[PATCH] sim: avoid shadowing vars when decoding insns

[Mike Frysinger <vapier@gentoo.org>]

When generating switch decode tables, the switch statements all use
the same variable name "val".  This causes nested switches to shadow
earlier ones.  Use the existing "switch-num" to generate unique names
when nesting since it's otherwise unused.

Previously we'd have:

...
    {
      unsigned int val = (((insn >> 4) & (255 << 0)));
      switch (val)
      {
...
      case 15 :
        {
          unsigned int val = (((insn >> 12) & (15 << 0)));
          switch (val)
          {
...

Leading to:
.../sim/cris/decodev10.c: In function ‘crisv10f_decode’:
.../sim/cris/decodev10.c:351:24: error: declaration of ‘val’ shadows a previous local [-Werror=shadow=compatible-local]
  351 |           unsigned int val = (((insn >> 12) & (15 << 0)));
      |                        ^~~
.../sim/cris/decodev10.c:331:20: note: shadowed declaration is here
  331 |       unsigned int val = (((insn >> 4) & (255 << 0)));
      |                    ^~~

Now we have:
...
    {
      unsigned int val0 = (((insn >> 4) & (255 << 0)));
      switch (val0)
      {
...
      case 15 :
        {
          unsigned int val1 = (((insn >> 12) & (15 << 0)));
          switch (val1)
          {
...
---
 utils-sim.scm | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/utils-sim.scm b/utils-sim.scm
index 07d776d286d8..dca0f0705036 100644
--- a/utils-sim.scm
+++ b/utils-sim.scm
@@ -995,8 +995,8 @@
 )
 
 ; Generate switch statement to decode TABLE-GUTS.
-; SWITCH-NUM is for compatibility with the computed goto decoder and
-; isn't used.
+; SWITCH-NUM is for compatibility with the computed goto decoder and tracks the
+; nesting depth.
 ; STARTBIT is the bit offset of the instruction value that C variable `insn'
 ; holds (note that this is independent of LSB0?).
 ; DECODE-BITSIZE is the number of bits of the insn that `insn' holds.
@@ -1017,7 +1017,8 @@
 			     table-guts table-guts-thus-far
 			     indent lsb0? invalid-insn fn?)
 
-  (let ((new-table-guts-thus-far (append table-guts-thus-far (list table-guts))))
+  (let ((new-table-guts-thus-far (append table-guts-thus-far (list table-guts)))
+        (varname (string-append "val" (number->string switch-num))))
 
     (string-list
      indent "{\n"
@@ -1027,19 +1028,19 @@
 	   (set! startbit (dtable-guts-startbit table-guts))
 	   (set! decode-bitsize (dtable-guts-bitsize table-guts))
 	 ;; FIXME: Bits may get fetched again during extraction.
-	   (string-append indent "  unsigned int val;\n"
+	   (string-append indent "  unsigned int " varname ";\n"
 			  indent "  /* Must fetch more bits.  */\n"
 			  indent "  insn = "
 			  (gen-ifetch "pc" startbit decode-bitsize)
 			  ";\n"
-			  indent "  val = "))
-	 (string-append indent "  unsigned int val = "))
+			  indent "  " varname " = "))
+	 (string-append indent "  unsigned int " varname " = "))
      (/gen-decode-bits (dtable-guts-bitnums table-guts)
 		       (dtable-guts-startbit table-guts)
 		       (dtable-guts-bitsize table-guts)
 		       "insn" "entire_insn" lsb0?)
      ";\n"
-     indent "  switch (val)\n"
+     indent "  switch (" varname ")\n"
      indent "  {\n"
 
      ;; The code is more readable, and icache use is improved, if we collapse
@@ -1067,7 +1068,7 @@
 		     (/gen-decode-expr-entry (car entries) indent invalid-insn fn?))
 		    ((table)
 		     (/gen-decode-table-entry (car entries) (cdr entries)
-					      switch-num startbit decode-bitsize
+					      (+ switch-num 1) startbit decode-bitsize
 					      new-table-guts-thus-far
 					      indent lsb0? invalid-insn fn?))
 		    )
@@ -1105,7 +1106,7 @@
 
     ; Now print it out.
 
-    (/gen-decoder-switch "0" 0 decode-bitsize
+    (/gen-decoder-switch 0 0 decode-bitsize
 			 table-guts nil
 			 indent lsb0? invalid-insn fn?))
 )
-- 
2.43.0