * Because it is backward, expect it to be DEFINED.
+		       */
+		      /*
+		       * Construct a local label.
+		       */
+		      name = local_label_name ((int)number, 0);
+		      if (((symbolP = symbol_find(name)) != NULL) /* seen before */
+			  && (S_IS_DEFINED(symbolP))) /* symbol is defined: OK */
+			{		/* Expected path: symbol defined. */
+			  /* Local labels are never absolute. Don't waste time checking absoluteness. */
+			  know((S_GET_SEGMENT(symbolP) == SEG_DATA) || (S_GET_SEGMENT(symbolP) == SEG_TEXT));
+			  expressionP->X_add_symbol = symbolP;
+			  expressionP->X_add_number = 0;
+			  expressionP->X_seg = S_GET_SEGMENT(symbolP);
+			}
+		      else
+			{		/* Either not seen or not defined. */
+			  as_bad("Backw. ref to unknown label \"%d:\", 0 assumed.",
+				  number);
+			  expressionP->X_add_number = 0;
+			  expressionP->X_seg        = SEG_ABSOLUTE;
+			}
+		    }
+		  else
+		    {
+		      if (0
+#ifdef LOCAL_LABELS_FB
+			  || c == 'f'
+#endif
+#ifdef LOCAL_LABELS_DOLLAR
+		          || (c=='$' && !local_label_defined[number])
+#endif
+			  )
+			{
+			  /*
+			   * Forward reference. Expect symbol to be undefined or
+			   * unknown. Undefined: seen it before. Unknown: never seen
+			   * it in this pass.
+			   * Construct a local label name, then an undefined symbol.
+			   * Don't create a XSEG frag for it: caller may do that.
+			   * Just return it as never seen before.
+			   */
+			  name = local_label_name((int)number, 1);
+			  symbolP = symbol_find_or_make(name);
+			  /* We have no need to check symbol properties. */
+			  know(S_GET_SEGMENT(symbolP) == SEG_UNKNOWN
+			       || S_GET_SEGMENT(symbolP) == SEG_TEXT
+			       || S_GET_SEGMENT(symbolP) == SEG_DATA);
+			  expressionP->X_add_symbol      = symbolP;
+			  expressionP->X_seg             = SEG_UNKNOWN;
+			  expressionP->X_subtract_symbol = NULL;
+			  expressionP->X_add_number      = 0;
+			}
+		      else
+			{		/* Really a number, not a local label. */
+			  expressionP->X_add_number = number;
+			  expressionP->X_seg        = SEG_ABSOLUTE;
+			  input_line_pointer --; /* Restore following character. */
+			}		/* if (c=='f') */
+		    }			/* if (c=='b') */
+		}
+	      else
+		{			/* Really a number. */
+		  expressionP->X_add_number = number;
+		  expressionP->X_seg        = SEG_ABSOLUTE;
+		  input_line_pointer --; /* Restore following character. */
+		}			/* if (number<10) */
+	    }
+	  else
+	    {
+	      expressionP->X_add_number = number;
+	      expressionP->X_seg = SEG_BIG;
+	      input_line_pointer --; /*->char following number. */
+	    }			/* if (small) */
+	}			/* (If integer constant) */
+      else
+	{			/* input_line_pointer->*/
+				/* floating-point constant. */
+	  int error_code;
+
+	  error_code = atof_generic
+	    (& input_line_pointer, ".", EXP_CHARS,
+	     & generic_floating_point_number);
+
+	  if (error_code)
+	    {
+	      if (error_code == ERROR_EXPONENT_OVERFLOW)
+		{
+		  as_bad("Bad floating-point constant: exponent overflow, probably assembling junk");
+		}
+	      else
+		{
+		  as_bad("Bad floating-point constant: unknown error code=%d.", error_code);
+		}
+	    }
+	  expressionP->X_seg = SEG_BIG;
+				/* input_line_pointer->just after constant, */
+				/* which may point to whitespace. */
+	  know(expressionP->X_add_number < 0); /* < 0 means "floating point". */
+	}			/* if (not floating-point constant) */
+    }
+  else if(c=='.' && !is_part_of_name(*input_line_pointer)) {
+    extern struct obstack frags;
+
+    /*
+       JF:  '.' is pseudo symbol with value of current location in current
+       segment. . .
+ */
+    symbolP = symbol_new("L0\001",
+			 now_seg,
+			 (valueT)(obstack_next_free(&frags)-frag_now->fr_literal),
+			 frag_now);
+
+    expressionP->X_add_number=0;
+    expressionP->X_add_symbol=symbolP;
+    expressionP->X_seg = now_seg;
+
+  } else if (is_name_beginner(c)) /* here if did not begin with a digit */
+    {
+      /*
+       * Identifier begins here.
+       * This is kludged for speed, so code is repeated.
+       */
+      name =  -- input_line_pointer;
+      c = get_symbol_end();
+      symbolP = symbol_find_or_make(name);
+      /*
+       * If we have an absolute symbol or a reg, then we know its value now.
+       */
+      expressionP->X_seg = S_GET_SEGMENT(symbolP);
+      switch (expressionP->X_seg)
+	{
+	case SEG_ABSOLUTE:
+	case SEG_REGISTER:
+	  expressionP->X_add_number = S_GET_VALUE(symbolP);
+	  break;
+
+        default:
+	  expressionP->X_add_number  = 0;
+	  expressionP->X_add_symbol  = symbolP;
+	}
+      * input_line_pointer = c;
+      expressionP->X_subtract_symbol = NULL;
+    }
+  else if (c=='(')/* didn't begin with digit & not a name */
+    {
+      (void)expression(expressionP);
+      /* Expression() will pass trailing whitespace */
+      if (* input_line_pointer ++ != ')')
+	{
+	  as_bad("Missing ')' assumed");
+	  input_line_pointer --;
+	}
+      /* here with input_line_pointer->char after "(...)" */
+    }
+  else if (c == '~' || c == '-' || c == '+') {
+	  /* unary operator: hope for SEG_ABSOLUTE */
+      switch (operand (expressionP)) {
+      case SEG_ABSOLUTE:
+	      /* input_line_pointer->char after operand */
+	      if (c=='-') {
+		      expressionP->X_add_number = - expressionP->X_add_number;
+		      /*
+		       * Notice: '-' may  overflow: no warning is given. This is compatible
+		       * with other people's assemblers. Sigh.
+		       */
+	      } else if (c == '~') {
+		      expressionP->X_add_number = ~ expressionP->X_add_number;
+	      } else if (c != '+') {
+		      know(0);
+	      } /* switch on unary operator */
+	      break;
+
+      case SEG_TEXT:
+      case SEG_DATA:
+      case SEG_BSS:
+      case SEG_PASS1:
+      case SEG_UNKNOWN:
+	if(c=='-') {		/* JF I hope this hack works */
+	  expressionP->X_subtract_symbol=expressionP->X_add_symbol;
+	  expressionP->X_add_symbol=0;
+	  expressionP->X_seg=SEG_DIFFERENCE;
+	  break;
+	}
+      default:		/* unary on non-absolute is unsuported */
+	as_bad("Unary operator %c ignored because bad operand follows", c);
+	break;
+	/* Expression undisturbed from operand(). */
+      }
+    }
+  else if (c=='\'')
+    {
+/*
+ * Warning: to conform to other people's assemblers NO ESCAPEMENT is permitted
+ * for a single quote. The next character, parity errors and all, is taken
+ * as the value of the operand. VERY KINKY.
+ */
+      expressionP->X_add_number = * input_line_pointer ++;
+      expressionP->X_seg        = SEG_ABSOLUTE;
+    }
+  else
+    {
+		      /* can't imagine any other kind of operand */
+      expressionP->X_seg = SEG_ABSENT;
+      input_line_pointer --;
+      md_operand (expressionP);
+    }
+/*
+ * It is more 'efficient' to clean up the expressions when they are created.
+ * Doing it here saves lines of code.
+ */
+  clean_up_expression (expressionP);
+  SKIP_WHITESPACE();		/*->1st char after operand. */
+  know(* input_line_pointer != ' ');
+  return (expressionP->X_seg);
+} /* operand() */
+
+/* Internal. Simplify a struct expression for use by expr() */
+
+/*
+ * In:	address of a expressionS.
+ *	The X_seg field of the expressionS may only take certain values.
+ *	Now, we permit SEG_PASS1 to make code smaller & faster.
+ *	Elsewise we waste time special-case testing. Sigh. Ditto SEG_ABSENT.
+ * Out:	expressionS may have been modified:
+ *	'foo-foo' symbol references cancelled to 0,
+ *		which changes X_seg from SEG_DIFFERENCE to SEG_ABSOLUTE;
+ *	Unused fields zeroed to help expr().
+ */
+
+static void
+clean_up_expression (expressionP)
+     register expressionS * expressionP;
+{
+  switch (expressionP->X_seg)
+    {
+    case SEG_ABSENT:
+    case SEG_PASS1:
+      expressionP->X_add_symbol	= NULL;
+      expressionP->X_subtract_symbol	= NULL;
+      expressionP->X_add_number	= 0;
+      break;
+
+    case SEG_BIG:
+    case SEG_ABSOLUTE:
+      expressionP->X_subtract_symbol	= NULL;
+      expressionP->X_add_symbol	= NULL;
+      break;
+
+    case SEG_TEXT:
+    case SEG_DATA:
+    case SEG_BSS:
+    case SEG_UNKNOWN:
+      expressionP->X_subtract_symbol	= NULL;
+      break;
+
+    case SEG_DIFFERENCE:
+      /*
+       * It does not hurt to 'cancel' NULL==NULL
+       * when comparing symbols for 'eq'ness.
+       * It is faster to re-cancel them to NULL
+       * than to check for this special case.
+ */
+      if (expressionP->X_subtract_symbol == expressionP->X_add_symbol
+          || (expressionP->X_subtract_symbol
+	      && expressionP->X_add_symbol
+  	      && expressionP->X_subtract_symbol->sy_frag==expressionP->X_add_symbol->sy_frag
+	      && S_GET_VALUE(expressionP->X_subtract_symbol) == S_GET_VALUE(expressionP->X_add_symbol))) {
+	      expressionP->X_subtract_symbol	= NULL;
+	      expressionP->X_add_symbol		= NULL;
+	      expressionP->X_seg			= SEG_ABSOLUTE;
+      }
+      break;
+
+    case SEG_REGISTER:
+      expressionP->X_add_symbol	= NULL;
+      expressionP->X_subtract_symbol	= NULL;
+      break;
+
+    default:
+      BAD_CASE (expressionP->X_seg);
+      break;
+    }
+} /* clean_up_expression() */
+
+/*
+ *			expr_part ()
+ *
+ * Internal. Made a function because this code is used in 2 places.
+ * Generate error or correct X_?????_symbol of expressionS.
+ */
+
+/*
+ * symbol_1 += symbol_2 ... well ... sort of.
+ */
+
+static segT
+expr_part (symbol_1_PP, symbol_2_P)
+     symbolS **	symbol_1_PP;
+     symbolS *	symbol_2_P;
+{
+  segT			return_value;
+
+  know((* symbol_1_PP)           		== NULL
+       || (S_GET_SEGMENT(*symbol_1_PP) == SEG_TEXT)
+       || (S_GET_SEGMENT(*symbol_1_PP) == SEG_DATA)
+       || (S_GET_SEGMENT(*symbol_1_PP) == SEG_BSS)
+       || (!S_IS_DEFINED(* symbol_1_PP)));
+  know(symbol_2_P             == NULL
+       || (S_GET_SEGMENT(symbol_2_P) == SEG_TEXT)
+       || (S_GET_SEGMENT(symbol_2_P) == SEG_DATA)
+       || (S_GET_SEGMENT(symbol_2_P) == SEG_BSS)
+       || (!S_IS_DEFINED(symbol_2_P)));
+  if (* symbol_1_PP)
+    {
+      if (!S_IS_DEFINED(* symbol_1_PP))
+	{
+	  if (symbol_2_P)
+	    {
+	      return_value = SEG_PASS1;
+	      * symbol_1_PP = NULL;
+	    }
+	  else
+	    {
+	      know(!S_IS_DEFINED(* symbol_1_PP));
+	      return_value = SEG_UNKNOWN;
+	    }
+	}
+      else
+	{
+	  if (symbol_2_P)
+	    {
+	      if (!S_IS_DEFINED(symbol_2_P))
+		{
+		  * symbol_1_PP = NULL;
+		  return_value = SEG_PASS1;
+		}
+	      else
+		{
+		  /* {seg1} - {seg2} */
+		  as_bad("Expression too complex, 2 symbols forgotten: \"%s\" \"%s\"",
+			  S_GET_NAME(* symbol_1_PP), S_GET_NAME(symbol_2_P));
+		  * symbol_1_PP = NULL;
+		  return_value = SEG_ABSOLUTE;
+		}
+	    }
+	  else
+	    {
+	      return_value = S_GET_SEGMENT(* symbol_1_PP);
+	    }
+	}
+    }
+  else
+    {				/* (* symbol_1_PP) == NULL */
+      if (symbol_2_P)
+	{
+	  * symbol_1_PP = symbol_2_P;
+	  return_value = S_GET_SEGMENT(symbol_2_P);
+	}
+      else
+	{
+	  * symbol_1_PP = NULL;
+	  return_value = SEG_ABSOLUTE;
+	}
+    }
+  know(return_value == SEG_ABSOLUTE
+       || return_value == SEG_TEXT
+       || return_value == SEG_DATA
+       || return_value == SEG_BSS
+       || return_value == SEG_UNKNOWN
+       || return_value == SEG_PASS1);
+  know((* symbol_1_PP) == NULL
+       || (S_GET_SEGMENT(* symbol_1_PP) == return_value));
+  return (return_value);
+}				/* expr_part() */
+
+/* Expression parser. */
+
+/*
+ * We allow an empty expression, and just assume (absolute,0) silently.
+ * Unary operators and parenthetical expressions are treated as operands.
+ * As usual, Q==quantity==operand, O==operator, X==expression mnemonics.
+ *
+ * We used to do a aho/ullman shift-reduce parser, but the logic got so
+ * warped that I flushed it and wrote a recursive-descent parser instead.
+ * Now things are stable, would anybody like to write a fast parser?
+ * Most expressions are either register (which does not even reach here)
+ * or 1 symbol. Then "symbol+constant" and "symbol-symbol" are common.
+ * So I guess it doesn't really matter how inefficient more complex expressions
+ * are parsed.
+ *
+ * After expr(RANK,resultP) input_line_pointer->operator of rank <= RANK.
+ * Also, we have consumed any leading or trailing spaces (operand does that)
+ * and done all intervening operators.
+ */
+
+typedef enum
+{
+O_illegal,			/* (0)  what we get for illegal op */
+
+O_multiply,			/* (1)  * */
+O_divide,			/* (2)  / */
+O_modulus,			/* (3)  % */
+O_left_shift,			/* (4)  < */
+O_right_shift,			/* (5)  > */
+O_bit_inclusive_or,		/* (6)  | */
+O_bit_or_not,			/* (7)  ! */
+O_bit_exclusive_or,		/* (8)  ^ */
+O_bit_and,			/* (9)  & */
+O_add,				/* (10) + */
+O_subtract			/* (11) - */
+}
+operatorT;
+
+#define __ O_illegal
+
+static const operatorT op_encoding [256] = {	/* maps ASCII->operators */
+
+__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
+
+__, O_bit_or_not, __, __, __, O_modulus, O_bit_and, __,
+__, __, O_multiply, O_add, __, O_subtract, __, O_divide,
+__, __, __, __, __, __, __, __,
+__, __, __, __, O_left_shift, __, O_right_shift, __,
+__, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __,
+__, __, __, __, __, __, O_bit_exclusive_or, __,
+__, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __,
+__, __, __, __, O_bit_inclusive_or, __, __, __,
+
+__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
+__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __
+};
+
+
+/*
+ *	Rank	Examples
+ *	0	operand, (expression)
+ *	1	+ -
+ *	2	& ^ ! |
+ *	3	* / % << >>
+ */
+static const operator_rankT
+op_rank [] = { 0, 3, 3, 3, 3, 3, 2, 2, 2, 2, 1, 1 };
+
+/* Return resultP->X_seg. */
+segT expr(rank, resultP)
+register operator_rankT	rank; /* Larger # is higher rank. */
+register expressionS *resultP; /* Deliver result here. */
+{
+  expressionS		right;
+  register operatorT	op_left;
+  register char c_left;	/* 1st operator character. */
+  register operatorT	op_right;
+  register char c_right;
+
+  know(rank >= 0);
+  (void)operand (resultP);
+  know(* input_line_pointer != ' '); /* Operand() gobbles spaces. */
+  c_left = * input_line_pointer; /* Potential operator character. */
+  op_left = op_encoding [c_left];
+  while (op_left != O_illegal && op_rank [(int) op_left] > rank)
+    {
+      input_line_pointer ++;	/*->after 1st character of operator. */
+				/* Operators "<<" and ">>" have 2 characters. */
+      if (* input_line_pointer == c_left && (c_left == '<' || c_left == '>'))
+	{
+	  input_line_pointer ++;
+	}			/*->after operator. */
+      if (SEG_ABSENT == expr (op_rank[(int) op_left], &right))
+	{
+	  as_warn("Missing operand value assumed absolute 0.");
+	  resultP->X_add_number	= 0;
+	  resultP->X_subtract_symbol	= NULL;
+	  resultP->X_add_symbol	= NULL;
+	  resultP->X_seg = SEG_ABSOLUTE;
+	}
+      know(* input_line_pointer != ' ');
+      c_right = * input_line_pointer;
+      op_right = op_encoding [c_right];
+      if (* input_line_pointer == c_right && (c_right == '<' || c_right == '>'))
+	{
+	  input_line_pointer ++;
+	}			/*->after operator. */
+      know((int) op_right == 0
+	   || op_rank [(int) op_right] <= op_rank[(int) op_left]);
+      /* input_line_pointer->after right-hand quantity. */
+      /* left-hand quantity in resultP */
+      /* right-hand quantity in right. */
+      /* operator in op_left. */
+      if (resultP->X_seg == SEG_PASS1 || right . X_seg == SEG_PASS1)
+	{
+	  resultP->X_seg = SEG_PASS1;
+	}
+      else
+	{
+	  if (resultP->X_seg == SEG_BIG)
+	    {
+	      as_warn("Left operand of %c is a %s.  Integer 0 assumed.",
+		      c_left, resultP->X_add_number > 0 ? "bignum" : "float");
+	      resultP->X_seg = SEG_ABSOLUTE;
+	      resultP->X_add_symbol = 0;
+	      resultP->X_subtract_symbol = 0;
+	      resultP->X_add_number = 0;
+	    }
+	  if (right . X_seg == SEG_BIG)
+	    {
+	      as_warn("Right operand of %c is a %s.  Integer 0 assumed.",
+		      c_left, right . X_add_number > 0 ? "bignum" : "float");
+	      right . X_seg = SEG_ABSOLUTE;
+	      right . X_add_symbol = 0;
+	      right . X_subtract_symbol = 0;
+	      right . X_add_number = 0;
+	    }
+	  if (op_left == O_subtract)
+	    {
+	      /*
+	       * Convert - into + by exchanging symbols and negating number.
+	       * I know -infinity can't be negated in 2's complement:
+	       * but then it can't be subtracted either. This trick
+	       * does not cause any further inaccuracy.
+	       */
+
+	      register symbolS *	symbolP;
+
+	      right . X_add_number      = - right . X_add_number;
+	      symbolP                   = right . X_add_symbol;
+	      right . X_add_symbol	= right . X_subtract_symbol;
+	      right . X_subtract_symbol = symbolP;
+	      if (symbolP)
+		{
+		  right . X_seg		= SEG_DIFFERENCE;
+		}
+	      op_left = O_add;
+	    }
+
+	  if (op_left == O_add)
+	    {
+	      segT	seg1;
+	      segT	seg2;
+
+	      know(resultP->X_seg == SEG_DATA
+		   || resultP->X_seg == SEG_TEXT
+		   || resultP->X_seg == SEG_BSS
+		   || resultP->X_seg == SEG_UNKNOWN
+		   || resultP->X_seg == SEG_DIFFERENCE
+		   || resultP->X_seg == SEG_ABSOLUTE
+		   || resultP->X_seg == SEG_PASS1);
+	      know(right .  X_seg == SEG_DATA
+		   ||   right .  X_seg == SEG_TEXT
+		   ||   right .  X_seg == SEG_BSS
+		   ||   right .  X_seg == SEG_UNKNOWN
+		   ||   right .  X_seg == SEG_DIFFERENCE
+		   ||   right .  X_seg == SEG_ABSOLUTE
+		   ||   right .  X_seg == SEG_PASS1);
+
+	      clean_up_expression (& right);
+	      clean_up_expression (resultP);
+
+	      seg1 = expr_part (& resultP->X_add_symbol, right . X_add_symbol);
+	      seg2 = expr_part (& resultP->X_subtract_symbol, right . X_subtract_symbol);
+	      if (seg1 == SEG_PASS1 || seg2 == SEG_PASS1) {
+		      need_pass_2 = 1;
+		      resultP->X_seg = SEG_PASS1;
+	      } else if (seg2 == SEG_ABSOLUTE)
+		  resultP->X_seg = seg1;
+	      else if (seg1 != SEG_UNKNOWN
+		       && seg1 != SEG_ABSOLUTE
+		       && seg2 != SEG_UNKNOWN
+		       && seg1 != seg2) {
+		      know(seg2 != SEG_ABSOLUTE);
+		      know(resultP->X_subtract_symbol);
+
+		      know(seg1 == SEG_TEXT || seg1 == SEG_DATA || seg1== SEG_BSS);
+		      know(seg2 == SEG_TEXT || seg2 == SEG_DATA || seg2== SEG_BSS);
+		      know(resultP->X_add_symbol);
+		      know(resultP->X_subtract_symbol);
+		      as_bad("Expression too complex: forgetting %s - %s",
+			      S_GET_NAME(resultP->X_add_symbol),
+			      S_GET_NAME(resultP->X_subtract_symbol));
+		      resultP->X_seg = SEG_ABSOLUTE;
+		      /* Clean_up_expression() will do the rest. */
+	      } else
+		  resultP->X_seg = SEG_DIFFERENCE;
+
+	      resultP->X_add_number += right . X_add_number;
+	      clean_up_expression (resultP);
+      }
+	  else
+	    {			/* Not +. */
+	      if (resultP->X_seg == SEG_UNKNOWN || right . X_seg == SEG_UNKNOWN)
+		{
+		  resultP->X_seg = SEG_PASS1;
+		  need_pass_2 = 1;
+		}
+	      else
+		{
+		  resultP->X_subtract_symbol = NULL;
+		  resultP->X_add_symbol = NULL;
+		  /* Will be SEG_ABSOLUTE. */
+		  if (resultP->X_seg != SEG_ABSOLUTE || right . X_seg != SEG_ABSOLUTE)
+		    {
+		      as_bad("Relocation error. Absolute 0 assumed.");
+		      resultP->X_seg        = SEG_ABSOLUTE;
+		      resultP->X_add_number = 0;
+		    }
+		  else
+		    {
+		      switch (op_left)
+			{
+			case O_bit_inclusive_or:
+			  resultP->X_add_number |= right . X_add_number;
+			  break;
+
+			case O_modulus:
+			  if (right . X_add_number)
+			    {
+			      resultP->X_add_number %= right . X_add_number;
+			    }
+			  else
+			    {
+			      as_warn("Division by 0. 0 assumed.");
+			      resultP->X_add_number = 0;
+			    }
+			  break;
+
+			case O_bit_and:
+			  resultP->X_add_number &= right . X_add_number;
+			  break;
+
+			case O_multiply:
+			  resultP->X_add_number *= right . X_add_number;
+			  break;
+
+			case O_divide:
+			  if (right . X_add_number)
+			    {
+			      resultP->X_add_number /= right . X_add_number;
+			    }
+			  else
+			    {
+			      as_warn("Division by 0. 0 assumed.");
+			      resultP->X_add_number = 0;
+			    }
+			  break;
+
+			case O_left_shift:
+			  resultP->X_add_number <<= right . X_add_number;
+			  break;
+
+			case O_right_shift:
+			  resultP->X_add_number >>= right . X_add_number;
+			  break;
+
+			case O_bit_exclusive_or:
+			  resultP->X_add_number ^= right . X_add_number;
+			  break;
+
+			case O_bit_or_not:
+			  resultP->X_add_number |= ~ right . X_add_number;
+			  break;
+
+			default:
+			  BAD_CASE(op_left);
+			  break;
+			} /* switch(operator) */
+		    }
+		}		/* If we have to force need_pass_2. */
+	    }			/* If operator was +. */
+	}			/* If we didn't set need_pass_2. */
+      op_left = op_right;
+    }				/* While next operator is >= this rank. */
+  return (resultP->X_seg);
+}
+
+/*
+ *			get_symbol_end()
+ *
+ * This lives here because it belongs equally in expr.c & read.c.
+ * Expr.c is just a branch office read.c anyway, and putting it
+ * here lessens the crowd at read.c.
+ *
+ * Assume input_line_pointer is at start of symbol name.
+ * Advance input_line_pointer past symbol name.
+ * Turn that character into a '\0', returning its former value.
+ * This allows a string compare (RMS wants symbol names to be strings)
+ * of the symbol name.
+ * There will always be a char following symbol name, because all good
+ * lines end in end-of-line.
+ */
+char
+get_symbol_end()
+{
+  register char c;
+
+  while (is_part_of_name(c = * input_line_pointer ++))
+    ;
+  * -- input_line_pointer = 0;
+  return (c);
+}
+
+/*
+ * Local Variables:
+ * comment-column: 0
+ * fill-column: 131
+ * End:
+ */
+
+/* end: expr.c */