[dev.typeparams] all: merge dev.regabi (7e0a81d) into dev.typeparams

As with CL 285875, this required resolving some conflicts around
handling of //go:embed directives. Still further work is needed to
reject uses of //go:embed in files that don't import "embed", so this
is left as a TODO. (When this code was written for dev.typeparams, we
were still leaning towards not requiring the "embed" import.)

Also, the recent support for inlining closures (CL 283112) interacts
poorly with -G=3 mode. There are some known issues with this code
already (#43818), so for now this CL disables inlining of closures
when in -G=3 mode with a TODO to revisit this once closure inlining is
working fully.

Conflicts:

- src/cmd/compile/internal/noder/noder.go
- src/cmd/compile/internal/typecheck/dcl.go
- src/cmd/compile/internal/typecheck/func.go
- test/run.go

Merge List:

+ 2021-01-22 7e0a81d280 [dev.regabi] all: merge master (dab3e5a) into dev.regabi
+ 2021-01-22 dab3e5affe runtime: switch runtime to libc for openbsd/amd64
+ 2021-01-22 a1b53d85da cmd/go: add documentation for test and xtest fields output by go list
+ 2021-01-22 b268b60774 runtime: remove pthread_kill/pthread_self for openbsd
+ 2021-01-22 ec4051763d runtime: fix typo in mgcscavenge.go
+ 2021-01-22 7ece3a7b17 net/http: fix flaky TestDisableKeepAliveUpgrade
+ 2021-01-22 50cba0506f time: clarify Timer.Reset behavior on AfterFunc Timers
+ 2021-01-22 cf10e69f17 doc/go1.16: mention net/http.Transport.GetProxyConnectHeader
+ 2021-01-22 ec1b945265 doc/go1.16: mention path/filepath.WalkDir
+ 2021-01-22 11def3d40b doc/go1.16: mention syscall.AllThreadsSyscall
+ 2021-01-21 07b0235609 doc/go1.16: add notes about package-specific fs.FS changes
+ 2021-01-21 e2b4f1fea5 doc/go1.16: minor formatting fix
+ 2021-01-21 9f43a9e07b doc/go1.16: mention new debug/elf constants
+ 2021-01-21 3c2f11ba5b cmd/go: overwrite program name with full path
+ 2021-01-21 953d1feca9 all: introduce and use internal/execabs
+ 2021-01-21 b186e4d70d cmd/go: add test case for cgo CC setting
+ 2021-01-21 5a8a2265fb cmd/cgo: report exec errors a bit more clearly
+ 2021-01-21 46e2e2e9d9 cmd/go: pass resolved CC, GCCGO to cgo
+ 2021-01-21 3d40895e36 runtime: switch openbsd/arm64 to pthreads
+ 2021-01-21 d95ca91380 crypto/elliptic: fix P-224 field reduction
+ 2021-01-21 d7e71c01ad [dev.regabi] cmd/compile: replace ir.Name map with ir.NameSet for dwarf
+ 2021-01-21 5248f59a22 [dev.regabi] cmd/compile: replace ir.Name map with ir.NameSet for SSA
+ 2021-01-21 970d8b6cb2 [dev.regabi] cmd/compile: replace ir.Name map with ir.NameSet in inlining
+ 2021-01-21 68a4664475 [dev.regabi] cmd/compile: remove tempAssigns in walkCall1
+ 2021-01-21 fd9a391cdd [dev.regabi] cmd/compile: remove CallExpr.Rargs
+ 2021-01-21 19a6db6b63 [dev.regabi] cmd/compile: make sure mkcall* passed non-nil init
+ 2021-01-21 9f036844db [dev.regabi] cmd/compile: use ir.DoChildren directly in inlining
+ 2021-01-21 213c3905e9 [dev.regabi] cmd/compile: use node walked flag to prevent double walk for walkSelect
+ 2021-01-20 1760d736f6 [dev.regabi] cmd/compile: exporting, importing, and inlining functions with OCLOSURE
+ 2021-01-20 ecf4ebf100 cmd/internal/moddeps: check content of all modules in GOROOT
+ 2021-01-20 92cb157cf3 [dev.regabi] cmd/compile: late expansion of return values
+ 2021-01-20 d2d155d1ae runtime: don't adjust timer pp field in timerWaiting status
+ 2021-01-20 803d18fc6c cmd/go: set Incomplete field on go list output if no files match embed
+ 2021-01-20 6e243ce71d cmd/go: have go mod vendor copy embedded files in subdirs
+ 2021-01-20 be28e5abc5 cmd/go: fix mod_get_fallback test
+ 2021-01-20 928bda4f4a runtime: convert openbsd/amd64 locking to libc
+ 2021-01-19 824f2d635c cmd/go: allow go fmt to complete when embedded file is missing
+ 2021-01-19 0575e35e50 cmd/compile: require 'go 1.16' go.mod line for //go:embed
+ 2021-01-19 9423d50d53 [dev.regabi] cmd/compile: use '%q' for printing rune values less than 128
+ 2021-01-19 ccb2e90688 cmd/link: exit before Asmb2 if error
+ 2021-01-19 ca5774a5a5 embed: treat uninitialized FS as empty
+ 2021-01-19 d047c91a6c cmd/link,runtime: switch openbsd/amd64 to pthreads
+ 2021-01-19 61debffd97 runtime: factor out usesLibcall
+ 2021-01-19 9fed39d281 runtime: factor out mStackIsSystemAllocated
+ 2021-01-19 a2f825c542 [dev.regabi] cmd/compile: directly create go.map and go.track symbols
+ 2021-01-19 4a4212c0e5 [dev.regabi] cmd/compile: refactor Linksym creation
+ 2021-01-19 4f5c603c0f [dev.regabi] cmd/compile: cleanup callTargetLSym
+ 2021-01-18 dbab079835 runtime: free Windows event handles after last lock is dropped
+ 2021-01-18 5a8fbb0d2d os: do not close syscall.Stdin in TestReadStdin
+ 2021-01-18 422f38fb6c [dev.regabi] cmd/compile: move stack objects to liveness
+ 2021-01-18 6113db0bb4 [dev.regabi] cmd/compile: convert OPANIC argument to interface{} during typecheck
+ 2021-01-18 4c835f9169 [dev.regabi] cmd/compile: use LinksymOffsetExpr in TypePtr/ItabAddr
+ 2021-01-18 0ffa1ead6e [dev.regabi] cmd/compile: use *obj.LSym instead of *ir.Name for staticdata functions
+ 2021-01-17 7e0fa38aad [dev.regabi] cmd/compile: remove unneeded packages from ir.Pkgs
+ 2021-01-17 99a5db11ac [dev.regabi] cmd/compile: use LinksymOffsetExpr in walkConvInterface
+ 2021-01-17 87845d14f9 [dev.regabi] cmd/compile: add ir.TailCallStmt
+ 2021-01-17 e3027c6828 [dev.regabi] cmd/compile: fix linux-amd64-noopt builder
+ 2021-01-17 59ff93fe64 [dev.regabi] cmd/compile: rename NameOffsetExpr to LinksymOffsetExpr
+ 2021-01-17 82b9cae700 [dev.regabi] cmd/compile: change ir.NameOffsetExpr to use *obj.LSym instead of *Name
+ 2021-01-17 88956fc4b1 [dev.regabi] cmd/compile: stop analyze NameOffsetExpr.Name_ in escape analysis
+ 2021-01-17 7ce2a8383d [dev.regabi] cmd/compile: simplify stack temp initialization
+ 2021-01-17 ba0e8a92fa [dev.regabi] cmd/compile: refactor temp construction in walk
+ 2021-01-17 78e5aabcdb [dev.regabi] cmd/compile: replace Node.HasCall with walk.mayCall
+ 2021-01-16 6de9423445 [dev.regabi] cmd/compile: cleanup OAS2FUNC ordering
+ 2021-01-16 a956a0e909 [dev.regabi] cmd/compile, runtime: fix up comments/error messages from recent renames
+ 2021-01-16 ab3b67abfd [dev.regabi] cmd/compile: remove ONEWOBJ
+ 2021-01-16 c9b1445ac8 [dev.regabi] cmd/compile: remove TypeAssertExpr {Src,Dst}Type fields
+ 2021-01-15 682a1d2176 runtime: detect errors in DuplicateHandle
+ 2021-01-15 9f83418b83 cmd/link: remove GOROOT write in TestBuildForTvOS
+ 2021-01-15 ec9470162f cmd/compile: allow embed into any string or byte slice type
+ 2021-01-15 54198b04db cmd/compile: disallow embed of var inside func
+ 2021-01-15 b386c735e7 cmd/go: fix go generate docs
+ 2021-01-15 bb5075a525 syscall: remove RtlGenRandom and move it into internal/syscall
+ 2021-01-15 1deae0b597 os: invoke processKiller synchronously in testKillProcess
+ 2021-01-15 03a875137f [dev.regabi] cmd/compile: unexport reflectdata.WriteType
+ 2021-01-15 14537e6e54 [dev.regabi] cmd/compile: move stkobj symbol generation to SSA
+ 2021-01-15 ab523fc510 [dev.regabi] cmd/compile: don't promote Byval CaptureVars if Addrtaken
+ 2021-01-15 ff196c3e84 crypto/x509: update iOS bundled roots to version 55188.40.9
+ 2021-01-15 b7a698c73f [dev.regabi] test: disable test on windows because expected contains path separators.
+ 2021-01-15 4be7af23f9 [dev.regabi] cmd/compile: fix ICE during ir.Dump
+ 2021-01-14 e125ccd10e cmd/go: in 'go mod edit', validate versions given to -retract and -exclude
+ 2021-01-14 eb330020dc cmd/dist, cmd/go: pass -arch for C compilation on Darwin
+ 2021-01-14 84e8a06f62 cmd/cgo: remove unnecessary space in cgo export header
+ 2021-01-14 0c86b999c3 cmd/test2json: document passing -test.paniconexit0
+ 2021-01-14 9135795891 cmd/go/internal/load: report positions for embed errors
+ 2021-01-14 35b9c66601 [dev.regabi] cmd/compile,cmd/link: additional code review suggestions for CL 270863
+ 2021-01-14 d9b79e53bb cmd/compile: fix wrong complement for arm64 floating-point comparisons
+ 2021-01-14 c73232d08f cmd/go/internal/load: refactor setErrorPos to PackageError.setPos
+ 2021-01-14 6aa28d3e06 go/build: report positions for go:embed directives
+ 2021-01-14 9734fd482d [dev.regabi] cmd/compile: use node walked flag to prevent double walk for walkSwitch
+ 2021-01-14 f97983249a [dev.regabi] cmd/compile: move more PAUTOHEAP to SSA construction
+ 2021-01-14 4476300425 [dev.regabi] cmd/compile: use byte for CallExpr.Use
+ 2021-01-14 5a5ab24689 [dev.regabi] cmd/compile: do not rely on CallExpr.Rargs for detect already walked calls
+ 2021-01-14 983ac4b086 [dev.regabi] cmd/compile: fix ICE when initializing blank vars
+ 2021-01-13 7eb31d999c cmd/go: add hints to more missing sum error messages
+ 2021-01-13 d6d4673728 [dev.regabi] cmd/compile: fix GOEXPERIMENT=regabi builder
+ 2021-01-13 c41b999ad4 [dev.regabi] cmd/compile: refactor abiutils from "gc" into new "abi"
+ 2021-01-13 861707a8c8 [dev.regabi] cmd/compile: added limited //go:registerparams pragma for new ABI dev
+ 2021-01-13 c1370e918f [dev.regabi] cmd/compile: add code to support register ABI spills around morestack calls
+ 2021-01-13 2abd24f3b7 [dev.regabi] test: make run.go error messages slightly more informative
+ 2021-01-13 9a19481acb [dev.regabi] cmd/compile: make ordering for InvertFlags more stable
+ 2021-01-12 ba76567bc2 cmd/go/internal/modload: delete unused *mvsReqs.next method
+ 2021-01-12 665def2c11 encoding/asn1: document unmarshaling behavior for IMPLICIT string fields
+ 2021-01-11 81ea89adf3 cmd/go: fix non-script staleness checks interacting badly with GOFLAGS
+ 2021-01-11 759309029f doc: update editors.html for Go 1.16
+ 2021-01-11 c3b4c7093a cmd/internal/objfile: don't require runtime.symtab symbol for XCOFF
+ 2021-01-08 59bfc18e34 cmd/go: add hint to read 'go help vcs' to GOVCS errors
+ 2021-01-08 cd6f3a54e4 cmd/go: revise 'go help' documentation for modules
+ 2021-01-08 6192b98751 cmd/go: make hints in error messages more consistent
+ 2021-01-08 25886cf4bd cmd/go: preserve sums for indirect deps fetched by 'go mod download'
+ 2021-01-08 6250833911 runtime/metrics: mark histogram metrics as cumulative
+ 2021-01-08 8f6a9acbb3 runtime/metrics: remove unused StopTheWorld Description field
+ 2021-01-08 6598c65646 cmd/compile: fix exponential-time init-cycle reporting
+ 2021-01-08 fefad1dc85 test: fix timeout code for invoking compiler
+ 2021-01-08 6728118e0a cmd/go: pass signals forward during "go tool"
+ 2021-01-08 e65c543f3c go/build/constraint: add parser for build tag constraint expressions
+ 2021-01-08 0c5afc4fb7 testing/fstest,os: clarify racy behavior of TestFS
+ 2021-01-08 32afcc9436 runtime/metrics: change unit on *-by-size metrics to match bucket unit
+ 2021-01-08 c6513bca5a io/fs: minor corrections to Glob doc
+ 2021-01-08 304f769ffc cmd/compile: don't short-circuit copies whose source is volatile
+ 2021-01-08 ae97717133 runtime,runtime/metrics: use explicit histogram boundaries
+ 2021-01-08 a9ccd2d795 go/build: skip string literal while findEmbed
+ 2021-01-08 d92f8add32 archive/tar: fix typo in comment
+ 2021-01-08 cab1202183 cmd/link: accept extra blocks in TestFallocate
+ 2021-01-08 ee4d32249b io/fs: minor corrections to Glob release date
+ 2021-01-08 54bd1ccce2 cmd: update to latest golang.org/x/tools
+ 2021-01-07 9ec21a8f34 Revert "reflect: support multiple keys in struct tags"
+ 2021-01-07 091414b5b7 io/fs: correct WalkDirFunc documentation
+ 2021-01-07 9b55088d6b doc/go1.16: add release note for disallowing non-ASCII import paths
+ 2021-01-07 fa90aaca7d cmd/compile: fix late expand_calls leaf type for OpStructSelect/OpArraySelect
+ 2021-01-07 7cee66d4cb cmd/go: add documentation for Embed fields in go list output
+ 2021-01-07 e60cffa4ca html/template: attach functions to namespace
+ 2021-01-07 6da2d3b7d7 cmd/link: fix typo in asm.go
+ 2021-01-07 df81a15819 runtime: check mips64 VDSO clock_gettime return code
+ 2021-01-06 4787e906cf crypto/x509: rollback new CertificateRequest fields
+ 2021-01-06 c9658bee93 cmd/go: make module suggestion more friendly
+ 2021-01-06 4c668b25c6 runtime/metrics: fix panic message for Float64Histogram
+ 2021-01-06 d2131704a6 net/http/httputil: fix deadlock in DumpRequestOut
+ 2021-01-05 3e1e13ce6d cmd/go: set cfg.BuildMod to "readonly" by default with no module root
+ 2021-01-05 0b0d004983 cmd/go: pass embedcfg to gccgo if supported
+ 2021-01-05 1b85e7c057 cmd/go: don't scan gccgo standard library packages for imports
+ 2021-01-05 6b37b15d95 runtime: don't take allglock in tracebackothers
+ 2021-01-04 9eef49cfa6 math/rand: fix typo in comment
+ 2021-01-04 b01fb2af9e testing/fstest: fix typo in error message
+ 2021-01-01 3dd5867605 doc: 2021 is the Year of the Gopher
+ 2020-12-31 95ce805d14 io/fs: remove darwin/arm64 special condition
+ 2020-12-30 20d0991b86 lib/time, time/tzdata: update tzdata to 2020f
+ 2020-12-30 ed301733bb misc/cgo/testcarchive: remove special flags for Darwin/ARM
+ 2020-12-30 0ae2e032f2 misc/cgo/test: enable TestCrossPackageTests on darwin/arm64
+ 2020-12-29 780b4de16b misc/ios: fix wording for command line instructions
+ 2020-12-29 b4a71c95d2 doc/go1.16: reference misc/ios/README for how to build iOS programs
+ 2020-12-29 f83e0f6616 misc/ios: add to README how to build ios executables
+ 2020-12-28 4fd9455882 io/fs: fix typo in comment

Change-Id: If24bb93f1e1e7deb1d92ba223c85940ab93b2732

1 files changed, 291 insertions, 81 deletions

diff --git a/src/cmd/compile/internal/inline/inl.go b/src/cmd/compile/internal/inline/inl.go
index 6f5f6499ce..f0be169f56 100644
--- a/src/cmd/compile/internal/inline/inl.go
+++ b/src/cmd/compile/internal/inline/inl.go
@@ -4,7 +4,7 @@
 //
 // The inlining facility makes 2 passes: first caninl determines which
 // functions are suitable for inlining, and for those that are it
-// saves a copy of the body. Then inlcalls walks each function body to
+// saves a copy of the body. Then InlineCalls walks each function body to
 // expand calls to inlinable functions.
 //
 // The Debug.l flag controls the aggressiveness. Note that main() swaps level 0 and 1,
@@ -27,7 +27,6 @@
 package inline
 
 import (
-	"errors"
 	"fmt"
 	"go/constant"
 	"strings"
@@ -74,12 +73,12 @@ func InlinePackage() {
 	})
 }
 
-// Caninl determines whether fn is inlineable.
+// CanInline determines whether fn is inlineable.
 // If so, CanInline saves fn->nbody in fn->inl and substitutes it with a copy.
 // fn and ->nbody will already have been typechecked.
 func CanInline(fn *ir.Func) {
 	if fn.Nname == nil {
-		base.Fatalf("caninl no nname %+v", fn)
+		base.Fatalf("CanInline no nname %+v", fn)
 	}
 
 	var reason string // reason, if any, that the function was not inlined
@@ -144,7 +143,7 @@ func CanInline(fn *ir.Func) {
 	}
 
 	if fn.Typecheck() == 0 {
-		base.Fatalf("caninl on non-typechecked function %v", fn)
+		base.Fatalf("CanInline on non-typechecked function %v", fn)
 	}
 
 	n := fn.Nname
@@ -170,7 +169,6 @@ func CanInline(fn *ir.Func) {
 	visitor := hairyVisitor{
 		budget:        inlineMaxBudget,
 		extraCallCost: cc,
-		usedLocals:    make(map[*ir.Name]bool),
 	}
 	if visitor.tooHairy(fn) {
 		reason = visitor.reason
@@ -180,7 +178,7 @@ func CanInline(fn *ir.Func) {
 	n.Func.Inl = &ir.Inline{
 		Cost: inlineMaxBudget - visitor.budget,
 		Dcl:  pruneUnusedAutos(n.Defn.(*ir.Func).Dcl, &visitor),
-		Body: ir.DeepCopyList(src.NoXPos, fn.Body),
+		Body: inlcopylist(fn.Body),
 	}
 
 	if base.Flag.LowerM > 1 {
@@ -200,11 +198,11 @@ func Inline_Flood(n *ir.Name, exportsym func(*ir.Name)) {
 		return
 	}
 	if n.Op() != ir.ONAME || n.Class != ir.PFUNC {
-		base.Fatalf("inlFlood: unexpected %v, %v, %v", n, n.Op(), n.Class)
+		base.Fatalf("Inline_Flood: unexpected %v, %v, %v", n, n.Op(), n.Class)
 	}
 	fn := n.Func
 	if fn == nil {
-		base.Fatalf("inlFlood: missing Func on %v", n)
+		base.Fatalf("Inline_Flood: missing Func on %v", n)
 	}
 	if fn.Inl == nil {
 		return
@@ -217,10 +215,8 @@ func Inline_Flood(n *ir.Name, exportsym func(*ir.Name)) {
 
 	typecheck.ImportedBody(fn)
 
-	// Recursively identify all referenced functions for
-	// reexport. We want to include even non-called functions,
-	// because after inlining they might be callable.
-	ir.VisitList(ir.Nodes(fn.Inl.Body), func(n ir.Node) {
+	var doFlood func(n ir.Node)
+	doFlood = func(n ir.Node) {
 		switch n.Op() {
 		case ir.OMETHEXPR, ir.ODOTMETH:
 			Inline_Flood(ir.MethodExprName(n), exportsym)
@@ -239,15 +235,16 @@ func Inline_Flood(n *ir.Name, exportsym func(*ir.Name)) {
 			// Okay, because we don't yet inline indirect
 			// calls to method values.
 		case ir.OCLOSURE:
-			// If the closure is inlinable, we'll need to
-			// flood it too. But today we don't support
-			// inlining functions that contain closures.
-			//
-			// When we do, we'll probably want:
-			//     inlFlood(n.Func.Closure.Func.Nname)
-			base.Fatalf("unexpected closure in inlinable function")
+			// VisitList doesn't visit closure bodies, so force a
+			// recursive call to VisitList on the body of the closure.
+			ir.VisitList(n.(*ir.ClosureExpr).Func.Body, doFlood)
 		}
-	})
+	}
+
+	// Recursively identify all referenced functions for
+	// reexport. We want to include even non-called functions,
+	// because after inlining they might be callable.
+	ir.VisitList(ir.Nodes(fn.Inl.Body), doFlood)
 }
 
 // hairyVisitor visits a function body to determine its inlining
@@ -256,18 +253,13 @@ type hairyVisitor struct {
 	budget        int32
 	reason        string
 	extraCallCost int32
-	usedLocals    map[*ir.Name]bool
-	do            func(ir.Node) error
+	usedLocals    ir.NameSet
+	do            func(ir.Node) bool
 }
 
-var errBudget = errors.New("too expensive")
-
 func (v *hairyVisitor) tooHairy(fn *ir.Func) bool {
 	v.do = v.doNode // cache closure
-
-	err := errChildren(fn, v.do)
-	if err != nil {
-		v.reason = err.Error()
+	if ir.DoChildren(fn, v.do) {
 		return true
 	}
 	if v.budget < 0 {
@@ -277,11 +269,10 @@ func (v *hairyVisitor) tooHairy(fn *ir.Func) bool {
 	return false
 }
 
-func (v *hairyVisitor) doNode(n ir.Node) error {
+func (v *hairyVisitor) doNode(n ir.Node) bool {
 	if n == nil {
-		return nil
+		return false
 	}
-
 	switch n.Op() {
 	// Call is okay if inlinable and we have the budget for the body.
 	case ir.OCALLFUNC:
@@ -295,7 +286,8 @@ func (v *hairyVisitor) doNode(n ir.Node) error {
 			if name.Class == ir.PFUNC && types.IsRuntimePkg(name.Sym().Pkg) {
 				fn := name.Sym().Name
 				if fn == "getcallerpc" || fn == "getcallersp" {
-					return errors.New("call to " + fn)
+					v.reason = "call to " + fn
+					return true
 				}
 				if fn == "throw" {
 					v.budget -= inlineExtraThrowCost
@@ -346,38 +338,61 @@ func (v *hairyVisitor) doNode(n ir.Node) error {
 		v.budget -= v.extraCallCost
 
 	case ir.OPANIC:
+		n := n.(*ir.UnaryExpr)
+		if n.X.Op() == ir.OCONVIFACE && n.X.(*ir.ConvExpr).Implicit() {
+			// Hack to keep reflect.flag.mustBe inlinable for TestIntendedInlining.
+			// Before CL 284412, these conversions were introduced later in the
+			// compiler, so they didn't count against inlining budget.
+			v.budget++
+		}
 		v.budget -= inlineExtraPanicCost
 
 	case ir.ORECOVER:
 		// recover matches the argument frame pointer to find
 		// the right panic value, so it needs an argument frame.
-		return errors.New("call to recover")
+		v.reason = "call to recover"
+		return true
+
+	case ir.OCLOSURE:
+		// TODO(danscales,mdempsky): Get working with -G.
+		// Probably after #43818 is fixed.
+		if base.Flag.G > 0 {
+			v.reason = "inlining closures not yet working with -G"
+			return true
+		}
 
-	case ir.OCLOSURE,
-		ir.ORANGE,
+		// TODO(danscales) - fix some bugs when budget is lowered below 30
+		// Maybe make budget proportional to number of closure variables, e.g.:
+		//v.budget -= int32(len(n.(*ir.ClosureExpr).Func.ClosureVars) * 3)
+		v.budget -= 30
+
+	case ir.ORANGE,
 		ir.OSELECT,
 		ir.OGO,
 		ir.ODEFER,
 		ir.ODCLTYPE, // can't print yet
-		ir.ORETJMP:
-		return errors.New("unhandled op " + n.Op().String())
+		ir.OTAILCALL:
+		v.reason = "unhandled op " + n.Op().String()
+		return true
 
 	case ir.OAPPEND:
 		v.budget -= inlineExtraAppendCost
 
 	case ir.ODCLCONST, ir.OFALL:
 		// These nodes don't produce code; omit from inlining budget.
-		return nil
+		return false
 
 	case ir.OFOR, ir.OFORUNTIL:
 		n := n.(*ir.ForStmt)
 		if n.Label != nil {
-			return errors.New("labeled control")
+			v.reason = "labeled control"
+			return true
 		}
 	case ir.OSWITCH:
 		n := n.(*ir.SwitchStmt)
 		if n.Label != nil {
-			return errors.New("labeled control")
+			v.reason = "labeled control"
+			return true
 		}
 	// case ir.ORANGE, ir.OSELECT in "unhandled" above
 
@@ -393,22 +408,15 @@ func (v *hairyVisitor) doNode(n ir.Node) error {
 		if ir.IsConst(n.Cond, constant.Bool) {
 			// This if and the condition cost nothing.
 			// TODO(rsc): It seems strange that we visit the dead branch.
-			if err := errList(n.Init(), v.do); err != nil {
-				return err
-			}
-			if err := errList(n.Body, v.do); err != nil {
-				return err
-			}
-			if err := errList(n.Else, v.do); err != nil {
-				return err
-			}
-			return nil
+			return doList(n.Init(), v.do) ||
+				doList(n.Body, v.do) ||
+				doList(n.Else, v.do)
 		}
 
 	case ir.ONAME:
 		n := n.(*ir.Name)
 		if n.Class == ir.PAUTO {
-			v.usedLocals[n] = true
+			v.usedLocals.Add(n)
 		}
 
 	case ir.OBLOCK:
@@ -428,10 +436,11 @@ func (v *hairyVisitor) doNode(n ir.Node) error {
 
 	// When debugging, don't stop early, to get full cost of inlining this function
 	if v.budget < 0 && base.Flag.LowerM < 2 && !logopt.Enabled() {
-		return errBudget
+		v.reason = "too expensive"
+		return true
 	}
 
-	return errChildren(n, v.do)
+	return ir.DoChildren(n, v.do)
 }
 
 func isBigFunc(fn *ir.Func) bool {
@@ -442,6 +451,52 @@ func isBigFunc(fn *ir.Func) bool {
 	})
 }
 
+// inlcopylist (together with inlcopy) recursively copies a list of nodes, except
+// that it keeps the same ONAME, OTYPE, and OLITERAL nodes. It is used for copying
+// the body and dcls of an inlineable function.
+func inlcopylist(ll []ir.Node) []ir.Node {
+	s := make([]ir.Node, len(ll))
+	for i, n := range ll {
+		s[i] = inlcopy(n)
+	}
+	return s
+}
+
+// inlcopy is like DeepCopy(), but does extra work to copy closures.
+func inlcopy(n ir.Node) ir.Node {
+	var edit func(ir.Node) ir.Node
+	edit = func(x ir.Node) ir.Node {
+		switch x.Op() {
+		case ir.ONAME, ir.OTYPE, ir.OLITERAL, ir.ONIL:
+			return x
+		}
+		m := ir.Copy(x)
+		ir.EditChildren(m, edit)
+		if x.Op() == ir.OCLOSURE {
+			x := x.(*ir.ClosureExpr)
+			// Need to save/duplicate x.Func.Nname,
+			// x.Func.Nname.Ntype, x.Func.Dcl, x.Func.ClosureVars, and
+			// x.Func.Body for iexport and local inlining.
+			oldfn := x.Func
+			newfn := ir.NewFunc(oldfn.Pos())
+			if oldfn.ClosureCalled() {
+				newfn.SetClosureCalled(true)
+			}
+			m.(*ir.ClosureExpr).Func = newfn
+			newfn.Nname = ir.NewNameAt(oldfn.Nname.Pos(), oldfn.Nname.Sym())
+			// XXX OK to share fn.Type() ??
+			newfn.Nname.SetType(oldfn.Nname.Type())
+			newfn.Nname.Ntype = inlcopy(oldfn.Nname.Ntype).(ir.Ntype)
+			newfn.Body = inlcopylist(oldfn.Body)
+			// Make shallow copy of the Dcl and ClosureVar slices
+			newfn.Dcl = append([]*ir.Name(nil), oldfn.Dcl...)
+			newfn.ClosureVars = append([]*ir.Name(nil), oldfn.ClosureVars...)
+		}
+		return m
+	}
+	return edit(n)
+}
+
 // Inlcalls/nodelist/node walks fn's statements and expressions and substitutes any
 // calls made to inlineable functions. This is the external entry point.
 func InlineCalls(fn *ir.Func) {
@@ -762,13 +817,6 @@ func mkinlcall(n *ir.CallExpr, fn *ir.Func, maxCost int32, inlMap map[*ir.Func]b
 		if ln.Class == ir.PPARAMOUT { // return values handled below.
 			continue
 		}
-		if ir.IsParamStackCopy(ln) { // ignore the on-stack copy of a parameter that moved to the heap
-			// TODO(mdempsky): Remove once I'm confident
-			// this never actually happens. We currently
-			// perform inlining before escape analysis, so
-			// nothing should have moved to the heap yet.
-			base.Fatalf("impossible: %v", ln)
-		}
 		inlf := typecheck.Expr(inlvar(ln)).(*ir.Name)
 		inlvars[ln] = inlf
 		if base.Flag.GenDwarfInl > 0 {
@@ -925,6 +973,7 @@ func mkinlcall(n *ir.CallExpr, fn *ir.Func, maxCost int32, inlMap map[*ir.Func]b
 		inlvars:      inlvars,
 		bases:        make(map[*src.PosBase]*src.PosBase),
 		newInlIndex:  newIndex,
+		fn:           fn,
 	}
 	subst.edit = subst.node
 
@@ -1031,6 +1080,12 @@ type inlsubst struct {
 	newInlIndex int
 
 	edit func(ir.Node) ir.Node // cached copy of subst.node method value closure
+
+	// If non-nil, we are inside a closure inside the inlined function, and
+	// newclofn is the Func of the new inlined closure.
+	newclofn *ir.Func
+
+	fn *ir.Func // For debug -- the func that is being inlined
 }
 
 // list inlines a list of nodes.
@@ -1042,6 +1097,157 @@ func (subst *inlsubst) list(ll ir.Nodes) []ir.Node {
 	return s
 }
 
+// fields returns a list of the fields of a struct type representing receiver,
+// params, or results, after duplicating the field nodes and substituting the
+// Nname nodes inside the field nodes.
+func (subst *inlsubst) fields(oldt *types.Type) []*types.Field {
+	oldfields := oldt.FieldSlice()
+	newfields := make([]*types.Field, len(oldfields))
+	for i := range oldfields {
+		newfields[i] = oldfields[i].Copy()
+		if oldfields[i].Nname != nil {
+			newfields[i].Nname = subst.node(oldfields[i].Nname.(*ir.Name))
+		}
+	}
+	return newfields
+}
+
+// clovar creates a new ONAME node for a local variable or param of a closure
+// inside a function being inlined.
+func (subst *inlsubst) clovar(n *ir.Name) *ir.Name {
+	// TODO(danscales): want to get rid of this shallow copy, with code like the
+	// following, but it is hard to copy all the necessary flags in a maintainable way.
+	// m := ir.NewNameAt(n.Pos(), n.Sym())
+	// m.Class = n.Class
+	// m.SetType(n.Type())
+	// m.SetTypecheck(1)
+	//if n.IsClosureVar() {
+	//	m.SetIsClosureVar(true)
+	//}
+	m := &ir.Name{}
+	*m = *n
+	m.Curfn = subst.newclofn
+	if n.Defn != nil && n.Defn.Op() == ir.ONAME {
+		if !n.IsClosureVar() {
+			base.FatalfAt(n.Pos(), "want closure variable, got: %+v", n)
+		}
+		if n.Sym().Pkg != types.LocalPkg {
+			// If the closure came from inlining a function from
+			// another package, must change package of captured
+			// variable to localpkg, so that the fields of the closure
+			// struct are local package and can be accessed even if
+			// name is not exported. If you disable this code, you can
+			// reproduce the problem by running 'go test
+			// go/internal/srcimporter'. TODO(mdempsky) - maybe change
+			// how we create closure structs?
+			m.SetSym(types.LocalPkg.Lookup(n.Sym().Name))
+		}
+		// Make sure any inlvar which is the Defn
+		// of an ONAME closure var is rewritten
+		// during inlining. Don't substitute
+		// if Defn node is outside inlined function.
+		if subst.inlvars[n.Defn.(*ir.Name)] != nil {
+			m.Defn = subst.node(n.Defn)
+		}
+	}
+	if n.Outer != nil {
+		// Either the outer variable is defined in function being inlined,
+		// and we will replace it with the substituted variable, or it is
+		// defined outside the function being inlined, and we should just
+		// skip the outer variable (the closure variable of the function
+		// being inlined).
+		s := subst.node(n.Outer).(*ir.Name)
+		if s == n.Outer {
+			s = n.Outer.Outer
+		}
+		m.Outer = s
+	}
+	return m
+}
+
+// closure does the necessary substitions for a ClosureExpr n and returns the new
+// closure node.
+func (subst *inlsubst) closure(n *ir.ClosureExpr) ir.Node {
+	m := ir.Copy(n)
+	m.SetPos(subst.updatedPos(m.Pos()))
+	ir.EditChildren(m, subst.edit)
+
+	//fmt.Printf("Inlining func %v with closure into %v\n", subst.fn, ir.FuncName(ir.CurFunc))
+
+	// The following is similar to funcLit
+	oldfn := n.Func
+	newfn := ir.NewFunc(oldfn.Pos())
+	// These three lines are not strictly necessary, but just to be clear
+	// that new function needs to redo typechecking and inlinability.
+	newfn.SetTypecheck(0)
+	newfn.SetInlinabilityChecked(false)
+	newfn.Inl = nil
+	newfn.SetIsHiddenClosure(true)
+	newfn.Nname = ir.NewNameAt(n.Pos(), ir.BlankNode.Sym())
+	newfn.Nname.Func = newfn
+	newfn.Nname.Ntype = subst.node(oldfn.Nname.Ntype).(ir.Ntype)
+	newfn.Nname.Defn = newfn
+
+	m.(*ir.ClosureExpr).Func = newfn
+	newfn.OClosure = m.(*ir.ClosureExpr)
+
+	if subst.newclofn != nil {
+		//fmt.Printf("Inlining a closure with a nested closure\n")
+	}
+	prevxfunc := subst.newclofn
+
+	// Mark that we are now substituting within a closure (within the
+	// inlined function), and create new nodes for all the local
+	// vars/params inside this closure.
+	subst.newclofn = newfn
+	newfn.Dcl = nil
+	newfn.ClosureVars = nil
+	for _, oldv := range oldfn.Dcl {
+		newv := subst.clovar(oldv)
+		subst.inlvars[oldv] = newv
+		newfn.Dcl = append(newfn.Dcl, newv)
+	}
+	for _, oldv := range oldfn.ClosureVars {
+		newv := subst.clovar(oldv)
+		subst.inlvars[oldv] = newv
+		newfn.ClosureVars = append(newfn.ClosureVars, newv)
+	}
+
+	// Need to replace ONAME nodes in
+	// newfn.Type().FuncType().Receiver/Params/Results.FieldSlice().Nname
+	oldt := oldfn.Type()
+	newrecvs := subst.fields(oldt.Recvs())
+	var newrecv *types.Field
+	if len(newrecvs) > 0 {
+		newrecv = newrecvs[0]
+	}
+	newt := types.NewSignature(oldt.Pkg(), newrecv,
+		subst.fields(oldt.Params()), subst.fields(oldt.Results()))
+
+	newfn.Nname.SetType(newt)
+	newfn.Body = subst.list(oldfn.Body)
+
+	// Remove the nodes for the current closure from subst.inlvars
+	for _, oldv := range oldfn.Dcl {
+		delete(subst.inlvars, oldv)
+	}
+	for _, oldv := range oldfn.ClosureVars {
+		delete(subst.inlvars, oldv)
+	}
+	// Go back to previous closure func
+	subst.newclofn = prevxfunc
+
+	// Actually create the named function for the closure, now that
+	// the closure is inlined in a specific function.
+	m.SetTypecheck(0)
+	if oldfn.ClosureCalled() {
+		typecheck.Callee(m)
+	} else {
+		typecheck.Expr(m)
+	}
+	return m
+}
+
 // node recursively copies a node from the saved pristine body of the
 // inlined function, substituting references to input/output
 // parameters with ones to the tmpnames, and substituting returns with
@@ -1056,13 +1262,17 @@ func (subst *inlsubst) node(n ir.Node) ir.Node {
 		n := n.(*ir.Name)
 
 		// Handle captured variables when inlining closures.
-		if n.IsClosureVar() {
+		if n.IsClosureVar() && subst.newclofn == nil {
 			o := n.Outer
 
+			// Deal with case where sequence of closures are inlined.
+			// TODO(danscales) - write test case to see if we need to
+			// go up multiple levels.
+			if o.Curfn != ir.CurFunc {
+				o = o.Outer
+			}
+
 			// make sure the outer param matches the inlining location
-			// NB: if we enabled inlining of functions containing OCLOSURE or refined
-			// the reassigned check via some sort of copy propagation this would most
-			// likely need to be changed to a loop to walk up to the correct Param
 			if o == nil || o.Curfn != ir.CurFunc {
 				base.Fatalf("%v: unresolvable capture %v\n", ir.Line(n), n)
 			}
@@ -1098,6 +1308,10 @@ func (subst *inlsubst) node(n ir.Node) ir.Node {
 		}
 
 	case ir.ORETURN:
+		if subst.newclofn != nil {
+			// Don't do special substitutions if inside a closure
+			break
+		}
 		// Since we don't handle bodies with closures,
 		// this return is guaranteed to belong to the current inlined function.
 		n := n.(*ir.ReturnStmt)
@@ -1136,6 +1350,10 @@ func (subst *inlsubst) node(n ir.Node) ir.Node {
 		return m
 
 	case ir.OLABEL:
+		if subst.newclofn != nil {
+			// Don't do special substitutions if inside a closure
+			break
+		}
 		n := n.(*ir.LabelStmt)
 		m := ir.Copy(n).(*ir.LabelStmt)
 		m.SetPos(subst.updatedPos(m.Pos()))
@@ -1143,10 +1361,10 @@ func (subst *inlsubst) node(n ir.Node) ir.Node {
 		p := fmt.Sprintf("%s·%d", n.Label.Name, inlgen)
 		m.Label = typecheck.Lookup(p)
 		return m
-	}
 
-	if n.Op() == ir.OCLOSURE {
-		base.Fatalf("cannot inline function containing closure: %+v", n)
+	case ir.OCLOSURE:
+		return subst.closure(n.(*ir.ClosureExpr))
+
 	}
 
 	m := ir.Copy(n)
@@ -1171,7 +1389,7 @@ func pruneUnusedAutos(ll []*ir.Name, vis *hairyVisitor) []*ir.Name {
 	s := make([]*ir.Name, 0, len(ll))
 	for _, n := range ll {
 		if n.Class == ir.PAUTO {
-			if _, found := vis.usedLocals[n]; !found {
+			if !vis.usedLocals.Has(n) {
 				continue
 			}
 		}
@@ -1191,21 +1409,13 @@ func numNonClosures(list []*ir.Func) int {
 	return count
 }
 
-// TODO(mdempsky): Update inl.go to use ir.DoChildren directly.
-func errChildren(n ir.Node, do func(ir.Node) error) (err error) {
-	ir.DoChildren(n, func(x ir.Node) bool {
-		err = do(x)
-		return err != nil
-	})
-	return
-}
-func errList(list []ir.Node, do func(ir.Node) error) error {
+func doList(list []ir.Node, do func(ir.Node) bool) bool {
 	for _, x := range list {
 		if x != nil {
-			if err := do(x); err != nil {
-				return err
+			if do(x) {
+				return true
 			}
 		}
 	}
-	return nil
+	return false
 }