cmd/compile/internal/inline/inlheur: rescore callsites based on result use

Add a post-processing pass that updates the scores on callsites based
on how their results are used. This is similar to the "param feeds
unmodified into <XXX>" heuristics, but applies to returned results
instead: if we know that function F always returns a constant, and we
can see that the result from a given call feeds unmodified into an
if/switch, then decrease the score on the call to encourage inlining.

Change-Id: If513765c79d868cbdf672facbff9d92ad24f909e
Reviewed-on: https://go-review.googlesource.com/c/go/+/521819
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/compile/internal/inline/inlheur/analyze.go

@@ -222,11 +222,6 @@ func emitDumpToFile(dumpfile string) {
 // "-d=dumpinlfuncprops=..." command line flag, intended for use
 // primarily in unit testing.
 func captureFuncDumpEntry(fn *ir.Func, canInline func(*ir.Func)) {
-	if debugTrace&debugTraceFuncs != 0 {
-		fmt.Fprintf(os.Stderr, "=-= capturing dump for %v:\n",
-			fn.Sym().Name)
-	}
-
 	// avoid capturing compiler-generated equality funcs.
 	if strings.HasPrefix(fn.Sym().Name, ".eq.") {
 		return
@@ -249,6 +244,9 @@ func captureFuncDumpEntry(fn *ir.Func, canInline func(*ir.Func)) {
 		// so don't add them more than once.
 		return
 	}
+	if debugTrace&debugTraceFuncs != 0 {
+		fmt.Fprintf(os.Stderr, "=-= capturing dump for %v:\n", fn)
+	}
 	dumpBuffer[fn] = fih
 }
 

src/cmd/compile/internal/inline/inlheur/analyze_func_callsites.go

@@ -182,6 +182,8 @@ func ScoreCalls(fn *ir.Func) {
 		return
 	}
 
+	resultNameTab := make(map[*ir.Name]resultPropAndCS)
+
 	// Sort callsites to avoid any surprises with non deterministic
 	// map iteration order (this is probably not needed, but here just
 	// in case).
@@ -214,10 +216,14 @@ func ScoreCalls(fn *ir.Func) {
 		}
 		cs.Score, cs.ScoreMask = computeCallSiteScore(cs.Callee, cprops, cs.Call, cs.Flags)
 
+		examineCallResults(cs, resultNameTab)
+
 		if debugTrace&debugTraceScoring != 0 {
 			fmt.Fprintf(os.Stderr, "=-= scoring call at %s: flags=%d score=%d fih=%v deser=%v\n", fmtFullPos(cs.Call.Pos()), cs.Flags, cs.Score, fihcprops, desercprops)
 		}
 	}
+
+	rescoreBasedOnCallResultUses(fn, resultNameTab, fih.cstab)
 }
 
 func (csa *callSiteAnalyzer) nodeVisitPre(n ir.Node) {
@@ -290,12 +296,12 @@ func hasTopLevelLoopBodyReturnOrBreak(loopBody ir.Nodes) bool {
 //
 // Here the top-level assignment statement for the foo() call is the
 // statement assigning to "x"; the top-level assignment for "bar()"
-// call is the assignment to x,y.   For the baz() and blah() calls,
+// call is the assignment to x,y. For the baz() and blah() calls,
 // there is no top level assignment statement.
 //
-// The unstated goal here is that we want to use the containing assignment
-// to establish a connection between a given call and the variables
-// to which its results/returns are being assigned.
+// The unstated goal here is that we want to use the containing
+// assignment to establish a connection between a given call and the
+// variables to which its results/returns are being assigned.
 //
 // Note that for the "bar" command above, the front end sometimes
 // decomposes this into two assignments, the first one assigning the

src/cmd/compile/internal/inline/inlheur/funcprops_test.go

@@ -37,7 +37,7 @@ func TestFuncProperties(t *testing.T) {
 	// scheme.
 
 	testcases := []string{"funcflags", "returns", "params",
-		"acrosscall", "calls"}
+		"acrosscall", "calls", "returns2"}
 	for _, tc := range testcases {
 		dumpfile, err := gatherPropsDumpForFile(t, tc, td)
 		if err != nil {

src/cmd/compile/internal/inline/inlheur/score_callresult_uses.go

@@ -0,0 +1,423 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package inlheur
+
+import (
+	"cmd/compile/internal/ir"
+	"fmt"
+	"os"
+)
+
+// This file contains code to re-score callsites based on how the
+// results of the call were used.  Example:
+//
+//    func foo() {
+//       x, fptr := bar()
+//       switch x {
+//         case 10: fptr = baz()
+//         default: blix()
+//       }
+//       fptr(100)
+//     }
+//
+// The initial scoring pass will assign a score to "bar()" based on
+// various criteria, however once the first pass of scoring is done,
+// we look at the flags on the result from bar, and check to see
+// how those results are used. If bar() always returns the same constant
+// for its first result, and if the variable receiving that result
+// isn't redefined, and if that variable feeds into an if/switch
+// condition, then we will try to adjust the score for "bar" (on the
+// theory that if we inlined, we can constant fold / deadcode).
+
+type resultPropAndCS struct {
+	defcs *CallSite
+	props ResultPropBits
+}
+
+type resultUseAnalyzer struct {
+	resultNameTab map[*ir.Name]resultPropAndCS
+	fn            *ir.Func
+	cstab         CallSiteTab
+	*condLevelTracker
+}
+
+// rescoreBasedOnCallResultUses examines how call results are used,
+// and tries to update the scores of calls based on how their results
+// are used in the function.
+func rescoreBasedOnCallResultUses(fn *ir.Func, resultNameTab map[*ir.Name]resultPropAndCS, cstab CallSiteTab) {
+	if os.Getenv("THANM_DEBUG") != "" {
+		return
+	}
+	enableDebugTraceIfEnv()
+	rua := &resultUseAnalyzer{
+		resultNameTab:    resultNameTab,
+		fn:               fn,
+		cstab:            cstab,
+		condLevelTracker: new(condLevelTracker),
+	}
+	var doNode func(ir.Node) bool
+	doNode = func(n ir.Node) bool {
+		rua.nodeVisitPre(n)
+		ir.DoChildren(n, doNode)
+		rua.nodeVisitPost(n)
+		return false
+	}
+	doNode(fn)
+	disableDebugTrace()
+}
+
+func examineCallResults(cs *CallSite, resultNameTab map[*ir.Name]resultPropAndCS) {
+	if debugTrace&debugTraceScoring != 0 {
+		fmt.Fprintf(os.Stderr, "=-= examining call results for %q\n",
+			EncodeCallSiteKey(cs))
+	}
+
+	// Invoke a helper to pick out the specific ir.Name's the results
+	// from this call are assigned into, e.g. "x, y := fooBar()". If
+	// the call is not part of an assignment statement, or if the
+	// variables in question are not newly defined, then we'll receive
+	// an empty list here.
+	//
+	names, autoTemps, props := namesDefined(cs)
+	if len(names) == 0 {
+		return
+	}
+
+	if debugTrace&debugTraceScoring != 0 {
+		fmt.Fprintf(os.Stderr, "=-= %d names defined\n", len(names))
+	}
+
+	// For each returned value, if the value has interesting
+	// properties (ex: always returns the same constant), and the name
+	// in question is never redefined, then make an entry in the
+	// result table for it.
+	const interesting = (ResultIsConcreteTypeConvertedToInterface |
+		ResultAlwaysSameConstant | ResultAlwaysSameInlinableFunc | ResultAlwaysSameFunc)
+	for idx, n := range names {
+		rprop := props.ResultFlags[idx]
+
+		if debugTrace&debugTraceScoring != 0 {
+			fmt.Fprintf(os.Stderr, "=-= props for ret %d %q: %s\n",
+				idx, n.Sym().Name, rprop.String())
+		}
+
+		if rprop&interesting == 0 {
+			continue
+		}
+		if ir.Reassigned(n) {
+			continue
+		}
+		if _, ok := resultNameTab[n]; ok {
+			panic("should never happen")
+		}
+		entry := resultPropAndCS{
+			defcs: cs,
+			props: rprop,
+		}
+		resultNameTab[n] = entry
+		if autoTemps[idx] != nil {
+			resultNameTab[autoTemps[idx]] = entry
+		}
+		if debugTrace&debugTraceScoring != 0 {
+			fmt.Fprintf(os.Stderr, "=-= add resultNameTab table entry n=%v autotemp=%v props=%s\n", n, autoTemps[idx], rprop.String())
+		}
+	}
+}
+
+// namesDefined returns a list of ir.Name's corresponding to locals
+// that receive the results from the call at site 'cs', plus the
+// properties object for the called function. If a given result
+// isn't cleanly assigned to a newly defined local, the
+// slot for that result in the returned list will be nil. Example:
+//
+//	call                             returned name list
+//
+//	x := foo()                       [ x ]
+//	z, y := bar()                    [ nil, nil ]
+//	_, q := baz()                    [ nil, q ]
+//
+// In the case of a multi-return call, such as "x, y := foo()",
+// the pattern we see from the front end will be a call op
+// assigning to auto-temps, and then an assignment of the auto-temps
+// to the user-level variables. In such cases we return
+// first the user-level variable (in the first func result)
+// and then the auto-temp name in the second result.
+func namesDefined(cs *CallSite) ([]*ir.Name, []*ir.Name, *FuncProps) {
+	// If this call doesn't feed into an assignment (and of course not
+	// all calls do), then we don't have anything to work with here.
+	if cs.Assign == nil {
+		return nil, nil, nil
+	}
+	fih, ok := fpmap[cs.Callee]
+	if !ok {
+		// TODO: add an assert/panic here.
+		return nil, nil, nil
+	}
+	if len(fih.props.ResultFlags) == 0 {
+		return nil, nil, nil
+	}
+
+	// Single return case.
+	if len(fih.props.ResultFlags) == 1 {
+		asgn, ok := cs.Assign.(*ir.AssignStmt)
+		if !ok {
+			return nil, nil, nil
+		}
+		// locate name being assigned
+		aname, ok := asgn.X.(*ir.Name)
+		if !ok {
+			return nil, nil, nil
+		}
+		return []*ir.Name{aname}, []*ir.Name{nil}, fih.props
+	}
+
+	// Multi-return case
+	asgn, ok := cs.Assign.(*ir.AssignListStmt)
+	if !ok || !asgn.Def {
+		return nil, nil, nil
+	}
+	userVars := make([]*ir.Name, len(fih.props.ResultFlags))
+	autoTemps := make([]*ir.Name, len(fih.props.ResultFlags))
+	for idx, x := range asgn.Lhs {
+		if n, ok := x.(*ir.Name); ok {
+			userVars[idx] = n
+			r := asgn.Rhs[idx]
+			if r.Op() == ir.OCONVNOP {
+				r = r.(*ir.ConvExpr).X
+			}
+			if ir.IsAutoTmp(r) {
+				autoTemps[idx] = r.(*ir.Name)
+			}
+			if debugTrace&debugTraceScoring != 0 {
+				fmt.Fprintf(os.Stderr, "=-= multi-ret namedef uv=%v at=%v\n",
+					x, autoTemps[idx])
+			}
+		} else {
+			return nil, nil, nil
+		}
+	}
+	return userVars, autoTemps, fih.props
+}
+
+func (rua *resultUseAnalyzer) nodeVisitPost(n ir.Node) {
+	rua.condLevelTracker.post(n)
+}
+
+func (rua *resultUseAnalyzer) nodeVisitPre(n ir.Node) {
+	rua.condLevelTracker.pre(n)
+	switch n.Op() {
+	case ir.OCALLINTER:
+		if debugTrace&debugTraceScoring != 0 {
+			fmt.Fprintf(os.Stderr, "=-= rescore examine iface call %v:\n", n)
+		}
+		rua.callTargetCheckResults(n)
+	case ir.OCALLFUNC:
+		if debugTrace&debugTraceScoring != 0 {
+			fmt.Fprintf(os.Stderr, "=-= rescore examine call %v:\n", n)
+		}
+		rua.callTargetCheckResults(n)
+	case ir.OIF:
+		ifst := n.(*ir.IfStmt)
+		rua.foldCheckResults(ifst.Cond)
+	case ir.OSWITCH:
+		swst := n.(*ir.SwitchStmt)
+		if swst.Tag != nil {
+			rua.foldCheckResults(swst.Tag)
+		}
+
+	}
+}
+
+// callTargetCheckResults examines a given call to see whether the
+// callee expression is potentially an inlinable function returned
+// from a potentially inlinable call. Examples:
+//
+//	Scenario 1: named intermediate
+//
+//	   fn1 := foo()         conc := bar()
+//	   fn1("blah")          conc.MyMethod()
+//
+//	Scenario 2: returned func or concrete object feeds directly to call
+//
+//	   foo()("blah")        bar().MyMethod()
+//
+// In the second case although at the source level the result of the
+// direct call feeds right into the method call or indirect call,
+// we're relying on the front end having inserted an auto-temp to
+// capture the value.
+func (rua *resultUseAnalyzer) callTargetCheckResults(call ir.Node) {
+	ce := call.(*ir.CallExpr)
+	rname := rua.getCallResultName(ce)
+	if rname == nil {
+		return
+	}
+	if debugTrace&debugTraceScoring != 0 {
+		fmt.Fprintf(os.Stderr, "=-= staticvalue returns %v:\n",
+			rname)
+	}
+	if rname.Class != ir.PAUTO {
+		return
+	}
+	switch call.Op() {
+	case ir.OCALLINTER:
+		if debugTrace&debugTraceScoring != 0 {
+			fmt.Fprintf(os.Stderr, "=-= in %s checking %v for cci prop:\n",
+				rua.fn.Sym().Name, rname)
+		}
+		if cs := rua.returnHasProp(rname, ResultIsConcreteTypeConvertedToInterface); cs != nil {
+			// FIXME: add cond level support here
+			adj := passConcreteToItfCallAdj
+			cs.Score, cs.ScoreMask = adjustScore(adj, cs.Score, cs.ScoreMask)
+			adj = callResultRescoreAdj
+			cs.Score, cs.ScoreMask = adjustScore(adj, cs.Score, cs.ScoreMask)
+		}
+	case ir.OCALLFUNC:
+		if debugTrace&debugTraceScoring != 0 {
+			fmt.Fprintf(os.Stderr, "=-= in %s checking %v for samefunc props:\n",
+				rua.fn.Sym().Name, rname)
+			v, ok := rua.resultNameTab[rname]
+			if !ok {
+				fmt.Fprintf(os.Stderr, "=-= no entry for %v in rt\n", rname)
+			} else {
+				fmt.Fprintf(os.Stderr, "=-= props for %v: %q\n", rname, v.props.String())
+			}
+		}
+		if cs := rua.returnHasProp(rname, ResultAlwaysSameInlinableFunc); cs != nil {
+			// FIXME: add cond level support here
+			adj := passInlinableFuncToIndCallAdj
+			cs.Score, cs.ScoreMask = adjustScore(adj, cs.Score, cs.ScoreMask)
+			adj = callResultRescoreAdj
+			cs.Score, cs.ScoreMask = adjustScore(adj, cs.Score, cs.ScoreMask)
+		} else if cs := rua.returnHasProp(rname, ResultAlwaysSameFunc); cs != nil {
+			// FIXME: add cond level support here
+			adj := passFuncToIndCallAdj
+			cs.Score, cs.ScoreMask = adjustScore(adj, cs.Score, cs.ScoreMask)
+			adj = callResultRescoreAdj
+			cs.Score, cs.ScoreMask = adjustScore(adj, cs.Score, cs.ScoreMask)
+		}
+	}
+}
+
+// foldCheckResults examines the specified if/switch condition 'cond'
+// to see if it refers to locals defined by a (potentially inlinable)
+// function call at call site C, and if so, whether 'cond' contains
+// only combinations of simple references to all of the names in
+// 'names' with selected constants + operators. If these criteria are
+// met, then we adjust the score for call site C to reflect the
+// fact that inlining will enable deadcode and/or constant propagation.
+// Note: for this heuristic to kick in, the names in question have to
+// be all from the same callsite. Examples:
+//
+//	  q, r := baz()	    x, y := foo()
+//	  switch q+r {		a, b, c := bar()
+//		...			    if x && y && a && b && c {
+//	  }					   ...
+//					    }
+//
+// For the call to "baz" above we apply a score adjustment, but not
+// for the calls to "foo" or "bar".
+func (rua *resultUseAnalyzer) foldCheckResults(cond ir.Node) {
+	namesUsed := collectNamesUsed(cond)
+	if len(namesUsed) == 0 {
+		return
+	}
+	var cs *CallSite
+	for _, n := range namesUsed {
+		rpcs, found := rua.resultNameTab[n]
+		if !found {
+			return
+		}
+		if cs != nil && rpcs.defcs != cs {
+			return
+		}
+		cs = rpcs.defcs
+		if rpcs.props&ResultAlwaysSameConstant == 0 {
+			return
+		}
+	}
+	if debugTrace&debugTraceScoring != 0 {
+		nls := func(nl []*ir.Name) string {
+			r := ""
+			for _, n := range nl {
+				r += " " + n.Sym().Name
+			}
+			return r
+		}
+		fmt.Fprintf(os.Stderr, "=-= calling ShouldFoldIfNameConstant on names={%s} cond=%v\n", nls(namesUsed), cond)
+	}
+
+	if !ShouldFoldIfNameConstant(cond, namesUsed) {
+		return
+	}
+	// FIXME: add cond level support here
+	adj := passConstToIfAdj
+	cs.Score, cs.ScoreMask = adjustScore(adj, cs.Score, cs.ScoreMask)
+	adj = callResultRescoreAdj
+	cs.Score, cs.ScoreMask = adjustScore(adj, cs.Score, cs.ScoreMask)
+}
+
+func collectNamesUsed(expr ir.Node) []*ir.Name {
+	res := []*ir.Name{}
+	ir.Visit(expr, func(n ir.Node) {
+		if n.Op() != ir.ONAME {
+			return
+		}
+		nn := n.(*ir.Name)
+		if nn.Class != ir.PAUTO {
+			return
+		}
+		res = append(res, nn)
+	})
+	return res
+}
+
+func (rua *resultUseAnalyzer) returnHasProp(name *ir.Name, prop ResultPropBits) *CallSite {
+	v, ok := rua.resultNameTab[name]
+	if !ok {
+		return nil
+	}
+	if v.props&prop == 0 {
+		return nil
+	}
+	return v.defcs
+}
+
+func (rua *resultUseAnalyzer) getCallResultName(ce *ir.CallExpr) *ir.Name {
+	var callTarg ir.Node
+	if sel, ok := ce.X.(*ir.SelectorExpr); ok {
+		// method call
+		callTarg = sel.X
+	} else if ctarg, ok := ce.X.(*ir.Name); ok {
+		// regular call
+		callTarg = ctarg
+	} else {
+		return nil
+	}
+	r := ir.StaticValue(callTarg)
+	if debugTrace&debugTraceScoring != 0 {
+		fmt.Fprintf(os.Stderr, "=-= staticname on %v returns %v:\n",
+			callTarg, r)
+	}
+	if r.Op() == ir.OCALLFUNC {
+		// This corresponds to the "x := foo()" case; here
+		// ir.StaticValue has brought us all the way back to
+		// the call expression itself. We need to back off to
+		// the name defined by the call; do this by looking up
+		// the callsite.
+		ce := r.(*ir.CallExpr)
+		cs, ok := rua.cstab[ce]
+		if !ok {
+			return nil
+		}
+		names, _, _ := namesDefined(cs)
+		if len(names) == 0 {
+			return nil
+		}
+		return names[0]
+	} else if r.Op() == ir.ONAME {
+		return r.(*ir.Name)
+	}
+	return nil
+}

src/cmd/compile/internal/inline/inlheur/scoreadjusttyp_string.go

@@ -20,7 +20,8 @@ func _() {
 	_ = x[passFuncToNestedIndCallAdj-256]
 	_ = x[passInlinableFuncToIndCallAdj-512]
 	_ = x[passInlinableFuncToNestedIndCallAdj-1024]
-	_ = x[lastAdj-1024]
+	_ = x[callResultRescoreAdj-2048]
+	_ = x[lastAdj-2048]
 }
 
 var _scoreAdjustTyp_value = [...]uint64{
@@ -35,12 +36,13 @@ var _scoreAdjustTyp_value = [...]uint64{
 	0x100, /* passFuncToNestedIndCallAdj */
 	0x200, /* passInlinableFuncToIndCallAdj */
 	0x400, /* passInlinableFuncToNestedIndCallAdj */
-	0x400, /* lastAdj */
+	0x800, /* callResultRescoreAdj */
+	0x800, /* lastAdj */
 }
 
-const _scoreAdjustTyp_name = "panicPathAdjinitFuncAdjinLoopAdjpassConstToIfAdjpassConstToNestedIfAdjpassConcreteToItfCallAdjpassConcreteToNestedItfCallAdjpassFuncToIndCallAdjpassFuncToNestedIndCallAdjpassInlinableFuncToIndCallAdjpassInlinableFuncToNestedIndCallAdjlastAdj"
+const _scoreAdjustTyp_name = "panicPathAdjinitFuncAdjinLoopAdjpassConstToIfAdjpassConstToNestedIfAdjpassConcreteToItfCallAdjpassConcreteToNestedItfCallAdjpassFuncToIndCallAdjpassFuncToNestedIndCallAdjpassInlinableFuncToIndCallAdjpassInlinableFuncToNestedIndCallAdjcallResultRescoreAdjlastAdj"
 
-var _scoreAdjustTyp_index = [...]uint8{0, 12, 23, 32, 48, 70, 94, 124, 144, 170, 199, 234, 241}
+var _scoreAdjustTyp_index = [...]uint16{0, 12, 23, 32, 48, 70, 94, 124, 144, 170, 199, 234, 254, 261}
 
 func (i scoreAdjustTyp) String() string {
 	var b bytes.Buffer

src/cmd/compile/internal/inline/inlheur/scoring.go

@@ -31,7 +31,8 @@ const (
 	passFuncToNestedIndCallAdj
 	passInlinableFuncToIndCallAdj
 	passInlinableFuncToNestedIndCallAdj
-	lastAdj scoreAdjustTyp = passInlinableFuncToNestedIndCallAdj
+	callResultRescoreAdj
+	lastAdj scoreAdjustTyp = callResultRescoreAdj
 )
 
 // This table records the specific values we use to adjust call
@@ -52,6 +53,7 @@ var adjValues = map[scoreAdjustTyp]int{
 	passFuncToNestedIndCallAdj:          -20,
 	passInlinableFuncToIndCallAdj:       -45,
 	passInlinableFuncToNestedIndCallAdj: -40,
+	callResultRescoreAdj:                0,
 }
 
 func adjValue(x scoreAdjustTyp) int {

src/cmd/compile/internal/inline/inlheur/testdata/props/returns2.go

@@ -0,0 +1,228 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// DO NOT EDIT (use 'go test -v -update-expected' instead.)
+// See cmd/compile/internal/inline/inlheur/testdata/props/README.txt
+// for more information on the format of this file.
+// <endfilepreamble>
+
+package returns2
+
+// returns2.go T_return_feeds_iface_call 18 0 1
+// <endpropsdump>
+// {"Flags":0,"ParamFlags":[],"ResultFlags":[]}
+// callsite: returns2.go:19:13|0 flagstr "" flagval 0 score -4 mask 2080 maskstr "passConcreteToItfCallAdj|callResultRescoreAdj"
+// <endcallsites>
+// <endfuncpreamble>
+func T_return_feeds_iface_call() {
+	b := newBar(10)
+	b.Plark()
+}
+
+// returns2.go T_multi_return_feeds_iface_call 29 0 1
+// <endpropsdump>
+// {"Flags":0,"ParamFlags":[],"ResultFlags":[]}
+// callsite: returns2.go:30:20|0 flagstr "" flagval 0 score -2 mask 2080 maskstr "passConcreteToItfCallAdj|callResultRescoreAdj"
+// <endcallsites>
+// <endfuncpreamble>
+func T_multi_return_feeds_iface_call() {
+	_, b, _ := newBar2(10)
+	b.Plark()
+}
+
+// returns2.go T_returned_inlinable_func_feeds_indirect_call 41 0 1
+// <endpropsdump>
+// {"Flags":0,"ParamFlags":[0],"ResultFlags":[]}
+// callsite: returns2.go:42:18|0 flagstr "" flagval 0 score -43 mask 2560 maskstr "passInlinableFuncToIndCallAdj|callResultRescoreAdj"
+// callsite: returns2.go:44:20|1 flagstr "" flagval 0 score -28 mask 2560 maskstr "passInlinableFuncToIndCallAdj|callResultRescoreAdj"
+// <endcallsites>
+// <endfuncpreamble>
+func T_returned_inlinable_func_feeds_indirect_call(q int) {
+	f := returnsFunc()
+	f(q)
+	f2 := returnsFunc2()
+	f2(q)
+}
+
+// returns2.go T_returned_noninlineable_func_feeds_indirect_call 54 0 1
+// <endpropsdump>
+// {"Flags":0,"ParamFlags":[0],"ResultFlags":[]}
+// callsite: returns2.go:55:30|0 flagstr "" flagval 0 score -23 mask 2176 maskstr "passFuncToIndCallAdj|callResultRescoreAdj"
+// <endcallsites>
+// <endfuncpreamble>
+func T_returned_noninlineable_func_feeds_indirect_call(q int) {
+	f := returnsNonInlinableFunc()
+	f(q)
+}
+
+// returns2.go T_multi_return_feeds_indirect_call 65 0 1
+// <endpropsdump>
+// {"Flags":0,"ParamFlags":[0],"ResultFlags":[]}
+// callsite: returns2.go:66:29|0 flagstr "" flagval 0 score -26 mask 2560 maskstr "passInlinableFuncToIndCallAdj|callResultRescoreAdj"
+// <endcallsites>
+// <endfuncpreamble>
+func T_multi_return_feeds_indirect_call(q int) {
+	_, f, _ := multiReturnsFunc()
+	f(q)
+}
+
+// returns2.go T_return_feeds_ifswitch 76 0 1
+// <endpropsdump>
+// {"Flags":0,"ParamFlags":[0],"ResultFlags":[0]}
+// callsite: returns2.go:77:14|0 flagstr "" flagval 0 score 5 mask 2056 maskstr "passConstToIfAdj|callResultRescoreAdj"
+// <endcallsites>
+// <endfuncpreamble>
+func T_return_feeds_ifswitch(q int) int {
+	x := meaning(q)
+	if x < 42 {
+		switch x {
+		case 42:
+			return 1
+		}
+	}
+	return 0
+}
+
+// returns2.go T_multi_return_feeds_ifswitch 93 0 1
+// <endpropsdump>
+// {"Flags":0,"ParamFlags":[0],"ResultFlags":[0]}
+// callsite: returns2.go:94:21|0 flagstr "" flagval 0 score 4 mask 2056 maskstr "passConstToIfAdj|callResultRescoreAdj"
+// <endcallsites>
+// <endfuncpreamble>
+func T_multi_return_feeds_ifswitch(q int) int {
+	x, y, z := meanings(q)
+	if x < y {
+		switch x {
+		case 42:
+			return z
+		}
+	}
+	return 0
+}
+
+// returns2.go T_two_calls_feed_ifswitch 111 0 1
+// <endpropsdump>
+// {"Flags":0,"ParamFlags":[0],"ResultFlags":[0]}
+// callsite: returns2.go:115:14|0 flagstr "" flagval 0 score 25 mask 0 maskstr ""
+// callsite: returns2.go:116:14|1 flagstr "" flagval 0 score 25 mask 0 maskstr ""
+// <endcallsites>
+// <endfuncpreamble>
+func T_two_calls_feed_ifswitch(q int) int {
+	// This case we don't handle; for the heuristic to kick in,
+	// all names in a given if/switch cond have to come from the
+	// same callsite
+	x := meaning(q)
+	y := meaning(-q)
+	if x < y {
+		switch x + y {
+		case 42:
+			return 1
+		}
+	}
+	return 0
+}
+
+// returns2.go T_chained_indirect_call 132 0 1
+// <endpropsdump>
+// {"Flags":0,"ParamFlags":[0,0],"ResultFlags":[]}
+// callsite: returns2.go:135:18|0 flagstr "" flagval 0 score -43 mask 2560 maskstr "passInlinableFuncToIndCallAdj|callResultRescoreAdj"
+// <endcallsites>
+// <endfuncpreamble>
+func T_chained_indirect_call(x, y int) {
+	// Here 'returnsFunc' returns an inlinable func that feeds
+	// directly into a call (no named intermediate).
+	G += returnsFunc()(x + y)
+}
+
+// returns2.go T_chained_conc_iface_call 144 0 1
+// <endpropsdump>
+// {"Flags":0,"ParamFlags":[0,0],"ResultFlags":[]}
+// callsite: returns2.go:148:8|0 flagstr "" flagval 0 score -4 mask 2080 maskstr "passConcreteToItfCallAdj|callResultRescoreAdj"
+// <endcallsites>
+// <endfuncpreamble>
+func T_chained_conc_iface_call(x, y int) {
+	// Similar to the case above, return from call returning concrete type
+	// feeds directly into interface call. Note that only the first
+	// iface call is interesting here.
+	newBar(10).Plark().Plark()
+}
+
+func returnsFunc() func(int) int {
+	return adder
+}
+
+func returnsFunc2() func(int) int {
+	return func(x int) int {
+		return adder(x)
+	}
+}
+
+func returnsNonInlinableFunc() func(int) int {
+	return adderNoInline
+}
+
+func multiReturnsFunc() (int, func(int) int, int) {
+	return 42, func(x int) int { G++; return 1 }, -42
+}
+
+func adder(x int) int {
+	G += 1
+	return G
+}
+
+func adderNoInline(x int) int {
+	defer func() { G += x }()
+	G += 1
+	return G
+}
+
+func meaning(q int) int {
+	r := 0
+	for i := 0; i < 42; i++ {
+		r += q
+	}
+	G += r
+	return 42
+}
+
+func meanings(q int) (int, int, int) {
+	r := 0
+	for i := 0; i < 42; i++ {
+		r += q
+	}
+	return 42, 43, r
+}
+
+type Bar struct {
+	x int
+	y string
+}
+
+func (b *Bar) Plark() Itf {
+	return b
+}
+
+type Itf interface {
+	Plark() Itf
+}
+
+func newBar(x int) Itf {
+	s := 0
+	for i := 0; i < x; i++ {
+		s += i
+	}
+	return &Bar{
+		x: s,
+	}
+}
+
+func newBar2(x int) (int, Itf, bool) {
+	s := 0
+	for i := 0; i < x; i++ {
+		s += i
+	}
+	return 0, &Bar{x: s}, false
+}
+
+var G int