Reduce number of unreachable instructions

Author: willemneal

src/compiler.ts

@@ -9230,7 +9230,7 @@ export class Compiler extends DiagnosticEmitter {
     const getArg = (i: i32): ExpressionRef => module.local_get(i, Type.i32.toNativeType());
     // Condition to switch on
     const first = relooper.addBlockWithSwitch(module.nop(), getArg(0));
-    const zero = relooper.addBlock(module.drop(module.i32(0)));
+    const zero = relooper.addBlock(module.nop());
 
     for (let index: i32 = 0; index < iFuncs.length; index++) {
       const [funcID, classes] = iFuncs[index];
@@ -9246,15 +9246,15 @@ export class Compiler extends DiagnosticEmitter {
         const condition = module.binary(BinaryOp.EqI32, getArg(1), module.i32(classID));
         relooper.addBranch(innerBlock, methodCase, condition);
       }
-      relooper.addBranch(innerBlock, zero, 0, module.unreachable());
+      relooper.addBranch(innerBlock, zero);
     }
-    relooper.addBranchForSwitch(first, zero, [], module.unreachable());
+    relooper.addBranchForSwitch(first, zero, []);
 
     var typeRef = this.ensureFunctionType([Type.u32, Type.u32], Type.u32, null);
 
     const body = module.block(
       null,
-      [relooper.renderAndDispose(first, 0), module.i32(0)],
+      [relooper.renderAndDispose(first, 0), module.unreachable(), module.i32(0)],
       Type.u32.toNativeType()
     );
     const hardCoded = this.module.i32(1);

tests/compiler.js

@@ -135,7 +135,7 @@ tests.forEach(filename => {
   var cmd = [
     filename,
     "--baseDir", basedir,
-    // "--validate",
+    "--validate",
     "--measure",
     "--debug",
     "--textFile" // -> stdout

tests/compiler/interface.optimized.wat

@@ -163,11 +163,11 @@
   i32.add
  )
  (func $~virtual (; 7 ;) (type $FUNCSIG$iii) (param $0 i32) (param $1 i32) (result i32)
-  block $switch$1$default
+  block $block$2$break
    block $switch$1$case$6
     block $switch$1$case$3
      local.get $0
-     br_table $switch$1$case$3 $switch$1$case$6 $switch$1$default
+     br_table $switch$1$case$3 $switch$1$case$6 $block$2$break
     end
     local.get $1
     i32.const 3
@@ -178,14 +178,10 @@
     else
      local.get $1
      i32.const 4
-     i32.eq
-     if
-      i32.const 2
-      return
-     else
-      unreachable
-     end
-     unreachable
+     i32.ne
+     br_if $block$2$break
+     i32.const 2
+     return
     end
     unreachable
    end
@@ -202,12 +198,8 @@
     if
      i32.const 4
      return
-    else
-     unreachable
     end
-    unreachable
    end
-   unreachable
   end
   unreachable
  )

tests/compiler/interface.untouched.wat

@@ -288,7 +288,7 @@
        i32.const 2
        return
       else
-       unreachable
+       br $block$2$break
       end
       unreachable
      end
@@ -308,17 +308,15 @@
       i32.const 4
       return
      else
-      unreachable
+      br $block$2$break
      end
      unreachable
     end
     unreachable
    end
-   unreachable
+   br $block$2$break
   end
-  i32.const 0
-  drop
-  i32.const 0
+  unreachable
  )
  (func $null (; 17 ;) (type $FUNCSIG$v)
  )