cmd/gc: distinguish unnamed vs blank-named return variables better

Before, an unnamed return value turned into an ONAME node n with n->sym
named ~anon%d, and n->orig == n.

A blank-named return value turned into an ONAME node n with n->sym
named ~anon%d but n->orig == the original blank n. Code generation and
printing uses n->orig, so that this node formatted as _.

But some code does not use n->orig. In particular the liveness code does
not know about the n->orig convention and so mishandles blank identifiers.
It is possible to fix but seemed better to avoid the confusion entirely.

Now the first kind of node is named ~r%d and the second ~b%d; both have
n->orig == n, so that it doesn't matter whether code uses n or n->orig.

After this change the ->orig field is only used for other kinds of expressions,
not for ONAME nodes.

This requires distinguishing ~b from ~r names in a few places that care.
It fixes a liveness analysis bug without actually changing the liveness code.

TBR=ken2
CC=golang-codereviews
https://codereview.appspot.com/63630043

1 files changed, 4 insertions, 4 deletions

diff --git a/test/escape5.go b/test/escape5.go
index c9646872d..a33daeee1 100644
--- a/test/escape5.go
+++ b/test/escape5.go
@@ -17,19 +17,19 @@ func leaktoret(p *int) *int { // ERROR "leaking param: p to result"
 	return p
 }
 
-func leaktoret2(p *int) (*int, *int) { // ERROR "leaking param: p to result .anon1" "leaking param: p to result .anon2"
+func leaktoret2(p *int) (*int, *int) { // ERROR "leaking param: p to result ~r1" "leaking param: p to result ~r2"
 	return p, p
 }
 
-func leaktoret22(p, q *int) (*int, *int) { // ERROR "leaking param: p to result .anon2" "leaking param: q to result .anon3"
+func leaktoret22(p, q *int) (*int, *int) { // ERROR "leaking param: p to result ~r2" "leaking param: q to result ~r3"
 	return p, q
 }
 
-func leaktoret22b(p, q *int) (*int, *int) { // ERROR "leaking param: p to result .anon3" "leaking param: q to result .anon2"
+func leaktoret22b(p, q *int) (*int, *int) { // ERROR "leaking param: p to result ~r3" "leaking param: q to result ~r2"
 	return leaktoret22(q, p)
 }
 
-func leaktoret22c(p, q *int) (*int, *int) { // ERROR "leaking param: p to result .anon3" "leaking param: q to result .anon2"
+func leaktoret22c(p, q *int) (*int, *int) { // ERROR "leaking param: p to result ~r3" "leaking param: q to result ~r2"
 	r, s := leaktoret22(q, p)
 	return r, s
 }