cmd/compile: bce when max and limit are consts

Removes 49 more bound checks in make.bash. For example:

var a[100]int
for i := 0; i < 50; i++ {
  use a[i+25]
}

Change-Id: I85e0130ee5d07f0ece9b17044bba1a2047414ce7
Reviewed-on: https://go-review.googlesource.com/21379
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 14 insertions, 1 deletions

diff --git a/test/checkbce.go b/test/checkbce.go
index 988375fcc7..fa0ea12803 100644
--- a/test/checkbce.go
+++ b/test/checkbce.go
@@ -57,7 +57,7 @@ func f6(a [32]int, b [64]int, i int) {
 	useInt(b[uint64(i*0x07C4ACDD)>>58])
 	useInt(a[uint(i*0x07C4ACDD)>>59])
 
-	// The following bounds should removed as they can overflow.
+	// The following bounds should not be removed because they can overflow.
 	useInt(a[uint32(i*0x106297f105d0cc86)>>26]) // ERROR "Found IsInBounds$"
 	useInt(b[uint64(i*0x106297f105d0cc86)>>57]) // ERROR "Found IsInBounds$"
 	useInt(a[int32(i*0x106297f105d0cc86)>>26])  // ERROR "Found IsInBounds$"
@@ -89,6 +89,19 @@ func g3(a []int) {
 	}
 }
 
+func g4(a [100]int) {
+	for i := 10; i < 50; i++ {
+		useInt(a[i-10])
+		useInt(a[i])
+		useInt(a[i+25])
+		useInt(a[i+50])
+
+		// The following are out of bounds.
+		useInt(a[i-11]) // ERROR "Found IsInBounds$"
+		useInt(a[i+51]) // ERROR "Found IsInBounds$"
+	}
+}
+
 //go:noinline
 func useInt(a int) {
 }