fix Xtensa branch relaxation bug

[Bob Wilson <bwilson at tensilica dot com>]

The MAX_IMMED6 macro used to determine if a short Xtensa branch is in range had 
an incorrect value that caused the assembler to hit an assertion failure.  I've 
included a new test for this.  Committed on mainline.

gas/
        * config/tc-xtensa.c (MAX_IMMED6): Change value to 65.

gas/testsuite/
        * gas/xtensa/short_branch_offset.s: New.
        * gas/xtensa/short_branch_offset.d: New.
        * gas/xtensa/all.exp: Run new test.

Index: config/tc-xtensa.c
===================================================================
RCS file: /cvs/src/src/gas/config/tc-xtensa.c,v
retrieving revision 1.16
diff -u -r1.16 tc-xtensa.c
--- config/tc-xtensa.c	10 Nov 2004 22:20:27 -0000	1.16
+++ config/tc-xtensa.c	11 Nov 2004 19:01:30 -0000
@@ -7242,8 +7242,11 @@
    use for alignment narrow branches that definitely will not expand to a
    jump and a branch.  These functions find and mark these cases.  */
 
-/* the range in bytes of a bnez.n and beqz.n */
-#define MAX_IMMED6 68
+/* The range in bytes of BNEZ.N and BEQZ.N.  The target operand is encoded
+   as PC + 4 + imm6, where imm6 is a 6-bit immediate ranging from 0 to 63.
+   We start counting beginning with the frag after the 2-byte branch, so the
+   maximum offset is (4 - 2) + 63 = 65.  */
+#define MAX_IMMED6 65
 
 static size_t unrelaxed_frag_max_size (fragS *);
 
Index: testsuite/gas/xtensa/all.exp
===================================================================
RCS file: /cvs/src/src/gas/testsuite/gas/xtensa/all.exp,v
retrieving revision 1.2
diff -u -r1.2 all.exp
--- testsuite/gas/xtensa/all.exp	8 Oct 2004 00:22:12 -0000	1.2
+++ testsuite/gas/xtensa/all.exp	11 Nov 2004 19:01:30 -0000
@@ -78,9 +78,9 @@
     objdump_finish
     if [all_ones $x1] then { pass $testname } else { fail $testname }
 
-
+    run_dump_test "short_branch_offset"
 }
 
 if [info exists errorInfo] then {
     unset errorInfo
-    }
+}
Index: testsuite/gas/xtensa/short_branch_offset.d
===================================================================
RCS file: testsuite/gas/xtensa/short_branch_offset.d
diff -N testsuite/gas/xtensa/short_branch_offset.d
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gas/xtensa/short_branch_offset.d	11 Nov 2004 19:01:30 -0000
@@ -0,0 +1,34 @@
+# as: --no-target-align
+# objdump: -d
+
+# Test that a short branch with a target just barely out of range does
+# not crash the assembler.
+
+.*: +file format elf32-xtensa-.*
+
+Disassembly of section .text:
+
+00000000 <.text>:
+   0:	.*        	bnez	a2, 0x45
+   3:	.*        	nop
+   6:	.*        	nop
+   9:	.*        	nop
+   c:	.*        	nop
+   f:	.*        	nop
+  12:	.*        	nop
+  15:	.*        	nop
+  18:	.*        	nop
+  1b:	.*        	nop
+  1e:	.*        	nop
+  21:	.*        	nop
+  24:	.*        	nop
+  27:	.*        	nop
+  2a:	.*        	nop
+  2d:	.*        	nop
+  30:	.*        	nop
+  33:	.*        	nop
+  36:	.*        	nop
+  39:	.*        	nop
+  3c:	.*        	nop
+  3f:	.*        	nop
+  42:	.*        	nop
Index: testsuite/gas/xtensa/short_branch_offset.s
===================================================================
RCS file: testsuite/gas/xtensa/short_branch_offset.s
diff -N testsuite/gas/xtensa/short_branch_offset.s
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gas/xtensa/short_branch_offset.s	11 Nov 2004 19:01:30 -0000
@@ -0,0 +1,24 @@
+	bnez.n	a2, .Lplus68
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+	_nop
+.Lplus68: