Add a trapff instruction.

This is the floating point equivalent of trapif: Trap when a given
condition is in the floating-point flags.

Define Intel encodings comparable to the trapif encodings.

lib/reader/src/parser.rs

@@ -2363,6 +2363,21 @@ impl<'a> Parser<'a> {
                     code,
                 }
             }
+            InstructionFormat::FloatCondTrap => {
+                let cond = self.match_enum("expected floatcc condition code")?;
+                let arg = self.match_value("expected SSA value operand")?;
+                self.match_token(
+                    Token::Comma,
+                    "expected ',' between operands",
+                )?;
+                let code = self.match_enum("expected trap code")?;
+                InstructionData::FloatCondTrap {
+                    opcode,
+                    cond,
+                    arg,
+                    code,
+                }
+            }
         };
         Ok(idata)
     }