cmd/compile: generate late-lowering static calls

This is testing for the limited case of zero or one SSA-able results.

One regression is that the later expansion of "Dereference" into
Move into argument slots thwarts the
  MOVE A -> B, MOVE B -> C
replaced-by
  MOVE A -> B, MOVE A -> C
optimization; the second move is written instead as a Dereference at the
phase where the optimization occurs, and because the target of the
dereference is not visible in the dereference, it's not possible to verify
that A and B or A and C don't overlap in some peculiar way (and for results
fed to args, they can).

Regression is repaired in a later CL by changing when calls are expanded.

Change-Id: Ia0f48a9d483d5a54a99657a24b12b25b8edde55f
Reviewed-on: https://go-review.googlesource.com/c/go/+/242782
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/cmd/compile/internal/types/type.go b/src/cmd/compile/internal/types/type.go
index 9b05aef429..5d1d5d4008 100644
--- a/src/cmd/compile/internal/types/type.go
+++ b/src/cmd/compile/internal/types/type.go
@@ -68,7 +68,7 @@ const (
 	// SSA backend types
 	TSSA     // internal types used by SSA backend (flags, memory, etc.)
 	TTUPLE   // a pair of types, used by SSA backend
-	TRESULTS // multiuple types; the resulting of calling a function or method, plus a memory at the end.
+	TRESULTS // multiple types; the result of calling a function or method, with a memory at the end.
 
 	NTYPE
 )
@@ -331,9 +331,9 @@ type Tuple struct {
 	// Any tuple with a memory type must put that memory type second.
 }
 
+// Results are the output from calls that will be late-expanded.
 type Results struct {
-	Types []*Type
-	// Any Results with a memory type must put that memory type last.
+	Types []*Type // Last element is memory output from call.
 }
 
 // Array contains Type fields specific to array types.