From 5a4dcfb367b6d6bb37d8be199db97085a932a2ea Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Fri, 5 Mar 2021 14:28:18 +0100
Subject: [PATCH] builder: add support for -opt=0

This optimization level wasn't working before because some passes expect
some globals to be cleaned up afterwards. Cleaning these globals is
easy, just add the pass necessary for it. This shouldn't reduce the
usefulness of the -opt=0 build flag as most optimizations are still
skipped.
---
 Makefile               |  2 ++
 builder/build.go       | 11 ++---------
 transform/optimizer.go |  6 ++++++
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/Makefile b/Makefile
index aebf6354..98ff2ede 100644
--- a/Makefile
+++ b/Makefile
@@ -391,6 +391,8 @@ endif
 	@$(MD5SUM) test.hex
 	$(TINYGO) build             -o test.nro -target=nintendoswitch      examples/serial
 	@$(MD5SUM) test.nro
+	$(TINYGO) build -size short -o test.hex -target=pca10040 -opt=0     ./testdata/stdlib.go
+	@$(MD5SUM) test.hex
 
 wasmtest:
 	$(GO) test ./tests/wasm
diff --git a/builder/build.go b/builder/build.go
index bdeccad5..e5977770 100644
--- a/builder/build.go
+++ b/builder/build.go
@@ -411,15 +411,8 @@ func compileWholeProgram(pkgName string, config *compileopts.Config, compilerCon
 	// exactly.
 	errs = nil
 	switch config.Options.Opt {
-	/*
-		Currently, turning optimizations off causes compile failures.
-		We rely on the optimizer removing some dead symbols.
-		Avoid providing an option that does not work right now.
-		In the future once everything has been fixed we can re-enable this.
-
-		case "none", "0":
-			errs = transform.Optimize(mod, config, 0, 0, 0) // -O0
-	*/
+	case "none", "0":
+		errs = transform.Optimize(mod, config, 0, 0, 0) // -O0
 	case "1":
 		errs = transform.Optimize(mod, config, 1, 0, 0) // -O1
 	case "2":
diff --git a/transform/optimizer.go b/transform/optimizer.go
index dc9e1ffb..e330d1af 100644
--- a/transform/optimizer.go
+++ b/transform/optimizer.go
@@ -111,6 +111,12 @@ func Optimize(mod llvm.Module, config *compileopts.Config, optLevel, sizeLevel i
 		if len(errs) > 0 {
 			return errs
 		}
+
+		// Clean up some leftover symbols of the previous transformations.
+		goPasses := llvm.NewPassManager()
+		defer goPasses.Dispose()
+		goPasses.AddGlobalDCEPass()
+		goPasses.Run(mod)
 	}
 
 	// Lower async implementations.