Patch to elide sign compare warning in ?:

["Kaveh R. Ghazi" <ghazi at caip dot rutgers dot edu>]

We already eliminate sign compare warnings for "(unsigned) > 64".
This patch eliminates the sign compare warnings for these kinds of
expressions: "(unsigned) > (foo ? 64 : 32)"

This construct appears a lot on platforms like the sparc-solaris where
BIGGEST_ALIGNMENT is defined as (TARGET_ARCH64 ? 128 : 64), the sign
compare warnings are reduced from 227 to 56.  On a platform like
x86-linux where BIGGEST_ALIGNMENT is a constant, the gains are modest,
(something like 2.)

Okay to install?

		--Kaveh

PS: Alternate suggestions on what to call the tree_expr_unsigned_p
function would be appreciated.  I'm not sure the current name
accurately describes what is does.


2000-04-07  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>

	* tree.c (tree_expr_unsigned_p): New function.

	* tree.h (tree_expr_unsigned_p): Declare.

	* c-typeck.c (build_binary_op): Call `tree_expr_unsigned_p' to
	elide some sign_compare warnings.

cp:
	* typeck.c (build_binary_op): Call `tree_expr_unsigned_p' to elide
	some sign_compare warnings.


diff -rup orig/egcs-CVS20000405/gcc/tree.c egcs-CVS20000405/gcc/tree.c
--- orig/egcs-CVS20000405/gcc/tree.c	Mon Apr  3 22:20:32 2000
+++ egcs-CVS20000405/gcc/tree.c	Thu Apr  6 09:15:58 2000
@@ -4370,6 +4370,25 @@ tree_int_cst_sgn (t)
     return 1;
 }
 
+/* Return true if `t' is known to be unsigned.  */
+
+int
+tree_expr_unsigned_p (t)
+     tree t;
+{
+  switch (TREE_CODE (t))
+    {
+    case INTEGER_CST:
+      return tree_int_cst_sgn (t) >= 0;
+    case COND_EXPR:
+      return tree_expr_unsigned_p (TREE_OPERAND (t, 1))
+	&& tree_expr_unsigned_p (TREE_OPERAND (t, 2));
+    default:
+      /* We don't know sign of `t', so be safe and return false.  */
+      return 0;
+    }
+}
+
 /* Compare two constructor-element-type constants.  Return 1 if the lists
    are known to be equal; otherwise return 0.  */
 
diff -rup orig/egcs-CVS20000405/gcc/tree.h egcs-CVS20000405/gcc/tree.h
--- orig/egcs-CVS20000405/gcc/tree.h	Tue Apr  4 14:18:53 2000
+++ egcs-CVS20000405/gcc/tree.h	Thu Apr  6 08:55:48 2000
@@ -1697,6 +1697,7 @@ extern int host_integerp		PARAMS ((tree,
 extern HOST_WIDE_INT tree_low_cst	PARAMS ((tree, int));
 extern int tree_int_cst_msb		PARAMS ((tree));
 extern int tree_int_cst_sgn		PARAMS ((tree));
+extern int tree_expr_unsigned_p		PARAMS ((tree));
 extern int index_type_equal		PARAMS ((tree, tree));
 extern tree get_inner_array_type	PARAMS ((tree));
 
diff -rup orig/egcs-CVS20000405/gcc/c-typeck.c egcs-CVS20000405/gcc/c-typeck.c
--- orig/egcs-CVS20000405/gcc/c-typeck.c	Thu Mar 30 00:02:38 2000
+++ egcs-CVS20000405/gcc/c-typeck.c	Thu Apr  6 09:11:24 2000
@@ -2416,11 +2416,12 @@ build_binary_op (code, orig_op0, orig_op
 		  else
 		    sop = xop1, uop = xop0;
 
-		  /* Do not warn if the signed quantity is an unsuffixed
-		     integer literal (or some static constant expression
-		     involving such literals) and it is non-negative.  */
-		  if (TREE_CODE (sop) == INTEGER_CST
-		      && tree_int_cst_sgn (sop) >= 0)
+		  /* Do not warn if the signed quantity is an
+		     unsuffixed integer literal (or some static
+		     constant expression involving such literals or a
+		     conditional expression involving such literals)
+		     and it is non-negative.  */
+		  if (tree_expr_unsigned_p (sop))
 		    /* OK */;
 		  /* Do not warn if the comparison is an equality operation,
 		     the unsigned quantity is an integral constant, and it
diff -rup orig/egcs-CVS20000405/gcc/cp/typeck.c egcs-CVS20000405/gcc/cp/typeck.c
--- orig/egcs-CVS20000405/gcc/cp/typeck.c	Sun Mar 26 23:23:35 2000
+++ egcs-CVS20000405/gcc/cp/typeck.c	Thu Apr  6 09:13:20 2000
@@ -3960,11 +3960,10 @@ build_binary_op (code, orig_op0, orig_op
 	    /* OK */;
 	  /* Do not warn if the signed quantity is an unsuffixed
 	     integer literal (or some static constant expression
+	     involving such literals or a conditional expression
 	     involving such literals) and it is non-negative.  */
-	  else if ((op0_signed && TREE_CODE (orig_op0) == INTEGER_CST
-		    && tree_int_cst_sgn (orig_op0) >= 0)
-		   || (op1_signed && TREE_CODE (orig_op1) == INTEGER_CST
-		       && tree_int_cst_sgn (orig_op1) >= 0))
+	  else if ((op0_signed && tree_expr_unsigned_p (orig_op0))
+		   || (op1_signed && tree_expr_unsigned_p (orig_op1)))
 	    /* OK */;
 	  /* Do not warn if the comparison is an equality operation,
 	     the unsigned quantity is an integral constant and it does