adjustments to floating-point printing

Ghidra/Features/Decompiler/src/decompile/cpp/float.cc

@@ -71,6 +71,7 @@ FloatFormat::FloatFormat(int4 sz)
     jbitimplied = true;
   }
   maxexponent = (1<<exp_size)-1;
+  calcPrecision();
 }
 
 /// \param sign is set to \b true if the value should be negative
@@ -227,6 +228,13 @@ uintb FloatFormat::getNaNEncoding(bool sgn) const
   return setSign(res,sgn);
 }
 
+void FloatFormat::calcPrecision(void)
+
+{
+  float val = frac_size * 0.30103;
+  decimal_precision = (int4)floor(val + 0.5);
+}
+
 /// \param encoding is the encoding value
 /// \param type points to the floating-point class, which is passed back
 /// \return the equivalent double value
@@ -613,4 +621,5 @@ void FloatFormat::restoreXml(const Element *el)
   }
   jbitimplied = xml_readbool(el->getAttributeValue("jbitimplied"));
   maxexponent = (1<<exp_size)-1;
+  calcPrecision();
 }

Ghidra/Features/Decompiler/src/decompile/cpp/float.hh

@@ -46,6 +46,7 @@ private:
   int4 exp_size;		///< Number of bits in exponent
   int4 bias;			///< What to add to real exponent to get encoding
   int4 maxexponent;		///< Maximum possible exponent
+  int4 decimal_precision;	///< Number of decimal digits of precision
   bool jbitimplied;		///< Set to \b true if integer bit of 1 is assumed
   static double createFloat(bool sign,uintb signif,int4 exp);	 ///< Create a double given sign, fractional, and exponent
   static floatclass extractExpSig(double x,bool *sgn,uintb *signif,int4 *exp);
@@ -55,12 +56,14 @@ private:
   uintb getZeroEncoding(bool sgn) const;			///< Get an encoded zero value
   uintb getInfinityEncoding(bool sgn) const;			///< Get an encoded infinite value
   uintb getNaNEncoding(bool sgn) const;				///< Get an encoded NaN value
+  void calcPrecision(void);					///< Calculate the decimal precision of this format
 public:
   FloatFormat(void) {}	///< Construct for use with restoreXml()
   FloatFormat(int4 sz);	///< Construct default IEEE 754 standard settings
   int4 getSize(void) const { return size; }			///< Get the size of the encoding in bytes
   double getHostFloat(uintb encoding,floatclass *type) const;	///< Convert an encoding into host's double
   uintb getEncoding(double host) const;				///< Convert host's double into \b this encoding
+  int4 getDecimalPrecision(void) const { return decimal_precision; }	///< Get number of digits of precision
   uintb convertEncoding(uintb encoding,const FloatFormat *formin) const;	///< Convert between two different formats
 
   uintb extractFractionalCode(uintb x) const;			///< Extract the fractional part of the encoding

Ghidra/Features/Decompiler/src/decompile/cpp/printc.cc

@@ -1087,38 +1087,59 @@ void PrintC::push_integer(uintb val,int4 sz,bool sign,
 /// \param op is the PcodeOp using the value
 void PrintC::push_float(uintb val,int4 sz,const Varnode *vn,const PcodeOp *op)
 {
-  ostringstream t;
+  string token;
 
   const FloatFormat *format = glb->translate->getFloatFormat(sz);
   if (format == (const FloatFormat *)0) {
-    t << "FLOAT_UNKNOWN";
+    token = "FLOAT_UNKNOWN";
   }
   else {
     FloatFormat::floatclass type;
     double floatval = format->getHostFloat(val,&type);
     if (type == FloatFormat::infinity) {
       if (format->extractSign(val))
-	t << '-';
-      t << "INFINITY";
+	token = "-INFINITY";
+      else
+	token = "INFINITY";
     }
     else if (type == FloatFormat::nan) {
       if (format->extractSign(val))
-	t << '-';
-      t << "NAN";
+	token = "-NAN";
+      else
+	token = "NAN";
     }
     else {
-      if ((mods & force_scinote)!=0)
+      ostringstream t;
+      if ((mods & force_scinote)!=0) {
 	t.setf( ios::scientific ); // Set to scientific notation
-      else
-	t.setf( ios::fixed );	// Otherwise use fixed notation
-      t.precision(8);		// Number of digits of precision
+	t.precision(format->getDecimalPrecision()-1);
 	t << floatval;
+	token = t.str();
+      }
+      else {
+	// Try to print "minimal" accurate representation of the float
+	t.unsetf( ios::floatfield );	// Use "default" notation
+	t.precision(format->getDecimalPrecision());
+	t << floatval;
+	token = t.str();
+	bool looksLikeFloat = false;
+	for(int4 i=0;i<token.size();++i) {
+	  char c = token[i];
+	  if (c == '.' || c == 'e') {
+	    looksLikeFloat = true;
+	    break;
+	  }
+	}
+	if (!looksLikeFloat) {
+	  token += ".0";	// Force token to look like a floating-point value
+	}
+      }
     }
   }
   if (vn==(const Varnode *)0)
-    pushAtom(Atom(t.str(),syntax,EmitXml::const_color,op));
+    pushAtom(Atom(token,syntax,EmitXml::const_color,op));
   else
-    pushAtom(Atom(t.str(),vartoken,EmitXml::const_color,op,vn));
+    pushAtom(Atom(token,vartoken,EmitXml::const_color,op,vn));
 }
 
 void PrintC::printUnicode(ostream &s,int4 onechar) const