compiler: make panic configurable

Currently defined: abort and trap. -panic=unwind should be implemented
in the future.

compiler/compiler.go

@@ -29,18 +29,19 @@ func init() {
 
 // Configure the compiler.
 type Config struct {
-	Triple    string   // LLVM target triple, e.g. x86_64-unknown-linux-gnu (empty string means default)
-	CPU       string   // LLVM CPU name, e.g. atmega328p (empty string means default)
-	GOOS      string   //
-	GOARCH    string   //
-	GC        string   // garbage collection strategy
-	CFlags    []string // cflags to pass to cgo
-	LDFlags   []string // ldflags to pass to cgo
-	DumpSSA   bool     // dump Go SSA, for compiler debugging
-	Debug     bool     // add debug symbols for gdb
-	RootDir   string   // GOROOT for TinyGo
-	GOPATH    string   // GOPATH, like `go env GOPATH`
-	BuildTags []string // build tags for TinyGo (empty means {Config.GOOS/Config.GOARCH})
+	Triple        string   // LLVM target triple, e.g. x86_64-unknown-linux-gnu (empty string means default)
+	CPU           string   // LLVM CPU name, e.g. atmega328p (empty string means default)
+	GOOS          string   //
+	GOARCH        string   //
+	GC            string   // garbage collection strategy
+	PanicStrategy string   // panic strategy ("abort" or "trap")
+	CFlags        []string // cflags to pass to cgo
+	LDFlags       []string // ldflags to pass to cgo
+	DumpSSA       bool     // dump Go SSA, for compiler debugging
+	Debug         bool     // add debug symbols for gdb
+	RootDir       string   // GOROOT for TinyGo
+	GOPATH        string   // GOPATH, like `go env GOPATH`
+	BuildTags     []string // build tags for TinyGo (empty means {Config.GOOS/Config.GOARCH})
 }
 
 type Compiler struct {

compiler/optimizer.go

@@ -18,6 +18,10 @@ func (c *Compiler) Optimize(optLevel, sizeLevel int, inlinerThreshold uint) erro
 	}
 	builder.AddCoroutinePassesToExtensionPoints()
 
+	if c.PanicStrategy == "trap" {
+		c.replacePanicsWithTrap() // -panic=trap
+	}
+
 	// Run function passes for each function.
 	funcPasses := llvm.NewFunctionPassManagerForModule(c.mod)
 	defer funcPasses.Dispose()
@@ -113,6 +117,25 @@ func (c *Compiler) Optimize(optLevel, sizeLevel int, inlinerThreshold uint) erro
 	return nil
 }
 
+// Replace panic calls with calls to llvm.trap, to reduce code size. This is the
+// -panic=trap intrinsic.
+func (c *Compiler) replacePanicsWithTrap() {
+	trap := c.mod.NamedFunction("llvm.trap")
+	for _, name := range []string{"runtime._panic", "runtime.runtimePanic"} {
+		fn := c.mod.NamedFunction(name)
+		if fn.IsNil() {
+			continue
+		}
+		for _, use := range getUses(fn) {
+			if use.IsACallInst().IsNil() || use.CalledValue() != fn {
+				panic("expected use of a panic function to be a call")
+			}
+			c.builder.SetInsertPointBefore(use)
+			c.builder.CreateCall(trap, nil, "")
+		}
+	}
+}
+
 // Eliminate created but not used maps.
 //
 // In the future, this should statically allocate created but never modified