From c9ae72a10535383f91a8afb1ff9bf633d32592dd Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Mon, 24 Sep 2018 16:17:42 +0200
Subject: [PATCH] all: allow -O0 optimization level

---
 compiler/compiler.go   | 20 ++++++++------------
 src/runtime/runtime.go | 37 +++++++++++++++++--------------------
 2 files changed, 25 insertions(+), 32 deletions(-)

diff --git a/compiler/compiler.go b/compiler/compiler.go
index 48cfe0f8..e176523d 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -361,22 +361,18 @@ func (c *Compiler) Compile(mainPath string) error {
 	}
 	c.builder.CreateRetVoid()
 
-	// Adjust main function.
+	mainWrapper := c.mod.NamedFunction("runtime.mainWrapper")
+	block = c.ctx.AddBasicBlock(mainWrapper, "entry")
+	c.builder.SetInsertPointAtEnd(block)
 	realMain := c.mod.NamedFunction(c.ir.MainPkg().Pkg.Path() + ".main")
 	if c.ir.NeedsScheduler() {
-		c.mod.NamedFunction("runtime.main_mainAsync").ReplaceAllUsesWith(realMain)
+		coroutine := c.builder.CreateCall(realMain, []llvm.Value{llvm.ConstPointerNull(c.i8ptrType)}, "")
+		scheduler := c.mod.NamedFunction("runtime.scheduler")
+		c.builder.CreateCall(scheduler, []llvm.Value{coroutine}, "")
 	} else {
-		c.mod.NamedFunction("runtime.main_main").ReplaceAllUsesWith(realMain)
-	}
-
-	// Only use a scheduler when necessary.
-	if c.ir.NeedsScheduler() {
-		// Enable the scheduler.
-		hasScheduler := c.mod.NamedGlobal("runtime.hasScheduler")
-		hasScheduler.SetInitializer(llvm.ConstInt(llvm.Int1Type(), 1, false))
-		hasScheduler.SetGlobalConstant(true)
-		hasScheduler.SetUnnamedAddr(true)
+		c.builder.CreateCall(realMain, nil, "")
 	}
+	c.builder.CreateRetVoid()
 
 	// Initialize runtime type information, for interfaces.
 	// See src/runtime/interface.go for more details.
diff --git a/src/runtime/runtime.go b/src/runtime/runtime.go
index 5ac66633..25da2143 100644
--- a/src/runtime/runtime.go
+++ b/src/runtime/runtime.go
@@ -10,14 +10,18 @@ const Compiler = "tgo"
 // package.
 func initAll()
 
-// These signatures are used to call the correct main function: with scheduling
-// or without scheduling.
-func main_main()
-func main_mainAsync(parent *coroutine) *coroutine
-
-// The compiler will change this to true if there are 'go' statements in the
-// compiled program and turn it into a const.
-var hasScheduler bool
+// The compiler will insert the call to main.main() here, depending on whether
+// the scheduler is necessary.
+//
+// Without scheduler:
+//
+//     main.main()
+//
+// With scheduler:
+//
+//     coroutine := main.main(nil)
+//     scheduler(coroutine)
+func mainWrapper()
 
 // Entry point for Go. Initialize all packages and call main.main().
 //go:export main
@@ -31,18 +35,11 @@ func main() int {
 	// Enable interrupts etc.
 	postinit()
 
-	// This branch must be optimized away. Only one of the targets must remain,
-	// or there will be link errors.
-	if hasScheduler {
-		// Initialize main and run the scheduler.
-		coro := main_mainAsync(nil)
-		scheduler(coro)
-		return 0
-	} else {
-		// No scheduler is necessary. Call main directly.
-		main_main()
-		return 0
-	}
+	// Compiler-generated wrapper to main.main().
+	mainWrapper()
+
+	// For libc compatibility.
+	return 0
 }
 
 func GOMAXPROCS(n int) int {