C/C++ front-end: accept all floating-point extensions that GCC and Clang support

Testing with Compiler Explorer showed that Clang supports a subset of
GCC's extensions, and GCC also supports some more extensions that what
we previously covered.

Author: tautschnig

regression/ansi-c/float_constant1/main.c

@@ -21,9 +21,21 @@ STATIC_ASSERT(__builtin_types_compatible_p(_Float64, __typeof(1.0f64)));
 STATIC_ASSERT(__builtin_types_compatible_p(_Float128, __typeof(1.0f128)));
 STATIC_ASSERT(__builtin_types_compatible_p(_Float32x, __typeof(1.0f32x)));
 STATIC_ASSERT(__builtin_types_compatible_p(_Float64x, __typeof(1.0f64x)));
+// f128x should be supported by GCC >= 7 (and for C++ in GCC >=13), but there
+// are not current GCC ports that actually support such types
 STATIC_ASSERT(__builtin_types_compatible_p(_Float128x, __typeof(1.0f128x)));
 #endif
 
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ >= 13
+STATIC_ASSERT(__builtin_types_compatible_p(_Float16, __typeof(1.0f16)));
+STATIC_ASSERT(__builtin_types_compatible_p(__bf16, __typeof(1.0bf16)));
+STATIC_ASSERT(__builtin_types_compatible_p(__bf16, __typeof(1.BF16)));
+#endif
+
+#if defined(__clang__) && __clang_major__ >= 6
+STATIC_ASSERT(__builtin_types_compatible_p(_Float16, __typeof(1.0f16)));
+#endif
+
 #ifdef __GNUC__
 _Complex c;
 #endif

src/ansi-c/literals/parse_float.cpp

@@ -77,8 +77,8 @@ parse_floatt::parse_floatt(const std::string &src)
       p++;
 
     // get exponent
-    while(*p!=0 && *p!='f' && *p!='l' &&
-          *p!='w' && *p!='q' && *p!='d')
+    while(*p != 0 && *p != 'f' && *p != 'l' && *p != 'w' && *p != 'q' &&
+          *p != 'd' && *p != 'b')
     {
       str_exponent+=*p;
       p++;
@@ -121,10 +121,8 @@ parse_floatt::parse_floatt(const std::string &src)
       p++;
 
     // get fraction part
-    while(*p!=0 && *p!='e' &&
-          *p!='f' && *p!='l' &&
-          *p!='w' && *p!='q' && *p!='d' &&
-          *p!='i' && *p!='j')
+    while(*p != 0 && *p != 'e' && *p != 'f' && *p != 'l' && *p != 'w' &&
+          *p != 'q' && *p != 'd' && *p != 'i' && *p != 'j' && *p != 'b')
     {
       str_fraction_part+=*p;
       p++;
@@ -139,9 +137,8 @@ parse_floatt::parse_floatt(const std::string &src)
       p++;
 
     // get exponent
-    while(*p!=0 && *p!='f' && *p!='l' &&
-          *p!='w' && *p!='q' && *p!='d' &&
-          *p!='i' && *p!='j')
+    while(*p != 0 && *p != 'f' && *p != 'l' && *p != 'w' && *p != 'q' &&
+          *p != 'd' && *p != 'i' && *p != 'j' && *p != 'b')
     {
       str_exponent+=*p;
       p++;
@@ -173,7 +170,7 @@ parse_floatt::parse_floatt(const std::string &src)
   is_float80=false;
   is_float128=is_float128x=false;
 
-  if(strcmp(p, "f16")==0)
+  if(strcmp(p, "f16") == 0 || strcmp(p, "bf16") == 0)
     is_float16=true;
   else if(strcmp(p, "f32")==0)
     is_float32=true;

src/ansi-c/scanner.l

@@ -217,10 +217,13 @@ hexfloat1       "0"[xX]{hexdigit}*"."{hexdigit}+[pP][+-]?{integer}
 hexfloat2       "0"[xX]{hexdigit}*"."[pP][+-]?{integer}
 hexfloat3       "0"[xX]{hexdigit}*[pP][+-]?{integer}
 float_suffix    [fFlLiIjJ]*
-gcc_ext_float_suffix    [wWqQ]|[dD][fFdDlL]?|"f16"|"f32"|"f64"|"f128"|"f32x"|"f64x"|"f128x"
+clang_ext_float_suffix [qQ]|"f16"|"F16"
+gcc_ext_float_width (("bf"|"BF")"16")|([fF]("32"|"64"|"128"|"32x"|"64x"|"128x"))
+gcc_ext_float_suffix {clang_ext_float_suffix}|[wW]|[dD][fFdDlL]?|{gcc_ext_float_width}
 float           {float1}|{float2}|{float3}|{hexfloat1}|{hexfloat2}|{hexfloat3}
 float_s         {float}{float_suffix}|{integer}[fF]
 gcc_ext_float_s {float}{gcc_ext_float_suffix}
+clang_ext_float_s {float}{clang_ext_float_suffix}
 cppstart        {ws}"#"{ws}
 cpplineno       {cppstart}"line"*{ws}{integer}{ws}.*{newline}
 cppdirective    {cppstart}({newline}|[^p].*|"p"[^r].*|"pr"[^a].*|"pra"[^g].*|"prag"[^m].*|"pragm"[^a].*)
@@ -1561,6 +1564,18 @@ __decltype          { if(PARSER.cpp98 &&
                   return TOK_INTEGER;
                 }
 
+{clang_ext_float_s} { if(PARSER.mode!=configt::ansi_ct::flavourt::GCC &&
+                         PARSER.mode != configt::ansi_ct::flavourt::CLANG)
+                      {
+                        yyansi_cerror("Preprocessor directive found");
+                        return TOK_SCANNER_ERROR;
+                      }
+                      newstack(yyansi_clval);
+                      parser_stack(yyansi_clval)=convert_float_literal(yytext);
+                      PARSER.set_source_location(parser_stack(yyansi_clval));
+                      return TOK_FLOATING;
+                    }
+
 {gcc_ext_float_s} { if(PARSER.mode!=configt::ansi_ct::flavourt::GCC)
                     {
                       yyansi_cerror("Preprocessor directive found");