cmd/compile: check for negative upper bound to IsSliceInBounds

IsSliceInBounds(x, y) asserts that y is not negative, but
there were cases where this is not true.  Change code
generation to ensure that this is true when it's not obviously
true.  Prove phase cleans a few of these out.

With this change the compiler text section is 0.06% larger,
that is, not very much.  Benchmarking still TBD, may need
to wait for access to a benchmarking box (next week).

Also corrected run.go to handle '?' in -update_errors output.

Fixes #28797.

Change-Id: Ia8af90bc50a91ae6e934ef973def8d3f398fac7b
Reviewed-on: https://go-review.googlesource.com/c/152477
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 9 insertions, 9 deletions

diff --git a/test/prove.go b/test/prove.go
index 79256893b3..0de6bd63b4 100644
--- a/test/prove.go
+++ b/test/prove.go
@@ -62,7 +62,7 @@ func f1c(a []int, i int64) int {
 }
 
 func f2(a []int) int {
-	for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1"
+	for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		a[i+1] = i
 		a[i+1] = i // ERROR "Proved IsInBounds$"
 	}
@@ -269,7 +269,7 @@ func f11b(a []int, i int) {
 
 func f11c(a []int, i int) {
 	useSlice(a[:i])
-	useSlice(a[:i]) // ERROR "Proved IsSliceInBounds$"
+	useSlice(a[:i]) // ERROR "Proved Geq64$" "Proved IsSliceInBounds$"
 }
 
 func f11d(a []int, i int) {
@@ -464,12 +464,12 @@ func f16(s []int) []int {
 }
 
 func f17(b []int) {
-	for i := 0; i < len(b); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1"
+	for i := 0; i < len(b); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
 		// This tests for i <= cap, which we can only prove
 		// using the derived relation between len and cap.
 		// This depends on finding the contradiction, since we
 		// don't query this condition directly.
-		useSlice(b[:i]) // ERROR "Proved IsSliceInBounds$"
+		useSlice(b[:i]) // ERROR "Proved Geq64$" "Proved IsSliceInBounds$"
 	}
 }
 
@@ -579,18 +579,18 @@ func fence4(x, y int64) {
 func trans1(x, y int64) {
 	if x > 5 {
 		if y > x {
-			if y > 2 { // ERROR "Proved Greater64"
+			if y > 2 { // ERROR "Proved Greater64$"
 				return
 			}
 		} else if y == x {
-			if y > 5 { // ERROR "Proved Greater64"
+			if y > 5 { // ERROR "Proved Greater64$"
 				return
 			}
 		}
 	}
 	if x >= 10 {
 		if y > x {
-			if y > 10 { // ERROR "Proved Greater64"
+			if y > 10 { // ERROR "Proved Greater64$"
 				return
 			}
 		}
@@ -624,7 +624,7 @@ func natcmp(x, y []uint) (r int) {
 	}
 
 	i := m - 1
-	for i > 0 && // ERROR "Induction variable: limits \(0,\?\], increment 1"
+	for i > 0 && // ERROR "Induction variable: limits \(0,\?\], increment 1$"
 		x[i] == // ERROR "Proved IsInBounds$"
 			y[i] { // ERROR "Proved IsInBounds$"
 		i--
@@ -686,7 +686,7 @@ func range2(b [][32]int) {
 		if i < len(b) {    // ERROR "Proved Less64$"
 			println("x")
 		}
-		if i >= 0 { // ERROR "Proved Geq64"
+		if i >= 0 { // ERROR "Proved Geq64$"
 			println("x")
 		}
 	}