cmd/compile: add a pass to print bound checks

Since BCE happens over several passes (opt, loopbce, prove)
it's easy to regress especially with rewriting.

The pass is only activated with special debug flag.

Change-Id: I46205982e7a2751156db8e875d69af6138068f59
Reviewed-on: https://go-review.googlesource.com/21510
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

1 files changed, 89 insertions, 0 deletions

diff --git a/test/checkbce.go b/test/checkbce.go
new file mode 100644
index 0000000000..a3b0100db8
--- /dev/null
+++ b/test/checkbce.go
@@ -0,0 +1,89 @@
+// +build amd64
+// errorcheck -0 -d=ssa/check_bce/debug=3
+
+package main
+
+func f0(a []int) {
+	a[0] = 1 // ERROR "Found IsInBounds$"
+	a[0] = 1
+	a[6] = 1 // ERROR "Found IsInBounds$"
+	a[6] = 1
+	a[5] = 1
+	a[5] = 1
+}
+
+func f1(a [256]int, i int) {
+	useInt(a[i])     // ERROR "Found IsInBounds$"
+	useInt(a[i%256]) // ERROR "Found IsInBounds$"
+	useInt(a[i&255])
+	useInt(a[i&17])
+
+	if 4 <= i && i < len(a) {
+		useInt(a[i])
+		useInt(a[i-1]) // ERROR "Found IsInBounds$"
+		useInt(a[i-4]) // ERROR "Found IsInBounds$"
+	}
+}
+
+func f2(a [256]int, i uint) {
+	useInt(a[i]) // ERROR "Found IsInBounds$"
+	useInt(a[i%256])
+	useInt(a[i&255])
+	useInt(a[i&17])
+}
+
+func f3(a [256]int, i uint8) {
+	useInt(a[i])
+	useInt(a[i+10])
+	useInt(a[i+14])
+}
+
+func f4(a [27]int, i uint8) {
+	useInt(a[i%15])
+	useInt(a[i%19])
+	useInt(a[i%27])
+}
+
+func f5(a []int) {
+	if len(a) > 5 {
+		useInt(a[5])
+		useSlice(a[6:])
+		useSlice(a[:6]) // ERROR "Found IsSliceInBounds$"
+	}
+}
+
+func g1(a []int) {
+	for i := range a {
+		a[i] = i
+		useSlice(a[:i+1])
+		useSlice(a[:i])
+	}
+}
+
+func g2(a []int) {
+	useInt(a[3]) // ERROR "Found IsInBounds$"
+	useInt(a[2])
+	useInt(a[1])
+	useInt(a[0])
+}
+
+func g3(a []int) {
+	for i := range a[:256] { // ERROR "Found IsSliceInBounds$"
+		useInt(a[i]) // ERROR "Found IsInBounds$"
+	}
+	b := a[:256]
+	for i := range b {
+		useInt(b[i])
+	}
+}
+
+//go:noinline
+func useInt(a int) {
+}
+
+//go:noinline
+func useSlice(a []int) {
+}
+
+func main() {
+}