cmd/compile/loopvar: adjust logging messages

Michael Stapelberg thought the former messages had
upside potential, Russ and I agreed.

Also slightly tweaked the json logging, not sure if
anyone will use it but it should at least be okay.

Change-Id: Iaab75114dd5f5d8f011fab22d32b57abc0272815
Reviewed-on: https://go-review.googlesource.com/c/go/+/493135
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: David Chase <drchase@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Michael Stapelberg <stapelberg@google.com>

2 files changed, 20 insertions, 14 deletions

diff --git a/src/cmd/compile/internal/loopvar/loopvar.go b/src/cmd/compile/internal/loopvar/loopvar.go
index 44ff449689..0d8a6d2d6e 100644
--- a/src/cmd/compile/internal/loopvar/loopvar.go
+++ b/src/cmd/compile/internal/loopvar/loopvar.go
@@ -545,29 +545,35 @@ func LogTransformations(transformed []VarAndLoop) {
 				loops = append(loops, loopPos{l, lv.LastPos, n.Curfn})
 			}
 			pos := n.Pos()
+
+			inner := base.Ctxt.InnermostPos(pos)
+			outer := base.Ctxt.OutermostPos(pos)
+
 			if logopt.Enabled() {
 				// For automated checking of coverage of this transformation, include this in the JSON information.
+				var nString interface{} = n
+				if inner != outer {
+					nString = fmt.Sprintf("%v (from inline)", n)
+				}
 				if n.Esc() == ir.EscHeap {
-					logopt.LogOpt(pos, "transform-escape", "loopvar", ir.FuncName(n.Curfn))
+					logopt.LogOpt(pos, "iteration-variable-to-heap", "loopvar", ir.FuncName(n.Curfn), nString)
 				} else {
-					logopt.LogOpt(pos, "transform-noescape", "loopvar", ir.FuncName(n.Curfn))
+					logopt.LogOpt(pos, "iteration-variable-to-stack", "loopvar", ir.FuncName(n.Curfn), nString)
 				}
 			}
 			if print {
-				inner := base.Ctxt.InnermostPos(pos)
-				outer := base.Ctxt.OutermostPos(pos)
 				if inner == outer {
 					if n.Esc() == ir.EscHeap {
-						base.WarnfAt(pos, "transformed loop variable %v escapes", n)
+						base.WarnfAt(pos, "loop variable %v now per-iteration, heap-allocated", n)
 					} else {
-						base.WarnfAt(pos, "transformed loop variable %v does not escape", n)
+						base.WarnfAt(pos, "loop variable %v now per-iteration, stack-allocated", n)
 					}
 				} else {
 					innerXPos := trueInlinedPos(inner)
 					if n.Esc() == ir.EscHeap {
-						base.WarnfAt(innerXPos, "transformed loop variable %v escapes (loop inlined into %s:%d)", n, outer.Filename(), outer.Line())
+						base.WarnfAt(innerXPos, "loop variable %v now per-iteration, heap-allocated (loop inlined into %s:%d)", n, outer.Filename(), outer.Line())
 					} else {
-						base.WarnfAt(innerXPos, "transformed loop variable %v does not escape (loop inlined into %s:%d)", n, outer.Filename(), outer.Line())
+						base.WarnfAt(innerXPos, "loop variable %v now per-iteration, stack-allocated (loop inlined into %s:%d)", n, outer.Filename(), outer.Line())
 					}
 				}
 			}
@@ -577,18 +583,18 @@ func LogTransformations(transformed []VarAndLoop) {
 			last := l.last
 			if logopt.Enabled() {
 				// Intended to
-				logopt.LogOptRange(pos, last, "transform-loop", "loopvar", ir.FuncName(l.curfn))
+				logopt.LogOptRange(pos, last, "loop-modified", "loopvar", ir.FuncName(l.curfn))
 			}
 			if print && 3 <= base.Debug.LoopVar {
 				// TODO decide if we want to keep this, or not.  It was helpful for validating logopt, otherwise, eh.
 				inner := base.Ctxt.InnermostPos(pos)
 				outer := base.Ctxt.OutermostPos(pos)
 				if inner == outer {
-					base.WarnfAt(pos, "loop ending at %d:%d was transformed", last.Line(), last.Col())
+					base.WarnfAt(pos, "loop ending at %d:%d was modified", last.Line(), last.Col())
 				} else {
 					pos = trueInlinedPos(inner)
 					last = trueInlinedPos(base.Ctxt.InnermostPos(last))
-					base.WarnfAt(pos, "loop ending at %d:%d was transformed (loop inlined into %s:%d)", last.Line(), last.Col(), outer.Filename(), outer.Line())
+					base.WarnfAt(pos, "loop ending at %d:%d was modified (loop inlined into %s:%d)", last.Line(), last.Col(), outer.Filename(), outer.Line())
 				}
 			}
 		}
diff --git a/src/cmd/compile/internal/loopvar/loopvar_test.go b/src/cmd/compile/internal/loopvar/loopvar_test.go
index 22ff15ee8b..1a13f0e30c 100644
--- a/src/cmd/compile/internal/loopvar/loopvar_test.go
+++ b/src/cmd/compile/internal/loopvar/loopvar_test.go
@@ -39,12 +39,12 @@ var cases = []testcase{
 	{"-1", "", 11, for_files[:1]},
 	{"0", "", 0, for_files[:1]},
 	{"1", "", 0, for_files[:1]},
-	{"2", "transformed loop variable i ", 0, for_files},
+	{"2", "loop variable i now per-iteration,", 0, for_files},
 
 	{"-1", "", 11, range_files[:1]},
 	{"0", "", 0, range_files[:1]},
 	{"1", "", 0, range_files[:1]},
-	{"2", "transformed loop variable i ", 0, range_files},
+	{"2", "loop variable i now per-iteration,", 0, range_files},
 
 	{"1", "", 0, []string{"for_nested.go"}},
 }
@@ -230,7 +230,7 @@ func TestLoopVarOpt(t *testing.T) {
 
 	t.Logf(m)
 
-	yCount := strings.Count(m, "opt.go:16:6: transformed loop variable private escapes (loop inlined into ./opt.go:30)")
+	yCount := strings.Count(m, "opt.go:16:6: loop variable private now per-iteration, heap-allocated (loop inlined into ./opt.go:30)")
 	nCount := strings.Count(m, "shared")
 
 	if yCount != 1 {