cmd/compile,runtime: remove ambiguously live logic

The previous CL introduced stack objects. This CL removes the old
ambiguously live liveness analysis. After this CL we're relying
on stack objects exclusively.

Update a bunch of liveness tests to reflect the new world.

Fixes #22350

Change-Id: I739b26e015882231011ce6bc1a7f426049e59f31
Reviewed-on: https://go-review.googlesource.com/c/134156
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

7 files changed, 259 insertions, 105 deletions

diff --git a/test/fixedbugs/issue20250.go b/test/fixedbugs/issue20250.go
index 6fc861a8dc..47879385d2 100644
--- a/test/fixedbugs/issue20250.go
+++ b/test/fixedbugs/issue20250.go
@@ -15,10 +15,10 @@ type T struct {
 }
 
 func f(a T) { // ERROR "live at entry to f: a"
-	var e interface{}
-	func() { // ERROR "live at entry to f.func1: a &e"
-		e = a.s // ERROR "live at call to convT2Estring: a &e"
-	}() // ERROR "live at call to f.func1: e$"
+	var e interface{} // ERROR "stack object e interface \{\}$"
+	func() {          // ERROR "live at entry to f.func1: a &e"
+		e = a.s // ERROR "live at call to convT2Estring: &e" "stack object a T$"
+	}()
 	// Before the fix, both a and e were live at the previous line.
 	_ = e
 }
diff --git a/test/live.go b/test/live.go
index 13bdc4aae1..679562d9bf 100644
--- a/test/live.go
+++ b/test/live.go
@@ -32,9 +32,9 @@ func printbytepointer(*byte)
 func printint(int)
 
 func f1() {
-	var x *int
-	printpointer(&x) // ERROR "live at call to printpointer: x$"
+	var x *int       // ERROR "stack object x \*int$"
 	printpointer(&x) // ERROR "live at call to printpointer: x$"
+	printpointer(&x)
 }
 
 func f2(b bool) {
@@ -42,9 +42,9 @@ func f2(b bool) {
 		printint(0) // nothing live here
 		return
 	}
-	var x *int
-	printpointer(&x) // ERROR "live at call to printpointer: x$"
+	var x *int       // ERROR "stack object x \*int$"
 	printpointer(&x) // ERROR "live at call to printpointer: x$"
+	printpointer(&x)
 }
 
 func f3(b1, b2 bool) {
@@ -60,15 +60,15 @@ func f3(b1, b2 bool) {
 	}
 
 	if b2 {
-		var x *int
-		printpointer(&x) // ERROR "live at call to printpointer: x$"
+		var x *int       // ERROR "stack object x \*int$"
 		printpointer(&x) // ERROR "live at call to printpointer: x$"
+		printpointer(&x)
 	} else {
-		var y *int
-		printpointer(&y) // ERROR "live at call to printpointer: y$"
+		var y *int       // ERROR "stack object y \*int$"
 		printpointer(&y) // ERROR "live at call to printpointer: y$"
+		printpointer(&y)
 	}
-	printint(0) // ERROR "f3: x \(type \*int\) is ambiguously live$" "f3: y \(type \*int\) is ambiguously live$" "live at call to printint: x y$"
+	printint(0) // nothing is live here
 }
 
 // The old algorithm treated x as live on all code that
@@ -83,7 +83,7 @@ func f4(b1, b2 bool) { // x not live here
 		return
 	}
 	var z **int
-	x := new(int)
+	x := new(int) // ERROR "stack object x \*int$"
 	*x = 42
 	z = &x
 	printint(**z) // ERROR "live at call to printint: x$"
@@ -99,15 +99,15 @@ func f4(b1, b2 bool) { // x not live here
 func f5(b1 bool) {
 	var z **int
 	if b1 {
-		x := new(int)
+		x := new(int) // ERROR "stack object x \*int$"
 		*x = 42
 		z = &x
 	} else {
-		y := new(int)
+		y := new(int) // ERROR "stack object y \*int$"
 		*y = 54
 		z = &y
 	}
-	printint(**z) // ERROR "f5: x \(type \*int\) is ambiguously live$" "f5: y \(type \*int\) is ambiguously live$" "live at call to printint: x y$"
+	printint(**z) // nothing live here
 }
 
 // confusion about the _ result used to cause spurious "live at entry to f6: _".
@@ -119,7 +119,7 @@ func f6() (_, y string) {
 
 // confusion about addressed results used to cause "live at entry to f7: x".
 
-func f7() (x string) {
+func f7() (x string) { // ERROR "stack object x string"
 	_ = &x
 	x = "hello"
 	return
@@ -141,7 +141,7 @@ var i9 interface{}
 func f9() bool {
 	g8()
 	x := i9
-	y := interface{}(str()) // ERROR "live at call to convT2Estring: .autotmp_[0-9]+ x.data$" "live at call to str: x.data$"
+	y := interface{}(str()) // ERROR "live at call to convT2Estring: x.data$" "live at call to str: x.data$" "stack object .autotmp_[0-9]+ string$"
 	i9 = y                  // make y escape so the line above has to call convT2E
 	return x != y
 }
@@ -163,7 +163,7 @@ var b bool
 
 // this used to have a spurious "live at entry to f11a: ~r0"
 func f11a() *int {
-	select { // ERROR "live at call to selectgo: .autotmp_[0-9]+$"
+	select { // ERROR "stack object .autotmp_[0-9]+ \[2\]struct"
 	case <-c:
 		return nil
 	case <-c:
@@ -178,7 +178,7 @@ func f11b() *int {
 		// get to the bottom of the function.
 		// This used to have a spurious "live at call to printint: p".
 		printint(1) // nothing live here!
-		select {    // ERROR "live at call to selectgo: .autotmp_[0-9]+$"
+		select {    // ERROR "stack object .autotmp_[0-9]+ \[2\]struct"
 		case <-c:
 			return nil
 		case <-c:
@@ -198,7 +198,7 @@ func f11c() *int {
 		// Unlike previous, the cases in this select fall through,
 		// so we can get to the println, so p is not dead.
 		printint(1) // ERROR "live at call to printint: p$"
-		select {    // ERROR "live at call to selectgo: .autotmp_[0-9]+ p$"
+		select {    // ERROR "live at call to selectgo: p$" "stack object .autotmp_[0-9]+ \[2\]struct"
 		case <-c:
 		case <-c:
 		}
@@ -233,8 +233,8 @@ func h13(string, string) string
 // more incorrectly placed VARDEF.
 
 func f14() {
-	x := g14()
-	printstringpointer(&x) // ERROR "live at call to printstringpointer: x$"
+	x := g14() // ERROR "stack object x string$"
+	printstringpointer(&x)
 }
 
 func g14() string
@@ -254,10 +254,10 @@ func iface() interface{}
 
 func f16() {
 	if b {
-		delete(mi, iface()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
+		delete(mi, iface()) // ERROR "stack object .autotmp_[0-9]+ interface \{\}$"
 	}
-	delete(mi, iface()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
-	delete(mi, iface()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
+	delete(mi, iface()) // ERROR "stack object .autotmp_[0-9]+ interface \{\}$"
+	delete(mi, iface()) // ERROR "stack object .autotmp_[0-9]+ interface \{\}$"
 }
 
 var m2s map[string]*byte
@@ -300,10 +300,10 @@ func f18() {
 	// temporary introduced by orderexpr.
 	var z *byte
 	if b {
-		z = m2[g18()] // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+		z = m2[g18()] // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
 	}
-	z = m2[g18()] // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
-	z = m2[g18()] // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+	z = m2[g18()] // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
+	z = m2[g18()] // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
 	printbytepointer(z)
 }
 
@@ -317,30 +317,30 @@ func f19() {
 	var z *byte
 
 	if b {
-		z = <-ch // ERROR "live at call to chanrecv1: .autotmp_[0-9]+$"
+		z = <-ch // ERROR "stack object .autotmp_[0-9]+ \*byte$"
 	}
-	z = <-ch // ERROR "live at call to chanrecv1: .autotmp_[0-9]+$"
-	z = <-ch // ERROR "live at call to chanrecv1: .autotmp_[0-9]+$"
+	z = <-ch // ERROR "stack object .autotmp_[0-9]+ \*byte$"
+	z = <-ch // ERROR "stack object .autotmp_[0-9]+ \*byte$" "live at call to chanrecv1: .autotmp_[0-9]+$"
 	printbytepointer(z)
 }
 
 func f20() {
 	// src temporary for channel send
 	if b {
-		ch <- byteptr() // ERROR "live at call to chansend1: .autotmp_[0-9]+$"
+		ch <- byteptr() // ERROR "stack object .autotmp_[0-9]+ \*byte$"
 	}
-	ch <- byteptr() // ERROR "live at call to chansend1: .autotmp_[0-9]+$"
-	ch <- byteptr() // ERROR "live at call to chansend1: .autotmp_[0-9]+$"
+	ch <- byteptr() // ERROR "stack object .autotmp_[0-9]+ \*byte$"
+	ch <- byteptr() // ERROR "stack object .autotmp_[0-9]+ \*byte$"
 }
 
 func f21() {
 	// key temporary for mapaccess using array literal key.
 	var z *byte
 	if b {
-		z = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+		z = m2[[2]string{"x", "y"}] // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
 	}
-	z = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
-	z = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+	z = m2[[2]string{"x", "y"}] // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
+	z = m2[[2]string{"x", "y"}] // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
 	printbytepointer(z)
 }
 
@@ -349,10 +349,10 @@ func f23() {
 	var z *byte
 	var ok bool
 	if b {
-		z, ok = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess2: .autotmp_[0-9]+$"
+		z, ok = m2[[2]string{"x", "y"}] // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
 	}
-	z, ok = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess2: .autotmp_[0-9]+$"
-	z, ok = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess2: .autotmp_[0-9]+$"
+	z, ok = m2[[2]string{"x", "y"}] // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
+	z, ok = m2[[2]string{"x", "y"}] // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
 	printbytepointer(z)
 	print(ok)
 }
@@ -361,10 +361,10 @@ func f24() {
 	// key temporary for map access using array literal key.
 	// value temporary too.
 	if b {
-		m2[[2]string{"x", "y"}] = nil // ERROR "live at call to mapassign: .autotmp_[0-9]+$"
+		m2[[2]string{"x", "y"}] = nil // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
 	}
-	m2[[2]string{"x", "y"}] = nil // ERROR "live at call to mapassign: .autotmp_[0-9]+$"
-	m2[[2]string{"x", "y"}] = nil // ERROR "live at call to mapassign: .autotmp_[0-9]+$"
+	m2[[2]string{"x", "y"}] = nil // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
+	m2[[2]string{"x", "y"}] = nil // ERROR "stack object .autotmp_[0-9]+ \[2\]string$"
 }
 
 // defer should not cause spurious ambiguously live variables
@@ -387,10 +387,10 @@ func g25()
 
 func f26(b bool) {
 	if b {
-		print26((*int)(nil), (*int)(nil), (*int)(nil)) // ERROR "live at call to print26: .autotmp_[0-9]+$"
+		print26((*int)(nil), (*int)(nil), (*int)(nil)) // ERROR "stack object .autotmp_[0-9]+ \[3\]interface \{\}$"
 	}
-	print26((*int)(nil), (*int)(nil), (*int)(nil)) // ERROR "live at call to print26: .autotmp_[0-9]+$"
-	print26((*int)(nil), (*int)(nil), (*int)(nil)) // ERROR "live at call to print26: .autotmp_[0-9]+$"
+	print26((*int)(nil), (*int)(nil), (*int)(nil)) // ERROR "stack object .autotmp_[0-9]+ \[3\]interface \{\}$"
+	print26((*int)(nil), (*int)(nil), (*int)(nil)) // ERROR "stack object .autotmp_[0-9]+ \[3\]interface \{\}$"
 	printnl()
 }
 
@@ -402,10 +402,10 @@ func print26(...interface{})
 func f27(b bool) {
 	x := 0
 	if b {
-		call27(func() { x++ }) // ERROR "live at call to call27: .autotmp_[0-9]+$"
+		call27(func() { x++ }) // ERROR "stack object .autotmp_[0-9]+ struct \{"
 	}
-	call27(func() { x++ }) // ERROR "live at call to call27: .autotmp_[0-9]+$"
-	call27(func() { x++ }) // ERROR "live at call to call27: .autotmp_[0-9]+$"
+	call27(func() { x++ }) // ERROR "stack object .autotmp_[0-9]+ struct \{"
+	call27(func() { x++ }) // ERROR "stack object .autotmp_[0-9]+ struct \{"
 	printnl()
 }
 
@@ -414,11 +414,11 @@ func f27(b bool) {
 func f27defer(b bool) {
 	x := 0
 	if b {
-		defer call27(func() { x++ }) // ERROR "live at call to deferproc: .autotmp_[0-9]+$" "live at call to deferreturn: .autotmp_[0-9]+$"
+		defer call27(func() { x++ }) // ERROR "stack object .autotmp_[0-9]+ struct \{"
 	}
-	defer call27(func() { x++ }) // ERROR "f27defer: .autotmp_[0-9]+ \(type struct { F uintptr; x \*int }\) is ambiguously live$" "live at call to deferproc: .autotmp_[0-9]+ .autotmp_[0-9]+$" "live at call to deferreturn: .autotmp_[0-9]+ .autotmp_[0-9]+$"
-	printnl()                    // ERROR "live at call to printnl: .autotmp_[0-9]+ .autotmp_[0-9]+$"
-} // ERROR "live at call to deferreturn: .autotmp_[0-9]+ .autotmp_[0-9]+$"
+	defer call27(func() { x++ }) // ERROR "stack object .autotmp_[0-9]+ struct \{"
+	printnl()
+}
 
 // and newproc (go) escapes to the heap
 
@@ -440,24 +440,24 @@ var s1, s2, s3, s4, s5, s6, s7, s8, s9, s10 string
 
 func f28(b bool) {
 	if b {
-		printstring(s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10) // ERROR "live at call to concatstrings: .autotmp_[0-9]+$" "live at call to printstring: .autotmp_[0-9]+$"
+		printstring(s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10) // ERROR "stack object .autotmp_[0-9]+ \[10\]string$"
 	}
-	printstring(s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10) // ERROR "live at call to concatstrings: .autotmp_[0-9]+$" "live at call to printstring: .autotmp_[0-9]+$"
-	printstring(s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10) // ERROR "live at call to concatstrings: .autotmp_[0-9]+$" "live at call to printstring: .autotmp_[0-9]+$"
+	printstring(s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10) // ERROR "stack object .autotmp_[0-9]+ \[10\]string$"
+	printstring(s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10) // ERROR "stack object .autotmp_[0-9]+ \[10\]string$"
 }
 
 // map iterator should die on end of range loop
 
 func f29(b bool) {
 	if b {
-		for k := range m { // ERROR "live at call to mapiterinit: .autotmp_[0-9]+$" "live at call to mapiternext: .autotmp_[0-9]+$"
+		for k := range m { // ERROR "live at call to mapiterinit: .autotmp_[0-9]+$" "live at call to mapiternext: .autotmp_[0-9]+$" "stack object .autotmp_[0-9]+ map.iter\[string\]int$"
 			printstring(k) // ERROR "live at call to printstring: .autotmp_[0-9]+$"
 		}
 	}
-	for k := range m { // ERROR "live at call to mapiterinit: .autotmp_[0-9]+$" "live at call to mapiternext: .autotmp_[0-9]+$"
+	for k := range m { // ERROR "live at call to mapiterinit: .autotmp_[0-9]+$" "live at call to mapiternext: .autotmp_[0-9]+$" "stack object .autotmp_[0-9]+ map.iter\[string\]int$"
 		printstring(k) // ERROR "live at call to printstring: .autotmp_[0-9]+$"
 	}
-	for k := range m { // ERROR "live at call to mapiterinit: .autotmp_[0-9]+$" "live at call to mapiternext: .autotmp_[0-9]+$"
+	for k := range m { // ERROR "live at call to mapiterinit: .autotmp_[0-9]+$" "live at call to mapiternext: .autotmp_[0-9]+$" "stack object .autotmp_[0-9]+ map.iter\[string\]int$"
 		printstring(k) // ERROR "live at call to printstring: .autotmp_[0-9]+$"
 	}
 }
@@ -473,20 +473,19 @@ type pstruct struct {
 }
 
 func f30(b bool) {
-	// two live temps during printintpointer(p):
-	// in the copy of p.intp and
+	// live temp during printintpointer(p):
 	// the internal iterator pointer if a pointer to pstruct in pstructarr
 	// can not be easily computed by strength reduction.
 	if b {
-		for _, p := range pstructarr {
-			printintpointer(p.intp) // ERROR "live at call to printintpointer: .autotmp_[0-9]+ .autotmp_[0-9]+$"
+		for _, p := range pstructarr { // ERROR "stack object .autotmp_[0-9]+ \[10\]pstruct$"
+			printintpointer(p.intp) // ERROR "live at call to printintpointer: .autotmp_[0-9]+$"
 		}
 	}
-	for _, p := range pstructarr {
-		printintpointer(p.intp) // ERROR "live at call to printintpointer: .autotmp_[0-9]+ .autotmp_[0-9]+$"
+	for _, p := range pstructarr { // ERROR "stack object .autotmp_[0-9]+ \[10\]pstruct$"
+		printintpointer(p.intp) // ERROR "live at call to printintpointer: .autotmp_[0-9]+$"
 	}
-	for _, p := range pstructarr {
-		printintpointer(p.intp) // ERROR "live at call to printintpointer: .autotmp_[0-9]+ .autotmp_[0-9]+$"
+	for _, p := range pstructarr { // ERROR "stack object .autotmp_[0-9]+ \[10\]pstruct$"
+		printintpointer(p.intp) // ERROR "live at call to printintpointer: .autotmp_[0-9]+$"
 	}
 }
 
@@ -494,13 +493,13 @@ func f30(b bool) {
 
 func f31(b1, b2, b3 bool) {
 	if b1 {
-		g31(str()) // ERROR "live at call to convT2Estring: .autotmp_[0-9]+$" "live at call to g31: .autotmp_[0-9]+$"
+		g31(str()) // ERROR "stack object .autotmp_[0-9]+ string$"
 	}
 	if b2 {
-		h31(str()) // ERROR "live at call to convT2Estring: .autotmp_[0-9]+ .autotmp_[0-9]+$" "live at call to h31: .autotmp_[0-9]+$" "live at call to newobject: .autotmp_[0-9]+$"
+		h31(str()) // ERROR "live at call to convT2Estring: .autotmp_[0-9]+$" "live at call to newobject: .autotmp_[0-9]+$" "stack object .autotmp_[0-9]+ string$"
 	}
 	if b3 {
-		panic(str()) // ERROR "live at call to convT2Estring: .autotmp_[0-9]+$" "live at call to gopanic: .autotmp_[0-9]+$"
+		panic(str()) // ERROR "stack object .autotmp_[0-9]+ string$"
 	}
 	print(b3)
 }
@@ -520,10 +519,10 @@ var t32 T32
 
 func f32(b bool) {
 	if b {
-		call32(t32.Inc) // ERROR "live at call to call32: .autotmp_[0-9]+$"
+		call32(t32.Inc) // ERROR "stack object .autotmp_[0-9]+ struct \{"
 	}
-	call32(t32.Inc) // ERROR "live at call to call32: .autotmp_[0-9]+$"
-	call32(t32.Inc) // ERROR "live at call to call32: .autotmp_[0-9]+$"
+	call32(t32.Inc) // ERROR "stack object .autotmp_[0-9]+ struct \{"
+	call32(t32.Inc) // ERROR "stack object .autotmp_[0-9]+ struct \{"
 }
 
 //go:noescape
@@ -535,7 +534,7 @@ func call32(func())
 var m33 map[interface{}]int
 
 func f33() {
-	if m33[byteptr()] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+	if m33[byteptr()] == 0 { // ERROR "stack object .autotmp_[0-9]+ interface \{\}$"
 		printnl()
 		return
 	} else {
@@ -545,7 +544,7 @@ func f33() {
 }
 
 func f34() {
-	if m33[byteptr()] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+	if m33[byteptr()] == 0 { // ERROR "stack object .autotmp_[0-9]+ interface \{\}$"
 		printnl()
 		return
 	}
@@ -553,7 +552,8 @@ func f34() {
 }
 
 func f35() {
-	if m33[byteptr()] == 0 && m33[byteptr()] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$" "f35: .autotmp_[0-9]+ \(type interface \{\}\) is ambiguously live$"
+	if m33[byteptr()] == 0 && // ERROR "stack object .autotmp_[0-9]+ interface \{\}"
+		m33[byteptr()] == 0 { // ERROR "stack object .autotmp_[0-9]+ interface \{\}"
 		printnl()
 		return
 	}
@@ -561,7 +561,8 @@ func f35() {
 }
 
 func f36() {
-	if m33[byteptr()] == 0 || m33[byteptr()] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$" "f36: .autotmp_[0-9]+ \(type interface \{\}\) is ambiguously live$"
+	if m33[byteptr()] == 0 || // ERROR "stack object .autotmp_[0-9]+ interface \{\}"
+		m33[byteptr()] == 0 { // ERROR "stack object .autotmp_[0-9]+ interface \{\}"
 		printnl()
 		return
 	}
@@ -569,7 +570,9 @@ func f36() {
 }
 
 func f37() {
-	if (m33[byteptr()] == 0 || m33[byteptr()] == 0) && m33[byteptr()] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$" "f37: .autotmp_[0-9]+ \(type interface \{\}\) is ambiguously live$"
+	if (m33[byteptr()] == 0 || // ERROR "stack object .autotmp_[0-9]+ interface \{\}"
+		m33[byteptr()] == 0) && // ERROR "stack object .autotmp_[0-9]+ interface \{\}"
+		m33[byteptr()] == 0 { // ERROR "stack object .autotmp_[0-9]+ interface \{\}"
 		printnl()
 		return
 	}
@@ -589,14 +592,14 @@ func f38(b bool) {
 	// we care that the println lines have no live variables
 	// and therefore no output.
 	if b {
-		select { // ERROR "live at call to selectgo:( .autotmp_[0-9]+)+$"
+		select { // ERROR "live at call to selectgo:( .autotmp_[0-9]+)+$" "stack object .autotmp_[0-9]+ \[4\]struct \{"
 		case <-fc38():
 			printnl()
-		case fc38() <- *fi38(1): // ERROR "live at call to fc38:( .autotmp_[0-9]+)+$" "live at call to fi38:( .autotmp_[0-9]+)+$"
+		case fc38() <- *fi38(1): // ERROR "live at call to fc38:( .autotmp_[0-9]+)+$" "live at call to fi38:( .autotmp_[0-9]+)+$" "stack object .autotmp_[0-9]+ string$"
 			printnl()
-		case *fi38(2) = <-fc38(): // ERROR "live at call to fc38:( .autotmp_[0-9]+)+$" "live at call to fi38:( .autotmp_[0-9]+)+$"
+		case *fi38(2) = <-fc38(): // ERROR "live at call to fc38:( .autotmp_[0-9]+)+$" "live at call to fi38:( .autotmp_[0-9]+)+$" "stack object .autotmp_[0-9]+ string$"
 			printnl()
-		case *fi38(3), *fb38() = <-fc38(): // ERROR "live at call to fb38:( .autotmp_[0-9]+)+$" "live at call to fc38:( .autotmp_[0-9]+)+$" "live at call to fi38:( .autotmp_[0-9]+)+$"
+		case *fi38(3), *fb38() = <-fc38(): // ERROR "stack object .autotmp_[0-9]+ string$" "live at call to fc38:( .autotmp_[0-9]+)+$" "live at call to fi38:( .autotmp_[0-9]+)+$"
 			printnl()
 		}
 		printnl()
@@ -655,15 +658,17 @@ func bad40() {
 }
 
 func good40() {
-	ret := T40{}
-	ret.m = make(map[int]int) // ERROR "live at call to fastrand: .autotmp_[0-9]+ ret$"
+	ret := T40{}              // ERROR "stack object ret T40$"
+	ret.m = make(map[int]int) // ERROR "live at call to fastrand: .autotmp_[0-9]+ ret$" "stack object .autotmp_[0-9]+ map.hdr\[int\]int$"
 	t := &ret
-	printnl() // ERROR "live at call to printnl: .autotmp_[0-9]+ ret$"
-	useT40(t) // ERROR "live at call to useT40: .autotmp_[0-9]+ ret$"
+	printnl() // ERROR "live at call to printnl: ret$"
+	// Note: ret is live at the printnl because the compiler moves &ret
+	// from before the printnl to after.
+	useT40(t)
 }
 
 func ddd1(x, y *int) { // ERROR "live at entry to ddd1: x y$"
-	ddd2(x, y) // ERROR "live at call to ddd2: .autotmp_[0-9]+$"
+	ddd2(x, y) // ERROR "stack object .autotmp_[0-9]+ \[2\]\*int$"
 	printnl()
 	// Note: no .?autotmp live at printnl.  See issue 16996.
 }
diff --git a/test/live2.go b/test/live2.go
index cc1b0b7acf..cea312f075 100644
--- a/test/live2.go
+++ b/test/live2.go
@@ -10,7 +10,6 @@
 package main
 
 // issue 8142: lost 'addrtaken' bit on inlined variables.
-// no inlining in this test, so just checking that non-inlined works.
 
 func printnl()
 
@@ -28,15 +27,15 @@ func newT40() *T40 {
 }
 
 func bad40() {
-	t := newT40() // ERROR "live at call to makemap: .autotmp_[0-9]+ ret$"
-	printnl()     // ERROR "live at call to printnl: .autotmp_[0-9]+ ret$"
-	useT40(t)     // ERROR "live at call to useT40: .autotmp_[0-9]+ ret$"
+	t := newT40() // ERROR "live at call to makemap: ret$" "stack object ret T40$" "stack object .autotmp_[0-9]+ map.hdr\[int\]int$"
+	printnl()     // ERROR "live at call to printnl: ret$"
+	useT40(t)
 }
 
 func good40() {
-	ret := T40{}
-	ret.m = make(map[int]int, 42) // ERROR "live at call to makemap: .autotmp_[0-9]+ ret$"
+	ret := T40{}                  // ERROR "stack object ret T40$"
+	ret.m = make(map[int]int, 42) // ERROR "live at call to makemap: ret$" "stack object .autotmp_[0-9]+ map.hdr\[int\]int$"
 	t := &ret
-	printnl() // ERROR "live at call to printnl: .autotmp_[0-9]+ ret$"
-	useT40(t) // ERROR "live at call to useT40: .autotmp_[0-9]+ ret$"
+	printnl() // ERROR "live at call to printnl: ret$"
+	useT40(t)
 }
diff --git a/test/live_syscall.go b/test/live_syscall.go
index 65a161c028..b7b85bcabf 100644
--- a/test/live_syscall.go
+++ b/test/live_syscall.go
@@ -19,22 +19,22 @@ func f(uintptr) // ERROR "f assuming arg#1 is unsafe uintptr"
 
 func g() {
 	var t int
-	f(uintptr(unsafe.Pointer(&t))) // ERROR "live at call to f: .?autotmp" "g &t does not escape"
+	f(uintptr(unsafe.Pointer(&t))) // ERROR "live at call to f: .?autotmp" "g &t does not escape" "stack object .autotmp_[0-9]+ unsafe.Pointer$"
 }
 
 func h() {
 	var v int
-	syscall.Syscall(0, 1, uintptr(unsafe.Pointer(&v)), 2) // ERROR "live at call to Syscall: .?autotmp" "h &v does not escape"
+	syscall.Syscall(0, 1, uintptr(unsafe.Pointer(&v)), 2) // ERROR "live at call to Syscall: .?autotmp" "h &v does not escape" "stack object .autotmp_[0-9]+ unsafe.Pointer$"
 }
 
 func i() {
 	var t int
 	p := unsafe.Pointer(&t) // ERROR "i &t does not escape"
-	f(uintptr(p))           // ERROR "live at call to f: .?autotmp"
+	f(uintptr(p))           // ERROR "live at call to f: .?autotmp" "stack object .autotmp_[0-9]+ unsafe.Pointer$"
 }
 
 func j() {
 	var v int
 	p := unsafe.Pointer(&v)              // ERROR "j &v does not escape"
-	syscall.Syscall(0, 1, uintptr(p), 2) // ERROR "live at call to Syscall: .?autotmp"
+	syscall.Syscall(0, 1, uintptr(p), 2) // ERROR "live at call to Syscall: .?autotmp" "stack object .autotmp_[0-9]+ unsafe.Pointer$"
 }
diff --git a/test/stackobj.go b/test/stackobj.go
new file mode 100644
index 0000000000..b6af4bd8f3
--- /dev/null
+++ b/test/stackobj.go
@@ -0,0 +1,57 @@
+// run
+
+// Copyright 2018 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 main
+
+import (
+	"fmt"
+	"runtime"
+)
+
+type HeapObj [8]int64
+
+type StkObj struct {
+	h *HeapObj
+}
+
+var n int
+var c int = -1
+
+func gc() {
+	// encourage heap object to be collected, and have its finalizer run.
+	runtime.GC()
+	runtime.GC()
+	runtime.GC()
+	n++
+}
+
+func main() {
+	f()
+	gc() // prior to stack objects, heap object is not collected until here
+	if c < 0 {
+		panic("heap object never collected")
+	}
+	if c != 1 {
+		panic(fmt.Sprintf("expected collection at phase 1, got phase %d", c))
+	}
+}
+
+func f() {
+	var s StkObj
+	s.h = new(HeapObj)
+	runtime.SetFinalizer(s.h, func(h *HeapObj) {
+		// Remember at what phase the heap object was collected.
+		c = n
+	})
+	g(&s)
+	gc()
+}
+
+func g(s *StkObj) {
+	gc() // heap object is still live here
+	runtime.KeepAlive(s)
+	gc() // heap object should be collected here
+}
diff --git a/test/stackobj3.go b/test/stackobj3.go
new file mode 100644
index 0000000000..8bb8fb3270
--- /dev/null
+++ b/test/stackobj3.go
@@ -0,0 +1,93 @@
+// run
+
+// Copyright 2018 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.
+
+// This test makes sure that ambiguously live arguments work correctly.
+
+package main
+
+import (
+	"runtime"
+)
+
+type HeapObj [8]int64
+
+type StkObj struct {
+	h *HeapObj
+}
+
+var n int
+var c int = -1
+
+func gc() {
+	// encourage heap object to be collected, and have its finalizer run.
+	runtime.GC()
+	runtime.GC()
+	runtime.GC()
+	n++
+}
+
+var null StkObj
+
+var sink *HeapObj
+
+//go:noinline
+func use(p *StkObj) {
+}
+
+//go:noinline
+func f(s StkObj, b bool) {
+	var p *StkObj
+	if b {
+		p = &s
+	} else {
+		p = &null
+	}
+	// use is required here to prevent the conditional
+	// code above from being executed after the first gc() call.
+	use(p)
+	// If b==false, h should be collected here.
+	gc() // 0
+	sink = p.h
+	gc() // 1
+	sink = nil
+	// If b==true, h should be collected here.
+	gc() // 2
+}
+
+func fTrue() {
+	var s StkObj
+	s.h = new(HeapObj)
+	c = -1
+	n = 0
+	runtime.SetFinalizer(s.h, func(h *HeapObj) {
+		// Remember at what phase the heap object was collected.
+		c = n
+	})
+	f(s, true)
+	if c != 2 {
+		panic("bad liveness")
+	}
+}
+
+func fFalse() {
+	var s StkObj
+	s.h = new(HeapObj)
+	c = -1
+	n = 0
+	runtime.SetFinalizer(s.h, func(h *HeapObj) {
+		// Remember at what phase the heap object was collected.
+		c = n
+	})
+	f(s, false)
+	if c != 0 {
+		panic("bad liveness")
+	}
+}
+
+func main() {
+	fTrue()
+	fFalse()
+}
diff --git a/test/uintptrescapes2.go b/test/uintptrescapes2.go
index c94bc148c8..e7b5d721f5 100644
--- a/test/uintptrescapes2.go
+++ b/test/uintptrescapes2.go
@@ -30,14 +30,14 @@ func F4(...uintptr) {} // ERROR "escaping ...uintptr"
 
 func G() {
 	var t int                        // ERROR "moved to heap"
-	F1(uintptr(unsafe.Pointer(&t)))  // ERROR "live at call to F1: .?autotmp" "&t escapes to heap"
+	F1(uintptr(unsafe.Pointer(&t)))  // ERROR "live at call to F1: .?autotmp" "&t escapes to heap" "stack object .autotmp_[0-9]+ unsafe.Pointer$"
 	var t2 int                       // ERROR "moved to heap"
-	F3(uintptr(unsafe.Pointer(&t2))) // ERROR "live at call to F3: .?autotmp" "&t2 escapes to heap"
+	F3(uintptr(unsafe.Pointer(&t2))) // ERROR "live at call to F3: .?autotmp" "&t2 escapes to heap" "stack object .autotmp_[0-9]+ unsafe.Pointer$"
 }
 
 func H() {
 	var v int                                 // ERROR "moved to heap"
-	F2(0, 1, uintptr(unsafe.Pointer(&v)), 2)  // ERROR "live at call to newobject: .?autotmp" "live at call to F2: .?autotmp" "escapes to heap"
+	F2(0, 1, uintptr(unsafe.Pointer(&v)), 2)  // ERROR "live at call to newobject: .?autotmp" "live at call to F2: .?autotmp" "escapes to heap" "stack object .autotmp_[0-9]+ unsafe.Pointer$"
 	var v2 int                                // ERROR "moved to heap"
-	F4(0, 1, uintptr(unsafe.Pointer(&v2)), 2) // ERROR "live at call to newobject: .?autotmp" "live at call to F4: .?autotmp" "escapes to heap"
+	F4(0, 1, uintptr(unsafe.Pointer(&v2)), 2) // ERROR "live at call to newobject: .?autotmp" "live at call to F4: .?autotmp" "escapes to heap" "stack object .autotmp_[0-9]+ unsafe.Pointer$"
 }