cmd/compile: add explicit 'where' to EscStep data for explanations

Sometimes neither the src nor the dst of an escape edge
contains the line number appropriate to the edge, so add
a field so that can be set correctly.

Also updated some of the explanations to be less jargon-y
and perhaps more informative, and folded bug example into
test.

Cleaned up some of the function/method names in esc.go
and did a quick sanity check that each "bundling" function
was actually called often enough to justify its existence.

Fixes #17459.

Change-Id: Ieba53ab0a6ba1f7a6c4962bc0b702ede9cc3a3cc
Reviewed-on: https://go-review.googlesource.com/31660
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

test/escape_because.go

@@ -30,22 +30,22 @@ func (p *pair) EqualParts() bool { // ERROR "\(\*pair\).EqualParts p does not es
 	return p != nil && (p.x == p.y || *p.x == *p.y)
 }
 
-func f1(p *int) { // ERROR "from \[3\]\*int literal \(array literal element\) at escape_because.go:34$" "from a \(assigned\) at escape_because.go:34$" "from a \(interface-converted\) at escape_because.go:35$" "from sink \(assigned to top level variable\) at escape_because.go:19$" "leaking param: p$"
+func f1(p *int) { // ERROR "from \[3\]\*int literal \(array literal element\) at escape_because.go:34$" "from a \(assigned\) at escape_because.go:34$" "from a \(interface-converted\) at escape_because.go:35$" "from sink \(assigned to top level variable\) at escape_because.go:35$" "leaking param: p$"
 	a := [3]*int{p, nil, nil}
-	sink = a // ERROR "a escapes to heap$" "from sink \(assigned to top level variable\) at escape_because.go:19$"
+	sink = a // ERROR "a escapes to heap$" "from sink \(assigned to top level variable\) at escape_because.go:35$"
 
 }
 
-func f2(q *int) { // ERROR "from &u \(address-of\) at escape_because.go:43$" "from &u \(interface-converted\) at escape_because.go:43$" "from pair literal \(struct literal element\) at escape_because.go:41$" "from s \(assigned\) at escape_because.go:40$" "from sink \(assigned to top level variable\) at escape_because.go:19$" "from t \(assigned\) at escape_because.go:41$" "from u \(assigned\) at escape_because.go:42$" "leaking param: q$"
+func f2(q *int) { // ERROR "from &u \(address-of\) at escape_because.go:43$" "from &u \(interface-converted\) at escape_because.go:43$" "from pair literal \(struct literal element\) at escape_because.go:41$" "from s \(assigned\) at escape_because.go:40$" "from sink \(assigned to top level variable\) at escape_because.go:43$" "from t \(assigned\) at escape_because.go:41$" "from u \(assigned\) at escape_because.go:42$" "leaking param: q$"
 	s := q
 	t := pair{s, nil}
 	u := t    // ERROR "moved to heap: u$"
-	sink = &u // ERROR "&u escapes to heap$" "from &u \(interface-converted\) at escape_because.go:43$" "from sink \(assigned to top level variable\) at escape_because.go:19$"
+	sink = &u // ERROR "&u escapes to heap$" "from &u \(interface-converted\) at escape_because.go:43$" "from sink \(assigned to top level variable\) at escape_because.go:43$"
 }
 
-func f3(r *int) interface{} { // ERROR "from \[\]\*int literal \(slice-literal-element\) at escape_because.go:47$" "from c \(assigned\) at escape_because.go:47$" "from c \(interface-converted\) at escape_because.go:48$" "from ~r1 \(return\) at escape_because.go:46$" "leaking param: r to result ~r1 level=-1$"
-	c := []*int{r} // ERROR "\[\]\*int literal escapes to heap$" "from c \(assigned\) at escape_because.go:47$" "from c \(interface-converted\) at escape_because.go:48$" "from ~r1 \(return\) at escape_because.go:46$"
-	return c       // "return" // ERROR "c escapes to heap$" "from ~r1 \(return\) at escape_because.go:46$"
+func f3(r *int) interface{} { // ERROR "from \[\]\*int literal \(slice-literal-element\) at escape_because.go:47$" "from c \(assigned\) at escape_because.go:47$" "from c \(interface-converted\) at escape_because.go:48$" "from ~r1 \(return\) at escape_because.go:48$" "leaking param: r to result ~r1 level=-1$"
+	c := []*int{r} // ERROR "\[\]\*int literal escapes to heap$" "from c \(assigned\) at escape_because.go:47$" "from c \(interface-converted\) at escape_because.go:48$" "from ~r1 \(return\) at escape_because.go:48$"
+	return c       // "return" // ERROR "c escapes to heap$" "from ~r1 \(return\) at escape_because.go:48$"
 }
 
 func f4(a *int, s []*int) int { // ERROR "from \*s \(indirection\) at escape_because.go:51$" "from append\(s, a\) \(appended to slice\) at escape_because.go:52$" "from append\(s, a\) \(appendee slice\) at escape_because.go:52$" "leaking param content: s$" "leaking param: a$"
@@ -73,15 +73,15 @@ func f7(x map[int]*int, y int) *int { // ERROR "f7 x does not escape$"
 	return z
 }
 
-func f8(x int, y *int) *int { // ERROR "from ~r2 \(return\) at escape_because.go:76$" "from ~r2 \(returned from recursive function\) at escape_because.go:76$" "leaking param: y$" "moved to heap: x$"
+func f8(x int, y *int) *int { // ERROR "from ~r2 \(return\) at escape_because.go:78$" "from ~r2 \(returned from recursive function\) at escape_because.go:76$" "leaking param: y$" "moved to heap: x$"
 	if x <= 0 {
 		return y
 	}
 	x--
-	return f8(*y, &x) // ERROR "&x escapes to heap$" "from y \(arg to recursive call\) at escape_because.go:76$" "from ~r2 \(return\) at escape_because.go:76$" "from ~r2 \(returned from recursive function\) at escape_because.go:76$"
+	return f8(*y, &x) // ERROR "&x escapes to heap$" "from y \(arg to recursive call\) at escape_because.go:81$" "from ~r2 \(return\) at escape_because.go:78$" "from ~r2 \(returned from recursive function\) at escape_because.go:76$"
 }
 
-func f9(x int, y ...*int) *int { // ERROR "from y\[0\] \(dot of pointer\) at escape_because.go:86$" "from ~r2 \(return\) at escape_because.go:84$" "from ~r2 \(returned from recursive function\) at escape_because.go:84$" "leaking param content: y$" "leaking param: y to result ~r2 level=1$" "moved to heap: x$"
+func f9(x int, y ...*int) *int { // ERROR "from y\[0\] \(dot of pointer\) at escape_because.go:86$" "from ~r2 \(return\) at escape_because.go:86$" "from ~r2 \(returned from recursive function\) at escape_because.go:84$" "leaking param content: y$" "leaking param: y to result ~r2 level=1$" "moved to heap: x$"
 	if x <= 0 {
 		return y[0]
 	}
@@ -95,7 +95,27 @@ func f10(x map[*int]*int, y, z *int) *int { // ERROR "f10 x does not escape$" "f
 }
 
 func f11(x map[*int]*int, y, z *int) map[*int]*int { // ERROR "f11 x does not escape$" "from map\[\*int\]\*int literal \(map literal key\) at escape_because.go:98$" "from map\[\*int\]\*int literal \(map literal value\) at escape_because.go:98$" "leaking param: y$" "leaking param: z$"
-	return map[*int]*int{y: z} // ERROR "from ~r3 \(return\) at escape_because.go:97$" "map\[\*int\]\*int literal escapes to heap$"
+	return map[*int]*int{y: z} // ERROR "from ~r3 \(return\) at escape_because.go:98$" "map\[\*int\]\*int literal escapes to heap$"
+}
+
+func f12() {
+	b := []byte("test") // ERROR "\(\[\]byte\)\(.test.\) escapes to heap$" "from b \(assigned\) at escape_because.go:102$" "from b \(passed to call\[argument escapes\]\) at escape_because.go:103$"
+	escape(b)
+}
+
+func escape(b []byte) { // ERROR "from panic\(b\) \(panic\) at escape_because.go:107$" "leaking param: b$"
+	panic(b)
+}
+
+func f13() {
+	b := []byte("test") // ERROR "\(\[\]byte\)\(.test.\) escapes to heap$" "from .out0 \(passed-to-and-returned-from-call\) at escape_because.go:112$" "from b \(assigned\) at escape_because.go:111$" "from c \(assigned\) at escape_because.go:112$" "from c \(passed to call\[argument escapes\]\) at escape_because.go:113$"
+	c := transmit(b)
+	escape(c)
+}
+
+//go:noinline
+func transmit(b []byte) []byte { // ERROR "from ~r1 \(return\) at escape_because.go:118$" "leaking param: b to result ~r1 level=0$"
+	return b
 }
 
 // The list below is all of the why-escapes messages seen building the escape analysis tests.
@@ -142,9 +162,9 @@ key of map put
 map literal key
 map literal value
 parameter to indirect call
-passed to function[content escapes]
-passed to function[unknown]
-passed-to-and-returned-from-function
+passed to call[argument content escapes]
+passed to call[argument escapes]
+passed-to-and-returned-from-call
 pointer literal
 range
 range-deref