internal/bisect: add 'q' hash option for quiet hash behavior switching

This is intended for the specific case of 'fmahash=qn' where someone
wants to disable fma without all the hash-search-handshake output.
There are cases where arm64, ppc64, and s390x users might want to do
this.

Change-Id: Iaf46c68a00d7c9f7f82fd98a4548b72610f84bed
Reviewed-on: https://go-review.googlesource.com/c/go/+/503776
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/internal/bisect/bisect.go b/src/internal/bisect/bisect.go
index 37f76a42718496a7d66f7bfbc18824229a06cbdc..48c796e54ac7340163a57e427f19ff8bf9398a05 100644 (file)
--- a/src/internal/bisect/bisect.go
+++ b/src/internal/bisect/bisect.go
@@ -198,10 +198,20 @@ func New(pattern string) (*Matcher, error) {
 
        m := new(Matcher)
 
-       // Allow multiple v, so that “bisect cmd vPATTERN” can force verbose all the time.
        p := pattern
+       // Special case for leading 'q' so that 'qn' quietly disables, e.g. fmahash=qn to disable fma
+       // Any instance of 'v' disables 'q'.
+       if len(p) > 0 && p[0] == 'q' {
+               m.quiet = true
+               p = p[1:]
+               if p == "" {
+                       return nil, &parseError{"invalid pattern syntax: " + pattern}
+               }
+       }
+       // Allow multiple v, so that “bisect cmd vPATTERN” can force verbose all the time.
        for len(p) > 0 && p[0] == 'v' {
                m.verbose = true
+               m.quiet = false
                p = p[1:]
                if p == "" {
                        return nil, &parseError{"invalid pattern syntax: " + pattern}
@@ -297,7 +307,8 @@ func New(pattern string) (*Matcher, error) {
 // A Matcher is the parsed, compiled form of a PATTERN string.
 // The nil *Matcher is valid: it has all changes enabled but none reported.
 type Matcher struct {
-       verbose bool
+       verbose bool   // annotate reporting with human-helpful information
+       quiet   bool   // disables all reporting.  reset if verbose is true. use case is -d=fmahash=qn
        enable  bool   // when true, list is for “enable and report” (when false, “disable and report”)
        list    []cond // conditions; later ones win over earlier ones
        dedup   atomicPointerDedup
@@ -339,20 +350,19 @@ func (m *Matcher) ShouldEnable(id uint64) bool {
        if m == nil {
                return true
        }
-       for i := len(m.list) - 1; i >= 0; i-- {
-               c := &m.list[i]
-               if id&c.mask == c.bits {
-                       return c.result == m.enable
-               }
-       }
-       return false == m.enable
+       return m.matchResult(id) == m.enable
 }
 
 // ShouldPrint reports whether to print identifying information about the change with the given id.
 func (m *Matcher) ShouldPrint(id uint64) bool {
-       if m == nil {
+       if m == nil || m.quiet {
                return false
        }
+       return m.matchResult(id)
+}
+
+// matchResult returns the result from the first condition that matches id.
+func (m *Matcher) matchResult(id uint64) bool {
        for i := len(m.list) - 1; i >= 0; i-- {
                c := &m.list[i]
                if id&c.mask == c.bits {