Fix review comments

cranelift/codegen/meta/src/gen_legalizer.rs

@@ -89,6 +89,8 @@ fn unwrap_inst(
                     fmtln!(fmt, "func.dfg.resolve_aliases(args[{}]),", n);
                 } else if op.is_varargs() {
                     let n = inst.imm_opnums.iter().chain(inst.value_opnums.iter()).max().map(|n| n + 1).unwrap_or(0);
+                    // We need to create a `Vec` here, as using a slice would result in a borrowck
+                    // error later on.
                     fmtln!(fmt, "\
                         args.iter().skip({}).map(|&arg| func.dfg.resolve_aliases(arg)).collect::<Vec<_>>(),\
                     ", n);
@@ -115,6 +117,9 @@ fn unwrap_inst(
             let name = var_pool
                 .get(apply.args[i].maybe_var().expect("vararg without name"))
                 .name;
+
+            // Above name is set to an `Vec` representing the varargs. However it is expected to be
+            // `&[Value]` below, so we borrow it.
             fmtln!(fmt, "let {} = &{};", name, name);
         }
     }
@@ -419,6 +424,8 @@ fn gen_transform<'a>(
         }
 
         if transform.def_pool.get(transform.src).apply.inst.is_branch {
+            // A branch might have been legalized into multiple branches, so we need to recompute
+            // the cfg.
             fmt.line("cfg.recompute_ebb(pos.func, pos.current_ebb().unwrap());");
         }
 

cranelift/codegen/src/legalizer/mod.rs

@@ -75,12 +75,11 @@ fn legalize_inst(
         match pos.func.dfg.value_def(arg) {
             ir::ValueDef::Result(inst, _num) => {
                 if let ir::InstructionData::Binary {
-                    opcode, args: _, ..
+                    opcode: ir::Opcode::Iconcat,
+                    ..
                 } = pos.func.dfg[inst]
                 {
-                    if opcode != ir::Opcode::Iconcat {
-                        return LegalizeInstResult::SplitLegalizePending;
-                    }
+                    // `arg` was created by an `iconcat` instruction.
                 } else {
                     // `arg` was not created by an `iconcat` instruction. Don't try to resolve it,
                     // as otherwise `split::isplit` will re-insert the original `isplit`, causing
@@ -153,7 +152,9 @@ pub fn legalize_function(func: &mut ir::Function, cfg: &mut ControlFlowGraph, is
 
     // Process EBBs in layout order. Some legalization actions may split the current EBB or append
     // new ones to the end. We need to make sure we visit those new EBBs too.
-    while let Some(_ebb) = pos.next_ebb() {
+    while let Some(ebb) = pos.next_ebb() {
+        split::split_ebb_params(pos.func, cfg, ebb);
+
         // Keep track of the cursor position before the instruction being processed, so we can
         // double back when replacing instructions.
         let mut prev_pos = pos.position();
@@ -176,10 +177,6 @@ pub fn legalize_function(func: &mut ir::Function, cfg: &mut ControlFlowGraph, is
         }
     }
 
-    while let Some(ebb) = pos.next_ebb() {
-        split::split_ebb_params(pos.func, cfg, ebb);
-    }
-
     // Try legalizing `isplit` and `vsplit` instructions, which could not previously be legalized.
     for inst in pending_splits {
         pos.goto_inst(inst);