interp: keep reverted package initializers in order

Previously, a package initializer that could not be reverted correctly
would be called at runtime. But the initializer would be called in the
wrong order: after later packages are initialized.

This commit fixes this oversight and adds a test to verify the new
behavior.

interp/interp.go

@@ -110,17 +110,19 @@ func Run(mod llvm.Module, debug bool) error {
 			fmt.Fprintln(os.Stderr, "call:", fn.Name())
 		}
 		_, mem, callErr := r.run(r.getFunction(fn), nil, nil, "    ")
+		call.EraseFromParentAsInstruction()
 		if callErr != nil {
 			if isRecoverableError(callErr.Err) {
 				if r.debug {
 					fmt.Fprintln(os.Stderr, "not interpreting", r.pkgName, "because of error:", callErr.Error())
 				}
 				mem.revert()
+				i8undef := llvm.Undef(r.i8ptrType)
+				r.builder.CreateCall(fn, []llvm.Value{i8undef, i8undef}, "")
 				continue
 			}
 			return callErr
 		}
-		call.EraseFromParentAsInstruction()
 		for index, obj := range mem.objects {
 			r.objects[index] = obj
 		}

interp/interp_test.go

@@ -17,6 +17,7 @@ func TestInterp(t *testing.T) {
 		"slice-copy",
 		"consteval",
 		"interface",
+		"revert",
 	} {
 		name := name // make tc local to this closure
 		t.Run(name, func(t *testing.T) {

interp/testdata/revert.ll

@@ -0,0 +1,21 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+declare void @externalCall(i64)
+
+define void @runtime.initAll() unnamed_addr {
+entry:
+  call void @foo.init(i8* undef, i8* undef)
+  call void @main.init(i8* undef, i8* undef)
+  ret void
+}
+
+define internal void @foo.init(i8* %context, i8* %parentHandle) unnamed_addr {
+  unreachable ; this triggers a revert of @foo.init.
+}
+
+define internal void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  call void @externalCall(i64 3)
+  ret void
+}

interp/testdata/revert.out.ll

@@ -0,0 +1,15 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+declare void @externalCall(i64) local_unnamed_addr
+
+define void @runtime.initAll() unnamed_addr {
+entry:
+  call fastcc void @foo.init(i8* undef, i8* undef)
+  call void @externalCall(i64 3)
+  ret void
+}
+
+define internal fastcc void @foo.init(i8* %context, i8* %parentHandle) unnamed_addr {
+  unreachable
+}