cmd/compile/internal/gc: unify self-assignment checks in esc.go

Move slice self-assign check into isSelfAssign function.
Make debug output consistent for all self-assignment cases.

Change-Id: I0e4cc7b3c1fcaeace7226dd80a0dc1ea97347a55
Reviewed-on: https://go-review.googlesource.com/136276
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
diff --git a/src/cmd/compile/internal/gc/esc.go b/src/cmd/compile/internal/gc/esc.go
index ad4d118..145007f 100644
--- a/src/cmd/compile/internal/gc/esc.go
+++ b/src/cmd/compile/internal/gc/esc.go
@@ -705,6 +705,10 @@
 // isSelfAssign reports whether assignment from src to dst can
 // be ignored by the escape analysis as it's effectively a self-assignment.
 func (e *EscState) isSelfAssign(dst, src *Node) bool {
+	if e.isSliceSelfAssign(dst, src) {
+		return true
+	}
+
 	// Detect trivial assignments that assign back to the same object.
 	//
 	// It covers these cases:
@@ -890,13 +894,6 @@
 
 	case OAS, OASOP:
 		// Filter out some no-op assignments for escape analysis.
-		if e.isSliceSelfAssign(n.Left, n.Right) {
-			if Debug['m'] != 0 {
-				Warnl(n.Pos, "%v ignoring self-assignment to %S", e.curfnSym(n), n.Left)
-			}
-
-			break
-		}
 		if e.isSelfAssign(n.Left, n.Right) {
 			if Debug['m'] != 0 {
 				Warnl(n.Pos, "%v ignoring self-assignment in %S", e.curfnSym(n), n)
diff --git a/test/escape2.go b/test/escape2.go
index 5c4c803..a39291e 100644
--- a/test/escape2.go
+++ b/test/escape2.go
@@ -1602,10 +1602,10 @@
 }
 
 func (b *Buffer) foo() { // ERROR "\(\*Buffer\).foo b does not escape$"
-	b.buf1 = b.buf1[1:2]   // ERROR "\(\*Buffer\).foo ignoring self-assignment to b.buf1$"
-	b.buf1 = b.buf1[1:2:3] // ERROR "\(\*Buffer\).foo ignoring self-assignment to b.buf1$"
-	b.buf1 = b.buf2[1:2]   // ERROR "\(\*Buffer\).foo ignoring self-assignment to b.buf1$"
-	b.buf1 = b.buf2[1:2:3] // ERROR "\(\*Buffer\).foo ignoring self-assignment to b.buf1$"
+	b.buf1 = b.buf1[1:2]   // ERROR "\(\*Buffer\).foo ignoring self-assignment in b.buf1 = b.buf1\[1:2\]$"
+	b.buf1 = b.buf1[1:2:3] // ERROR "\(\*Buffer\).foo ignoring self-assignment in b.buf1 = b.buf1\[1:2:3\]$"
+	b.buf1 = b.buf2[1:2]   // ERROR "\(\*Buffer\).foo ignoring self-assignment in b.buf1 = b.buf2\[1:2\]$"
+	b.buf1 = b.buf2[1:2:3] // ERROR "\(\*Buffer\).foo ignoring self-assignment in b.buf1 = b.buf2\[1:2:3\]$"
 }
 
 func (b *Buffer) bar() { // ERROR "leaking param: b$"
@@ -1613,13 +1613,13 @@
 }
 
 func (b *Buffer) arrayPtr() { // ERROR "\(\*Buffer\).arrayPtr b does not escape"
-	b.buf1 = b.arrPtr[1:2]   // ERROR "\(\*Buffer\).arrayPtr ignoring self-assignment to b.buf1"
-	b.buf1 = b.arrPtr[1:2:3] // ERROR "\(\*Buffer\).arrayPtr ignoring self-assignment to b.buf1"
+	b.buf1 = b.arrPtr[1:2]   // ERROR "\(\*Buffer\).arrayPtr ignoring self-assignment in b.buf1 = b.arrPtr\[1:2\]$"
+	b.buf1 = b.arrPtr[1:2:3] // ERROR "\(\*Buffer\).arrayPtr ignoring self-assignment in b.buf1 = b.arrPtr\[1:2:3\]$"
 }
 
 func (b *Buffer) baz() { // ERROR "\(\*Buffer\).baz b does not escape$"
-	b.str1 = b.str1[1:2] // ERROR "\(\*Buffer\).baz ignoring self-assignment to b.str1$"
-	b.str1 = b.str2[1:2] // ERROR "\(\*Buffer\).baz ignoring self-assignment to b.str1$"
+	b.str1 = b.str1[1:2] // ERROR "\(\*Buffer\).baz ignoring self-assignment in b.str1 = b.str1\[1:2\]$"
+	b.str1 = b.str2[1:2] // ERROR "\(\*Buffer\).baz ignoring self-assignment in b.str1 = b.str2\[1:2\]$"
 }
 
 func (b *Buffer) bat() { // ERROR "leaking param content: b$"
@@ -1629,8 +1629,8 @@
 }
 
 func quux(sp *string, bp *[]byte) { // ERROR "quux bp does not escape$" "quux sp does not escape$"
-	*sp = (*sp)[1:2] // ERROR "quux ignoring self-assignment to \*sp$"
-	*bp = (*bp)[1:2] // ERROR "quux ignoring self-assignment to \*bp$"
+	*sp = (*sp)[1:2] // ERROR "quux ignoring self-assignment in \*sp = \(\*sp\)\[1:2\]$"
+	*bp = (*bp)[1:2] // ERROR "quux ignoring self-assignment in \*bp = \(\*bp\)\[1:2\]$"
 }
 
 type StructWithString struct {
diff --git a/test/escape2n.go b/test/escape2n.go
index 4b1ca1e..989cf18 100644
--- a/test/escape2n.go
+++ b/test/escape2n.go
@@ -1602,10 +1602,10 @@
 }
 
 func (b *Buffer) foo() { // ERROR "\(\*Buffer\).foo b does not escape$"
-	b.buf1 = b.buf1[1:2]   // ERROR "\(\*Buffer\).foo ignoring self-assignment to b.buf1$"
-	b.buf1 = b.buf1[1:2:3] // ERROR "\(\*Buffer\).foo ignoring self-assignment to b.buf1$"
-	b.buf1 = b.buf2[1:2]   // ERROR "\(\*Buffer\).foo ignoring self-assignment to b.buf1$"
-	b.buf1 = b.buf2[1:2:3] // ERROR "\(\*Buffer\).foo ignoring self-assignment to b.buf1$"
+	b.buf1 = b.buf1[1:2]   // ERROR "\(\*Buffer\).foo ignoring self-assignment in b.buf1 = b.buf1\[1:2\]$"
+	b.buf1 = b.buf1[1:2:3] // ERROR "\(\*Buffer\).foo ignoring self-assignment in b.buf1 = b.buf1\[1:2:3\]$"
+	b.buf1 = b.buf2[1:2]   // ERROR "\(\*Buffer\).foo ignoring self-assignment in b.buf1 = b.buf2\[1:2\]$"
+	b.buf1 = b.buf2[1:2:3] // ERROR "\(\*Buffer\).foo ignoring self-assignment in b.buf1 = b.buf2\[1:2:3\]$"
 }
 
 func (b *Buffer) bar() { // ERROR "leaking param: b$"
@@ -1613,13 +1613,13 @@
 }
 
 func (b *Buffer) arrayPtr() { // ERROR "\(\*Buffer\).arrayPtr b does not escape"
-	b.buf1 = b.arrPtr[1:2]   // ERROR "\(\*Buffer\).arrayPtr ignoring self-assignment to b.buf1"
-	b.buf1 = b.arrPtr[1:2:3] // ERROR "\(\*Buffer\).arrayPtr ignoring self-assignment to b.buf1"
+	b.buf1 = b.arrPtr[1:2]   // ERROR "\(\*Buffer\).arrayPtr ignoring self-assignment in b.buf1 = b.arrPtr\[1:2\]$"
+	b.buf1 = b.arrPtr[1:2:3] // ERROR "\(\*Buffer\).arrayPtr ignoring self-assignment in b.buf1 = b.arrPtr\[1:2:3\]$"
 }
 
 func (b *Buffer) baz() { // ERROR "\(\*Buffer\).baz b does not escape$"
-	b.str1 = b.str1[1:2] // ERROR "\(\*Buffer\).baz ignoring self-assignment to b.str1$"
-	b.str1 = b.str2[1:2] // ERROR "\(\*Buffer\).baz ignoring self-assignment to b.str1$"
+	b.str1 = b.str1[1:2] // ERROR "\(\*Buffer\).baz ignoring self-assignment in b.str1 = b.str1\[1:2\]$"
+	b.str1 = b.str2[1:2] // ERROR "\(\*Buffer\).baz ignoring self-assignment in b.str1 = b.str2\[1:2\]$"
 }
 
 func (b *Buffer) bat() { // ERROR "leaking param content: b$"
@@ -1629,8 +1629,8 @@
 }
 
 func quux(sp *string, bp *[]byte) { // ERROR "quux bp does not escape$" "quux sp does not escape$"
-	*sp = (*sp)[1:2] // ERROR "quux ignoring self-assignment to \*sp$"
-	*bp = (*bp)[1:2] // ERROR "quux ignoring self-assignment to \*bp$"
+	*sp = (*sp)[1:2] // ERROR "quux ignoring self-assignment in \*sp = \(\*sp\)\[1:2\]$"
+	*bp = (*bp)[1:2] // ERROR "quux ignoring self-assignment in \*bp = \(\*bp\)\[1:2\]$"
 }
 
 type StructWithString struct {