compiler: implement recover() built-in function

Author: aykevl

Makefile

@@ -227,6 +227,7 @@ TEST_PACKAGES_BASE = \
 	container/ring \
 	crypto/des \
 	crypto/elliptic/internal/fiat \
+	crypto/hmac \
 	crypto/internal/subtle \
 	crypto/md5 \
 	crypto/rc4 \
@@ -254,10 +255,12 @@ TEST_PACKAGES_BASE = \
 	os \
 	path \
 	reflect \
+	strconv \
 	sync \
 	testing \
 	testing/iotest \
 	text/scanner \
+	text/template/parse \
 	unicode \
 	unicode/utf16 \
 	unicode/utf8 \

compileopts/target.go

@@ -319,7 +319,7 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 			// systems so we need separate assembly files.
 			suffix = "_windows"
 		}
-		spec.ExtraFiles = append(spec.ExtraFiles, "src/runtime/gc_"+goarch+suffix+".S")
+		spec.ExtraFiles = append(spec.ExtraFiles, "src/runtime/asm_"+goarch+suffix+".S")
 		spec.ExtraFiles = append(spec.ExtraFiles, "src/internal/task/task_stack_"+goarch+suffix+".S")
 	}
 	if goarch != runtime.GOARCH {

compiler/calls.go

@@ -33,17 +33,36 @@ const (
 	paramIsDeferenceableOrNull = 1 << iota
 )
 
-// createCall creates a new call to runtime.<fnName> with the given arguments.
-func (b *builder) createRuntimeCall(fnName string, args []llvm.Value, name string) llvm.Value {
+// createRuntimeCallCommon creates a runtime call. Use createRuntimeCall or
+// createRuntimeInvoke instead.
+func (b *builder) createRuntimeCallCommon(fnName string, args []llvm.Value, name string, isInvoke bool) llvm.Value {
 	fn := b.program.ImportedPackage("runtime").Members[fnName].(*ssa.Function)
 	llvmFn := b.getFunction(fn)
 	if llvmFn.IsNil() {
 		panic("trying to call non-existent function: " + fn.RelString(nil))
 	}
 	args = append(args, llvm.Undef(b.i8ptrType)) // unused context parameter
+	if isInvoke {
+		return b.createInvoke(llvmFn, args, name)
+	}
 	return b.createCall(llvmFn, args, name)
 }
 
+// createRuntimeCall creates a new call to runtime.<fnName> with the given
+// arguments.
+func (b *builder) createRuntimeCall(fnName string, args []llvm.Value, name string) llvm.Value {
+	return b.createRuntimeCallCommon(fnName, args, name, false)
+}
+
+// createRuntimeInvoke creates a new call to runtime.<fnName> with the given
+// arguments. If the runtime call panics, control flow is diverted to the
+// landing pad block.
+// Note that "invoke" here is meant in the LLVM sense (a call that can
+// panic/throw), not in the Go sense (an interface method call).
+func (b *builder) createRuntimeInvoke(fnName string, args []llvm.Value, name string) llvm.Value {
+	return b.createRuntimeCallCommon(fnName, args, name, true)
+}
+
 // createCall creates a call to the given function with the arguments possibly
 // expanded.
 func (b *builder) createCall(fn llvm.Value, args []llvm.Value, name string) llvm.Value {
@@ -55,6 +74,15 @@ func (b *builder) createCall(fn llvm.Value, args []llvm.Value, name string) llvm
 	return b.CreateCall(fn, expanded, name)
 }
 
+// createInvoke is like createCall but continues execution at the landing pad if
+// the call resulted in a panic.
+func (b *builder) createInvoke(fn llvm.Value, args []llvm.Value, name string) llvm.Value {
+	if b.hasDeferFrame() {
+		b.createInvokeCheckpoint()
+	}
+	return b.createCall(fn, args, name)
+}
+
 // Expand an argument type to a list that can be used in a function call
 // parameter list.
 func (c *compilerContext) expandFormalParamType(t llvm.Type, name string, goType types.Type) []paramInfo {

compiler/compiler.go

@@ -137,6 +137,8 @@ type builder struct {
 	currentBlock      *ssa.BasicBlock
 	phis              []phiNode
 	deferPtr          llvm.Value
+	deferFrame        llvm.Value
+	landingpad        llvm.BasicBlock
 	difunc            llvm.Metadata
 	dilocals          map[*types.Var]llvm.Metadata
 	initInlinedAt     llvm.Metadata            // fake inlinedAt position
@@ -1038,6 +1040,12 @@ func (b *builder) createFunction() {
 		}
 	}
 
+	if b.hasDeferFrame() {
+		// Create the landing pad block, where execution continues after a
+		// panic.
+		b.createLandingPad()
+	}
+
 	// Resolve phi nodes
 	for _, phi := range b.phis {
 		block := phi.ssa.Block()
@@ -1165,9 +1173,12 @@ func (b *builder) createInstruction(instr ssa.Instruction) {
 		b.createMapUpdate(mapType.Key(), m, key, value, instr.Pos())
 	case *ssa.Panic:
 		value := b.getValue(instr.X)
-		b.createRuntimeCall("_panic", []llvm.Value{value}, "")
+		b.createRuntimeInvoke("_panic", []llvm.Value{value}, "")
 		b.CreateUnreachable()
 	case *ssa.Return:
+		if b.hasDeferFrame() {
+			b.createRuntimeCall("destroyDeferFrame", []llvm.Value{b.deferFrame}, "")
+		}
 		if len(instr.Results) == 0 {
 			b.CreateRetVoid()
 		} else if len(instr.Results) == 1 {
@@ -1356,7 +1367,13 @@ func (b *builder) createBuiltin(argTypes []types.Type, argValues []llvm.Value, c
 		cplx := argValues[0]
 		return b.CreateExtractValue(cplx, 0, "real"), nil
 	case "recover":
-		return b.createRuntimeCall("_recover", nil, ""), nil
+		useParentFrame := uint64(0)
+		if b.hasDeferFrame() {
+			// recover() should return the panic value of the parent function,
+			// not of the current function.
+			useParentFrame = 1
+		}
+		return b.createRuntimeCall("_recover", []llvm.Value{llvm.ConstInt(b.ctx.Int1Type(), useParentFrame, false)}, ""), nil
 	case "ssa:wrapnilchk":
 		// TODO: do an actual nil check?
 		return argValues[0], nil
@@ -1443,6 +1460,12 @@ func (b *builder) createFunctionCall(instr *ssa.CallCommon) (llvm.Value, error)
 			return b.createVolatileLoad(instr)
 		case strings.HasPrefix(name, "runtime/volatile.Store"):
 			return b.createVolatileStore(instr)
+		case name == "runtime.supportsRecover":
+			supportsRecover := uint64(0)
+			if b.supportsRecover() {
+				supportsRecover = 1
+			}
+			return llvm.ConstInt(b.ctx.Int1Type(), supportsRecover, false), nil
 		case strings.HasPrefix(name, "sync/atomic."):
 			val, ok := b.createAtomicOp(instr)
 			if ok {
@@ -1505,7 +1528,7 @@ func (b *builder) createFunctionCall(instr *ssa.CallCommon) (llvm.Value, error)
 		params = append(params, context)
 	}
 
-	return b.createCall(callee, params, ""), nil
+	return b.createInvoke(callee, params, ""), nil
 }
 
 // getValue returns the LLVM value of a constant, function value, global, or

compiler/compiler_test.go

@@ -101,6 +101,7 @@ func TestCompiler(t *testing.T) {
 			}
 			compilerConfig := &Config{
 				Triple:             config.Triple(),
+				Features:           config.Features(),
 				GOOS:               config.GOOS(),
 				GOARCH:             config.GOARCH(),
 				CodeModel:          config.CodeModel(),