Fix Invalid Instruction format in fuzzgen

cranelift/codegen/meta/src/gen_inst.rs

@@ -902,6 +902,9 @@ fn gen_format_constructor(format: &InstructionFormat, fmt: &mut Formatter) {
             fmtln!(fmt, "data.sign_extend_immediates(ctrl_typevar);");
         }
 
+        // Assert that this opcode belongs to this format
+        fmtln!(fmt, "assert_eq!(opcode.format(), InstructionFormat::from(&data), \"Wrong InstructionFormat for Opcode: {}\", opcode);");
+
         fmt.line("self.build(data, ctrl_typevar)");
     });
     fmtln!(fmt, "}");

cranelift/codegen/src/ir/builder.rs

@@ -4,6 +4,7 @@
 //! function. Many of its methods are generated from the meta language instruction definitions.
 
 use crate::ir;
+use crate::ir::instructions::InstructionFormat;
 use crate::ir::types;
 use crate::ir::{DataFlowGraph, InstructionData};
 use crate::ir::{Inst, Opcode, Type, Value};
@@ -217,7 +218,7 @@ mod tests {
     use crate::cursor::{Cursor, FuncCursor};
     use crate::ir::condcodes::*;
     use crate::ir::types::*;
-    use crate::ir::{Function, InstBuilder, ValueDef};
+    use crate::ir::{Function, InstBuilder, Opcode, TrapCode, ValueDef};
 
     #[test]
     fn types() {
@@ -262,4 +263,17 @@ mod tests {
         assert!(iadd != iconst);
         assert_eq!(pos.func.dfg.value_def(v0), ValueDef::Result(iconst, 0));
     }
+
+    #[test]
+    #[should_panic]
+    fn panics_when_inserting_wrong_opcode() {
+        let mut func = Function::new();
+        let block0 = func.dfg.make_block();
+        let mut pos = FuncCursor::new(&mut func);
+        pos.insert_block(block0);
+
+        // We are trying to create a Opcode::Return with the InstData::Trap, which is obviously wrong
+        pos.ins()
+            .Trap(Opcode::Return, I32, TrapCode::BadConversionToInteger);
+    }
 }

cranelift/fuzzgen/src/function_generator.rs

@@ -1,7 +1,8 @@
-use crate::codegen::ir::{ArgumentExtension, ArgumentPurpose, ValueList};
+use crate::codegen::ir::{ArgumentExtension, ArgumentPurpose};
 use crate::config::Config;
 use anyhow::Result;
 use arbitrary::{Arbitrary, Unstructured};
+use cranelift::codegen::ir::instructions::InstructionFormat;
 use cranelift::codegen::ir::{types::*, FuncRef, LibCall, UserExternalName, UserFuncName};
 use cranelift::codegen::ir::{
     AbiParam, Block, ExternalName, Function, JumpTable, Opcode, Signature, StackSlot, Type, Value,
@@ -24,11 +25,11 @@ fn insert_opcode(
     args: &'static [Type],
     rets: &'static [Type],
 ) -> Result<()> {
-    let mut arg_vals = ValueList::new();
+    let mut vals = Vec::with_capacity(args.len());
     for &arg in args.into_iter() {
         let var = fgen.get_variable_of_type(arg)?;
         let val = builder.use_var(var);
-        arg_vals.push(val, &mut builder.func.dfg.value_lists);
+        vals.push(val);
     }
 
     // For pretty much every instruction the control type is the return type
@@ -42,7 +43,16 @@ fn insert_opcode(
     .copied()
     .unwrap_or(INVALID);
 
-    let (inst, dfg) = builder.ins().MultiAry(opcode, ctrl_type, arg_vals);
+    // Choose the appropriate instruction format for this opcode
+    let (inst, dfg) = match opcode.format() {
+        InstructionFormat::NullAry => builder.ins().NullAry(opcode, ctrl_type),
+        InstructionFormat::Unary => builder.ins().Unary(opcode, ctrl_type, vals[0]),
+        InstructionFormat::Binary => builder.ins().Binary(opcode, ctrl_type, vals[0], vals[1]),
+        InstructionFormat::Ternary => builder
+            .ins()
+            .Ternary(opcode, ctrl_type, vals[0], vals[1], vals[2]),
+        _ => unimplemented!(),
+    };
     let results = dfg.inst_results(inst).to_vec();
 
     for (val, &ty) in results.into_iter().zip(rets) {