Improve --varch error checking. (#394)

* Improve --varch error checking.

Print out why an option has problems.
Add check that elen must be >= xlen, flen, per the spec.
Since RV32G includes D by default, bump default elen to 64.

* Remove debug printf.

configure

@@ -1362,7 +1362,7 @@ Optional Packages:
   --without-PACKAGE       do not use PACKAGE (same as --with-PACKAGE=no)
   --with-isa=RV64IMAFDC   Sets the default RISC-V ISA
   --with-priv=MSU         Sets the default RISC-V privilege modes supported
-  --with-varch=v128:e32:s128
+  --with-varch=v128:e64:s128
                           Sets the default vector config
 
 Some influential environment variables:
@@ -4649,7 +4649,7 @@ _ACEOF
 else
 
 cat >>confdefs.h <<_ACEOF
-#define DEFAULT_VARCH "v128:e32:s128"
+#define DEFAULT_VARCH "v128:e64:s128"
 _ACEOF
 
 fi

riscv/processor.cc

@@ -68,9 +68,9 @@ static void bad_priv_string(const char* priv)
   abort();
 }
 
-static void bad_varch_string(const char* varch)
+static void bad_varch_string(const char* varch, const char *message)
 {
-  fprintf(stderr, "error: bad --varch option %s\n", varch);
+  fprintf(stderr, "error: bad --varch option %s: %s\n", varch, message);
   abort();
 }
 
@@ -80,9 +80,9 @@ static int parse_varch(std::string &str){
     std::string sval = str.substr(1);
     val = std::stoi(sval);
     if ((val & (val - 1)) != 0) // val should be power of 2
-      bad_varch_string(str.c_str());
+      bad_varch_string(str.c_str(), "must be a power of 2");
   }else{
-    bad_varch_string(str.c_str());
+    bad_varch_string(str.c_str(), "must not be empty");
   }
   return val;
 }
@@ -114,14 +114,24 @@ void processor_t::parse_varch_string(const char* s)
     }else if (token[0] == 's'){
       slen = parse_varch(token);
     }else{
-      bad_varch_string(str.c_str());
+      bad_varch_string(str.c_str(), "Unsupported token");
     }
     str.erase(0, pos + delimiter.length());
   }
 
-  if (!(vlen >= 32 || vlen <= 4096) && !(slen >= vlen || slen <= vlen) && !(elen >= slen || elen <= slen)){
-    bad_varch_string(s);
-  }
+  /* Vector spec requirements. */
+  if (vlen < elen)
+    bad_varch_string(s, "vlen must be >= elen");
+  if (vlen < slen)
+    bad_varch_string(s, "vlen must be >= slen");
+  if (slen < 32)
+    bad_varch_string(s, "slen must be >= 32");
+  if ((unsigned) elen < std::max(max_xlen, get_flen()))
+    bad_varch_string(s, "elen must be >= max(xlen, flen)");
+
+  /* spike requirements. */
+  if (vlen > 4096)
+    bad_varch_string(s, "vlen must be <= 4096");
 
   VU.VLEN = vlen;
   VU.ELEN = elen;

riscv/riscv.ac

@@ -13,10 +13,10 @@ AC_ARG_WITH(priv,
   AC_DEFINE_UNQUOTED([DEFAULT_PRIV], "MSU", [Default value for --priv switch]))
 
 AC_ARG_WITH(varch,
-	[AS_HELP_STRING([--with-varch=v128:e32:s128],
+	[AS_HELP_STRING([--with-varch=v128:e64:s128],
 		[Sets the default vector config])],
   AC_DEFINE_UNQUOTED([DEFAULT_VARCH], "$withval", [Default value for --varch switch]),
-  AC_DEFINE_UNQUOTED([DEFAULT_VARCH], "v128:e32:s128", [Default value for --varch switch]))
+  AC_DEFINE_UNQUOTED([DEFAULT_VARCH], "v128:e64:s128", [Default value for --varch switch]))
 
 
 AC_SEARCH_LIBS([dlopen], [dl dld], [], [