[dev.typeparams] cmd/compile: simplify ~r/~b naming

The compiler renames anonymous and blank result parameters to ~rN or
~bN, but the current semantics for computing N are rather annoying and
difficult to reproduce cleanly. They also lead to difficult to read
escape analysis results in tests.

This CL changes N to always be calculated as the parameter's index
within the function's result parameter tuple. E.g., if a function has
a single result, it will now always be named "~r0".

The normative change to this CL is fairly simple, but it requires
updating a lot of test expectations.

Change-Id: I58a3c94de00cb822cb94efe52d115531193c993c
Reviewed-on: https://go-review.googlesource.com/c/go/+/323010
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/test/escape_slice.go b/test/escape_slice.go
index d60414736c..055b60be41 100644
--- a/test/escape_slice.go
+++ b/test/escape_slice.go
@@ -101,7 +101,7 @@ func slice11() {
 	_ = s
 }
 
-func slice12(x []int) *[1]int { // ERROR "leaking param: x to result ~r1 level=0$"
+func slice12(x []int) *[1]int { // ERROR "leaking param: x to result ~r0 level=0$"
 	return (*[1]int)(x)
 }
 
@@ -110,7 +110,7 @@ func envForDir(dir string) []string { // ERROR "dir does not escape"
 	return mergeEnvLists([]string{"PWD=" + dir}, env) // ERROR ".PWD=. \+ dir escapes to heap" "\[\]string{...} does not escape"
 }
 
-func mergeEnvLists(in, out []string) []string { // ERROR "leaking param content: in" "leaking param content: out" "leaking param: out to result ~r2 level=0"
+func mergeEnvLists(in, out []string) []string { // ERROR "leaking param content: in" "leaking param content: out" "leaking param: out to result ~r0 level=0"
 NextVar:
 	for _, inkv := range in {
 		k := strings.SplitAfterN(inkv, "=", 2)[0]