better vcode printing

cranelift/codegen/src/machinst/vcode.rs

@@ -758,6 +758,7 @@ impl<I: VCodeInst> VCode<I> {
     {
         // To write into disasm string.
         use core::fmt::Write;
+        let want_disasm = true;
 
         let _tt = timing::vcode_emit();
         let mut buffer = MachBuffer::new();
@@ -1323,12 +1324,39 @@ impl<I: VCodeInst> fmt::Debug for VCode<I> {
 
         for block in 0..self.num_blocks() {
             let block = BlockIndex::new(block);
-            writeln!(f, "Block {}:", block.index())?;
+            write!(f, "Block {}(", block.index())?;
+            {
+                let mut first = true;
+                for vreg in self.block_params(block) {
+                    if !first {
+                        write!(f, ", ")?;
+                    } else {
+                        first = false;
+                    }
+                    write!(f, "{}", vreg)?;
+                }
+            }
+            writeln!(f, "):")?;
             if let Some(bb) = self.bindex_to_bb(block) {
                 writeln!(f, "    (original IR block: {})", bb)?;
             }
-            for succ in self.succs(block) {
-                writeln!(f, "    (successor: Block {})", succ.index())?;
+            for (i, succ) in self.succs(block).iter().enumerate() {
+                let last_inst = self.block_insns(block).last();
+                if self.is_branch(last_inst) {
+                    write!(f, "    (successor: Block {}(", succ.index())?;
+                    let mut first = true;
+                    for vreg in self.branch_blockparams(block, last_inst, i) {
+                        if !first {
+                            write!(f, ", ")?;
+                        } else {
+                            first = false;
+                        }
+                        write!(f, "{}", vreg)?;
+                    }
+                    writeln!(f, "))")?;
+                } else {
+                    write!(f, "    (successor: Block {})", succ.index())?;
+                }
             }
             let (start, end) = self.block_ranges[block.index()];
             writeln!(