cmd/compile: enable optimizer logging for bounds checking

Change-Id: Ic1fc271589b7212e7f604ece93cfe34feff909b2
Reviewed-on: https://go-review.googlesource.com/c/go/+/204160
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/compile/internal/logopt/logopt_test.go

@@ -20,12 +20,15 @@ type pair struct {a,b int}
 func bar(y *pair) *int {
 	return &y.b
 }
-
+var a []int
 func foo(w, z *pair) *int {
 	if *bar(w) > 0 {
 		return bar(z)
 	}
-	return nil
+	if a[1] > 0 {
+		a = a[:2]
+	}
+	return &a[0]
 }
 `
 
@@ -102,6 +105,7 @@ func TestLogOpt(t *testing.T) {
 		t.Logf("%s", slogged)
 		// below shows proper inlining and nilcheck
 		want(t, slogged, `{"range":{"start":{"line":9,"character":13},"end":{"line":9,"character":13}},"severity":3,"code":"nilcheck","source":"go compiler","message":"","relatedInformation":[{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":4,"character":11},"end":{"line":4,"character":11}}},"message":"inlineLoc"}]}`)
+		want(t, slogged, `{"range":{"start":{"line":11,"character":6},"end":{"line":11,"character":6}},"severity":3,"code":"isInBounds","source":"go compiler","message":""}`)
 	})
 }
 

src/cmd/compile/internal/ssa/checkbce.go

@@ -4,20 +4,32 @@
 
 package ssa
 
+import "cmd/compile/internal/logopt"
+
 // checkbce prints all bounds checks that are present in the function.
 // Useful to find regressions. checkbce is only activated when with
 // corresponding debug options, so it's off by default.
 // See test/checkbce.go
 func checkbce(f *Func) {
-	if f.pass.debug <= 0 {
+	if f.pass.debug <= 0 && !logopt.Enabled() {
 		return
 	}
 
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			if v.Op == OpIsInBounds || v.Op == OpIsSliceInBounds {
+				if f.pass.debug > 0 {
 					f.Warnl(v.Pos, "Found %v", v.Op)
 				}
+				if logopt.Enabled() {
+					if v.Op == OpIsInBounds {
+						logopt.LogOpt(v.Pos, "isInBounds", "checkbce", f.Name)
+					}
+					if v.Op == OpIsSliceInBounds {
+						logopt.LogOpt(v.Pos, "isSliceInBounds", "checkbce", f.Name)
+					}
+				}
+			}
 		}
 	}
 }