cmd/compile/internal/devirtualize: improve concrete type analysis

This change improves the concrete type analysis in the devirtualizer,
it not longer relies on ir.Reassigned, it now statically tries to
determine the concrete type of an interface, even when assigned
multiple times, following type assertions and iface conversions.

Alternative to CL 649195

Updates golang#69521
Fixes golang#64824

Change-Id: Ib1656e19f3619ab2e1e6b2c78346cc320490b2af
GitHub-Last-Rev: e8fa0b1
GitHub-Pull-Request: golang#71935
Reviewed-on: https://go-review.googlesource.com/c/go/+/652036
Reviewed-by: Michael Pratt <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Keith Randall <[email protected]>

Author: mateusz834

src/cmd/compile/internal/devirtualize/devirtualize.go

@@ -45,6 +45,8 @@ func DevirtualizeAndInlinePackage(pkg *ir.Package, profile *pgoir.Profile) {
 	inlState := make(map[*ir.Func]*inlClosureState)
 	calleeUseCounts := make(map[*ir.Func]int)
 
+	var state devirtualize.State
+
 	// Pre-process all the functions, adding parentheses around call sites and starting their "inl state".
 	for _, fn := range typecheck.Target.Funcs {
 		bigCaller := base.Flag.LowerL != 0 && inline.IsBigFunc(fn)
@@ -58,7 +60,7 @@ func DevirtualizeAndInlinePackage(pkg *ir.Package, profile *pgoir.Profile) {
 
 		// Do a first pass at counting call sites.
 		for i := range s.parens {
-			s.resolve(i)
+			s.resolve(&state, i)
 		}
 	}
 
@@ -102,10 +104,11 @@ func DevirtualizeAndInlinePackage(pkg *ir.Package, profile *pgoir.Profile) {
 					for {
 						for i := l0; i < l1; i++ { // can't use "range parens" here
 							paren := s.parens[i]
-							if new := s.edit(i); new != nil {
+							if origCall, inlinedCall := s.edit(&state, i); inlinedCall != nil {
 								// Update AST and recursively mark nodes.
-								paren.X = new
-								ir.EditChildren(new, s.mark) // mark may append to parens
+								paren.X = inlinedCall
+								ir.EditChildren(inlinedCall, s.mark) // mark may append to parens
+								state.InlinedCall(s.fn, origCall, inlinedCall)
 								done = false
 							}
 						}
@@ -114,7 +117,7 @@ func DevirtualizeAndInlinePackage(pkg *ir.Package, profile *pgoir.Profile) {
 							break
 						}
 						for i := l0; i < l1; i++ {
-							s.resolve(i)
+							s.resolve(&state, i)
 						}
 
 					}
@@ -188,7 +191,7 @@ type inlClosureState struct {
 // resolve attempts to resolve a call to a potentially inlineable callee
 // and updates use counts on the callees.  Returns the call site count
 // for that callee.
-func (s *inlClosureState) resolve(i int) (*ir.Func, int) {
+func (s *inlClosureState) resolve(state *devirtualize.State, i int) (*ir.Func, int) {
 	p := s.parens[i]
 	if i < len(s.resolved) {
 		if callee := s.resolved[i]; callee != nil {
@@ -200,7 +203,7 @@ func (s *inlClosureState) resolve(i int) (*ir.Func, int) {
 	if !ok { // previously inlined
 		return nil, -1
 	}
-	devirtualize.StaticCall(call)
+	devirtualize.StaticCall(state, call)
 	if callee := inline.InlineCallTarget(s.fn, call, s.profile); callee != nil {
 		for len(s.resolved) <= i {
 			s.resolved = append(s.resolved, nil)
@@ -213,23 +216,23 @@ func (s *inlClosureState) resolve(i int) (*ir.Func, int) {
 	return nil, 0
 }
 
-func (s *inlClosureState) edit(i int) ir.Node {
+func (s *inlClosureState) edit(state *devirtualize.State, i int) (*ir.CallExpr, *ir.InlinedCallExpr) {
 	n := s.parens[i].X
 	call, ok := n.(*ir.CallExpr)
 	if !ok {
-		return nil
+		return nil, nil
 	}
 	// This is redundant with earlier calls to
 	// resolve, but because things can change it
 	// must be re-checked.
-	callee, count := s.resolve(i)
+	callee, count := s.resolve(state, i)
 	if count <= 0 {
-		return nil
+		return nil, nil
 	}
 	if inlCall := inline.TryInlineCall(s.fn, call, s.bigCaller, s.profile, count == 1 && callee.ClosureParent != nil); inlCall != nil {
-		return inlCall
+		return call, inlCall
 	}
-	return nil
+	return nil, nil
 }
 
 // Mark inserts parentheses, and is called repeatedly.
@@ -338,16 +341,18 @@ func (s *inlClosureState) unparenthesize() {
 // returns.
 func (s *inlClosureState) fixpoint() bool {
 	changed := false
+	var state devirtualize.State
 	ir.WithFunc(s.fn, func() {
 		done := false
 		for !done {
 			done = true
 			for i := 0; i < len(s.parens); i++ { // can't use "range parens" here
 				paren := s.parens[i]
-				if new := s.edit(i); new != nil {
+				if origCall, inlinedCall := s.edit(&state, i); inlinedCall != nil {
 					// Update AST and recursively mark nodes.
-					paren.X = new
-					ir.EditChildren(new, s.mark) // mark may append to parens
+					paren.X = inlinedCall
+					ir.EditChildren(inlinedCall, s.mark) // mark may append to parens
+					state.InlinedCall(s.fn, origCall, inlinedCall)
 					done = false
 					changed = true
 				}

src/cmd/compile/internal/inline/interleaved/interleaved.go

@@ -677,6 +677,11 @@ type TypeAssertExpr struct {
 
 	// An internal/abi.TypeAssert descriptor to pass to the runtime.
 	Descriptor *obj.LSym
+
+	// When set to true, if this assert would panic, then use a nil pointer panic
+	// instead of an interface conversion panic.
+	// It must not be set for type asserts using the commaok form.
+	UseNilPanic bool
 }
 
 func NewTypeAssertExpr(pos src.XPos, x Node, typ *types.Type) *TypeAssertExpr {

src/cmd/compile/internal/ir/expr.go

@@ -2961,6 +2961,7 @@ func (r *reader) multiExpr() []ir.Node {
 		as.Def = true
 		for i := range results {
 			tmp := r.temp(pos, r.typ())
+			tmp.Defn = as
 			as.PtrInit().Append(ir.NewDecl(pos, ir.ODCL, tmp))
 			as.Lhs.Append(tmp)
 

src/cmd/compile/internal/noder/reader.go

@@ -5827,6 +5827,25 @@ func (s *state) dottype(n *ir.TypeAssertExpr, commaok bool) (res, resok *ssa.Val
 	if n.ITab != nil {
 		targetItab = s.expr(n.ITab)
 	}
+
+	if n.UseNilPanic {
+		if commaok {
+			base.Fatalf("unexpected *ir.TypeAssertExpr with UseNilPanic == true && commaok == true")
+		}
+		if n.Type().IsInterface() {
+			// Currently we do not expect the compiler to emit type asserts with UseNilPanic, that assert to an interface type.
+			// If needed, this can be relaxed in the future, but for now we can assert that.
+			base.Fatalf("unexpected *ir.TypeAssertExpr with UseNilPanic == true && Type().IsInterface() == true")
+		}
+		typs := s.f.Config.Types
+		iface = s.newValue2(
+			ssa.OpIMake,
+			iface.Type,
+			s.nilCheck(s.newValue1(ssa.OpITab, typs.BytePtr, iface)),
+			s.newValue1(ssa.OpIData, typs.BytePtr, iface),
+		)
+	}
+
 	return s.dottype1(n.Pos(), n.X.Type(), n.Type(), iface, nil, target, targetItab, commaok, n.Descriptor)
 }
 

src/cmd/compile/internal/ssagen/ssa.go

@@ -471,3 +471,17 @@ func BenchmarkHash256K(b *testing.B) {
 func BenchmarkHash1M(b *testing.B) {
 	benchmarkSize(b, 1024*1024)
 }
+
+func TestAllocatonsWithTypeAsserts(t *testing.T) {
+	cryptotest.SkipTestAllocations(t)
+	allocs := testing.AllocsPerRun(100, func() {
+		h := New()
+		h.Write([]byte{1, 2, 3})
+		marshaled, _ := h.(encoding.BinaryMarshaler).MarshalBinary()
+		marshaled, _ = h.(encoding.BinaryAppender).AppendBinary(marshaled[:0])
+		h.(encoding.BinaryUnmarshaler).UnmarshalBinary(marshaled)
+	})
+	if allocs != 0 {
+		t.Fatalf("allocs = %v; want = 0", allocs)
+	}
+}

src/crypto/sha256/sha256_test.go

@@ -344,6 +344,11 @@ func (h inlineWrapper) dump(pcs []uintptr) {
 
 func inlinedWrapperCallerDump(pcs []uintptr) {
 	var h inlineWrapperInterface
+
+	// Take the address of h, such that h.dump() call (below)
+	// does not get devirtualized by the compiler.
+	_ = &h
+
 	h = &inlineWrapper{}
 	h.dump(pcs)
 }