all: use the new LLVM pass manager

The old LLVM pass manager is deprecated and should not be used anymore.
Moreover, the pass manager builder (which we used to set up a pass
pipeline) is actually removed from LLVM entirely in LLVM 17:
https://reviews.llvm.org/D145387
https://reviews.llvm.org/D145835

The new pass manager does change the binary size in many cases: both
growing and shrinking it. However, on average the binary size remains
more or less the same.

This is needed as a preparation for LLVM 17.

builder/build.go

@@ -83,8 +83,7 @@ type packageAction struct {
 	FileHashes       map[string]string // hash of every file that's part of the package
 	EmbeddedFiles    map[string]string // hash of all the //go:embed files in the package
 	Imports          map[string]string // map from imported package to action ID hash
-	OptLevel         int               // LLVM optimization level (0-3)
-	SizeLevel        int               // LLVM optimization for size level (0-2)
+	OptLevel         string            // LLVM optimization level (O0, O1, O2, Os, Oz)
 	UndefinedGlobals []string          // globals that are left as external globals (no initializer)
 }
 
@@ -158,7 +157,7 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 		return BuildResult{}, fmt.Errorf("unknown libc: %s", config.Target.Libc)
 	}
 
-	optLevel, sizeLevel, _ := config.OptLevels()
+	optLevel, speedLevel, sizeLevel := config.OptLevel()
 	compilerConfig := &compiler.Config{
 		Triple:          config.Triple(),
 		CPU:             config.CPU(),
@@ -321,7 +320,6 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 					EmbeddedFiles:    make(map[string]string, len(allFiles)),
 					Imports:          make(map[string]string, len(pkg.Pkg.Imports())),
 					OptLevel:         optLevel,
-					SizeLevel:        sizeLevel,
 					UndefinedGlobals: undefinedGlobals,
 				}
 				for filePath, hash := range pkg.FileHashes {
@@ -739,17 +737,17 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 			if config.GOOS() == "windows" {
 				// Options for the MinGW wrapper for the lld COFF linker.
 				ldflags = append(ldflags,
-					"-Xlink=/opt:lldlto="+strconv.Itoa(optLevel),
+					"-Xlink=/opt:lldlto="+strconv.Itoa(speedLevel),
 					"--thinlto-cache-dir="+filepath.Join(cacheDir, "thinlto"))
 			} else if config.GOOS() == "darwin" {
 				// Options for the ld64-compatible lld linker.
 				ldflags = append(ldflags,
-					"--lto-O"+strconv.Itoa(optLevel),
+					"--lto-O"+strconv.Itoa(speedLevel),
 					"-cache_path_lto", filepath.Join(cacheDir, "thinlto"))
 			} else {
 				// Options for the ELF linker.
 				ldflags = append(ldflags,
-					"--lto-O"+strconv.Itoa(optLevel),
+					"--lto-O"+strconv.Itoa(speedLevel),
 					"--thinlto-cache-dir="+filepath.Join(cacheDir, "thinlto"),
 				)
 			}
@@ -1062,10 +1060,9 @@ func optimizeProgram(mod llvm.Module, config *compileopts.Config) error {
 		return err
 	}
 
-	// Optimization levels here are roughly the same as Clang, but probably not
-	// exactly.
-	optLevel, sizeLevel, inlinerThreshold := config.OptLevels()
-	errs := transform.Optimize(mod, config, optLevel, sizeLevel, inlinerThreshold)
+	// Run most of the whole-program optimizations (including the whole
+	// O0/O1/O2/Os/Oz optimization pipeline).
+	errs := transform.Optimize(mod, config)
 	if len(errs) > 0 {
 		return newMultiError(errs)
 	}

compileopts/config.go

@@ -145,18 +145,18 @@ func (c *Config) Serial() string {
 
 // OptLevels returns the optimization level (0-2), size level (0-2), and inliner
 // threshold as used in the LLVM optimization pipeline.
-func (c *Config) OptLevels() (optLevel, sizeLevel int, inlinerThreshold uint) {
+func (c *Config) OptLevel() (level string, speedLevel, sizeLevel int) {
 	switch c.Options.Opt {
 	case "none", "0":
-		return 0, 0, 0 // -O0
+		return "O0", 0, 0
 	case "1":
-		return 1, 0, 0 // -O1
+		return "01", 1, 0
 	case "2":
-		return 2, 0, 225 // -O2
+		return "02", 2, 0
 	case "s":
-		return 2, 1, 225 // -Os
+		return "Os", 2, 1
 	case "z":
-		return 2, 2, 5 // -Oz, default
+		return "Oz", 2, 2 // default
 	default:
 		// This is not shown to the user: valid choices are already checked as
 		// part of Options.Verify(). It is here as a sanity check.

compiler/compiler_test.go

@@ -91,14 +91,12 @@ func TestCompiler(t *testing.T) {
 			}
 
 			// Optimize IR a little.
-			funcPasses := llvm.NewFunctionPassManagerForModule(mod)
-			defer funcPasses.Dispose()
-			funcPasses.AddInstructionCombiningPass()
-			funcPasses.InitializeFunc()
-			for fn := mod.FirstFunction(); !fn.IsNil(); fn = llvm.NextFunction(fn) {
-				funcPasses.RunFunc(fn)
+			passOptions := llvm.NewPassBuilderOptions()
+			defer passOptions.Dispose()
+			err = mod.RunPasses("instcombine", llvm.TargetMachine{}, passOptions)
+			if err != nil {
+				t.Error(err)
 			}
-			funcPasses.FinalizeFunc()
 
 			outFilePrefix := tc.file[:len(tc.file)-3]
 			if tc.target != "" {

interp/interp_test.go

@@ -79,12 +79,9 @@ func runTest(t *testing.T, pathPrefix string) {
 	}
 
 	// Run some cleanup passes to get easy-to-read outputs.
-	pm := llvm.NewPassManager()
-	defer pm.Dispose()
-	pm.AddGlobalOptimizerPass()
-	pm.AddDeadStoreEliminationPass()
-	pm.AddAggressiveDCEPass()
-	pm.Run(mod)
+	to := llvm.NewPassBuilderOptions()
+	defer to.Dispose()
+	mod.RunPasses("globalopt,dse,adce", llvm.TargetMachine{}, to)
 
 	// Read the expected output IR.
 	out, err := os.ReadFile(pathPrefix + ".out.ll")

transform/allocs_test.go

@@ -38,11 +38,12 @@ func TestAllocs2(t *testing.T) {
 	mod := compileGoFileForTesting(t, "./testdata/allocs2.go")
 
 	// Run functionattrs pass, which is necessary for escape analysis.
-	pm := llvm.NewPassManager()
-	defer pm.Dispose()
-	pm.AddInstructionCombiningPass()
-	pm.AddFunctionAttrsPass()
-	pm.Run(mod)
+	po := llvm.NewPassBuilderOptions()
+	defer po.Dispose()
+	err := mod.RunPasses("function(instcombine),function-attrs", llvm.TargetMachine{}, po)
+	if err != nil {
+		t.Error("failed to run passes:", err)
+	}
 
 	// Run heap to stack transform.
 	var testOutputs []allocsTestOutput

transform/interface-lowering_test.go

@@ -15,9 +15,11 @@ func TestInterfaceLowering(t *testing.T) {
 			t.Error(err)
 		}
 
-		pm := llvm.NewPassManager()
-		defer pm.Dispose()
-		pm.AddGlobalDCEPass()
-		pm.Run(mod)
+		po := llvm.NewPassBuilderOptions()
+		defer po.Dispose()
+		err = mod.RunPasses("globaldce", llvm.TargetMachine{}, po)
+		if err != nil {
+			t.Error("failed to run passes:", err)
+		}
 	})
 }

transform/maps_test.go

@@ -15,10 +15,11 @@ func TestOptimizeMaps(t *testing.T) {
 
 		// Run an optimization pass, to clean up the result.
 		// This shows that all code related to the map is really eliminated.
-		pm := llvm.NewPassManager()
-		defer pm.Dispose()
-		pm.AddDeadStoreEliminationPass()
-		pm.AddAggressiveDCEPass()
-		pm.Run(mod)
+		po := llvm.NewPassBuilderOptions()
+		defer po.Dispose()
+		err := mod.RunPasses("dse,adce", llvm.TargetMachine{}, po)
+		if err != nil {
+			t.Error("failed to run passes:", err)
+		}
 	})
 }

transform/optimizer.go

@@ -14,54 +14,22 @@ import (
 // OptimizePackage runs optimization passes over the LLVM module for the given
 // Go package.
 func OptimizePackage(mod llvm.Module, config *compileopts.Config) {
-	optLevel, sizeLevel, _ := config.OptLevels()
-
-	// Run function passes for each function in the module.
-	// These passes are intended to be run on each function right
-	// after they're created to reduce IR size (and maybe also for
-	// cache locality to improve performance), but for now they're
-	// run here for each function in turn. Maybe this can be
-	// improved in the future.
-	builder := llvm.NewPassManagerBuilder()
-	defer builder.Dispose()
-	builder.SetOptLevel(optLevel)
-	builder.SetSizeLevel(sizeLevel)
-	funcPasses := llvm.NewFunctionPassManagerForModule(mod)
-	defer funcPasses.Dispose()
-	builder.PopulateFunc(funcPasses)
-	funcPasses.InitializeFunc()
-	for fn := mod.FirstFunction(); !fn.IsNil(); fn = llvm.NextFunction(fn) {
-		if fn.IsDeclaration() {
-			continue
-		}
-		funcPasses.RunFunc(fn)
-	}
-	funcPasses.FinalizeFunc()
+	_, speedLevel, _ := config.OptLevel()
 
 	// Run TinyGo-specific optimization passes.
-	if optLevel > 0 {
+	if speedLevel > 0 {
 		OptimizeMaps(mod)
 	}
 }
 
 // Optimize runs a number of optimization and transformation passes over the
 // given module. Some passes are specific to TinyGo, others are generic LLVM
-// passes. You can set a preferred performance (0-3) and size (0-2) level and
-// control the limits of the inliner (higher numbers mean more inlining, set it
-// to 0 to disable entirely).
+// passes.
 //
 // Please note that some optimizations are not optional, thus Optimize must
-// alwasy be run before emitting machine code. Set all controls (optLevel,
-// sizeLevel, inlinerThreshold) to 0 to reduce the number of optimizations to a
-// minimum.
-func Optimize(mod llvm.Module, config *compileopts.Config, optLevel, sizeLevel int, inlinerThreshold uint) []error {
-	builder := llvm.NewPassManagerBuilder()
-	defer builder.Dispose()
-	builder.SetOptLevel(optLevel)
-	builder.SetSizeLevel(sizeLevel)
-	if inlinerThreshold != 0 {
-		builder.UseInlinerWithThreshold(inlinerThreshold)
-	}
+// alwasy be run before emitting machine code.
+func Optimize(mod llvm.Module, config *compileopts.Config) []error {
+	optLevel, speedLevel, _ := config.OptLevel()
 
 	// Make sure these functions are kept in tact during TinyGo transformation passes.
 	for _, name := range functionsUsedInTransforms {
@@ -84,23 +52,20 @@ func Optimize(mod llvm.Module, config *compileopts.Config, optLevel, sizeLevel i
 		}
 	}
 
-	if optLevel > 0 {
+	if speedLevel > 0 {
 		// Run some preparatory passes for the Go optimizer.
-		goPasses := llvm.NewPassManager()
-		defer goPasses.Dispose()
-		goPasses.AddGlobalDCEPass()
-		goPasses.AddGlobalOptimizerPass()
-		goPasses.AddIPSCCPPass()
-		goPasses.AddInstructionCombiningPass() // necessary for OptimizeReflectImplements
-		goPasses.AddAggressiveDCEPass()
-		goPasses.AddFunctionAttrsPass()
-		goPasses.Run(mod)
+		po := llvm.NewPassBuilderOptions()
+		defer po.Dispose()
+		err := mod.RunPasses("globaldce,globalopt,ipsccp,instcombine,adce,function-attrs", llvm.TargetMachine{}, po)
+		if err != nil {
+			return []error{fmt.Errorf("could not build pass pipeline: %w", err)}
+		}
 
 		// Run TinyGo-specific optimization passes.
 		OptimizeStringToBytes(mod)
 		OptimizeReflectImplements(mod)
 		OptimizeAllocs(mod, nil, nil)
-		err := LowerInterfaces(mod, config)
+		err = LowerInterfaces(mod, config)
 		if err != nil {
 			return []error{err}
 		}
@@ -113,7 +78,10 @@ func Optimize(mod llvm.Module, config *compileopts.Config, optLevel, sizeLevel i
 		// After interfaces are lowered, there are many more opportunities for
 		// interprocedural optimizations. To get them to work, function
 		// attributes have to be updated first.
-		goPasses.Run(mod)
+		err = mod.RunPasses("globaldce,globalopt,ipsccp,instcombine,adce,function-attrs", llvm.TargetMachine{}, po)
+		if err != nil {
+			return []error{fmt.Errorf("could not build pass pipeline: %w", err)}
+		}
 
 		// Run TinyGo-specific interprocedural optimizations.
 		OptimizeAllocs(mod, config.Options.PrintAllocs, func(pos token.Position, msg string) {
@@ -134,10 +102,12 @@ func Optimize(mod llvm.Module, config *compileopts.Config, optLevel, sizeLevel i
 		}
 
 		// Clean up some leftover symbols of the previous transformations.
-		goPasses := llvm.NewPassManager()
-		defer goPasses.Dispose()
-		goPasses.AddGlobalDCEPass()
-		goPasses.Run(mod)
+		po := llvm.NewPassBuilderOptions()
+		defer po.Dispose()
+		err = mod.RunPasses("globaldce", llvm.TargetMachine{}, po)
+		if err != nil {
+			return []error{fmt.Errorf("could not build pass pipeline: %w", err)}
+		}
 	}
 
 	if config.Scheduler() == "none" {
@@ -169,23 +139,15 @@ func Optimize(mod llvm.Module, config *compileopts.Config, optLevel, sizeLevel i
 		fn.SetLinkage(llvm.InternalLinkage)
 	}
 
-	// Run function passes again, because without it, llvm.coro.size.i32()
-	// doesn't get lowered.
-	funcPasses := llvm.NewFunctionPassManagerForModule(mod)
-	defer funcPasses.Dispose()
-	builder.PopulateFunc(funcPasses)
-	funcPasses.InitializeFunc()
-	for fn := mod.FirstFunction(); !fn.IsNil(); fn = llvm.NextFunction(fn) {
-		funcPasses.RunFunc(fn)
+	// Run the default pass pipeline.
+	// TODO: set the PrepareForThinLTO flag somehow.
+	po := llvm.NewPassBuilderOptions()
+	defer po.Dispose()
+	passes := fmt.Sprintf("default<%s>", optLevel)
+	err := mod.RunPasses(passes, llvm.TargetMachine{}, po)
+	if err != nil {
+		return []error{fmt.Errorf("could not build pass pipeline: %w", err)}
 	}
-	funcPasses.FinalizeFunc()
-
-	// Run module passes.
-	// TODO: somehow set the PrepareForThinLTO flag in the pass manager builder.
-	modPasses := llvm.NewPassManager()
-	defer modPasses.Dispose()
-	builder.Populate(modPasses)
-	modPasses.Run(mod)
 
 	hasGCPass := MakeGCStackSlots(mod)
 	if hasGCPass {

transform/transform.go

@@ -22,7 +22,7 @@ import (
 // the -opt= compiler flag.
 func AddStandardAttributes(fn llvm.Value, config *compileopts.Config) {
 	ctx := fn.Type().Context()
-	_, sizeLevel, _ := config.OptLevels()
+	_, _, sizeLevel := config.OptLevel()
 	if sizeLevel >= 1 {
 		fn.AddFunctionAttr(ctx.CreateEnumAttribute(llvm.AttributeKindID("optsize"), 0))
 	}