runtime: remove scase.releasetime field

This is the gofrontend version of https://golang.org/cl/245122.
Original CL description:

    selectgo will report at most one block event, so there's no need to
    keep a releasetime for every select case. It suffices to simply track
    the releasetime of the case responsible for the wakeup.

    Updates golang/go#40410.

This is being brought over to gofrontend as a step toward upgrading to
Go1.16beta1.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/279732

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 81deef2cb79e38a19a5c65376716913201f3fca3..bfc7856cce516fccdb21b42c3d07d65019a4a793 100644 (file)
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-f9e44c6e510df9f047dbe28eb5fa19642e350f8f
+c8456995b0118a92820c6c1d8f996d4b1adf55c2
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

diff --git a/gcc/go/gofrontend/types.cc b/gcc/go/gofrontend/types.cc
index ecb93b099dbc5b063d507aa2092a426202292ba9..12e783010db3291421bec3a3db802bbacb28c406 100644 (file)
--- a/gcc/go/gofrontend/types.cc
+++ b/gcc/go/gofrontend/types.cc
@@ -8908,11 +8908,10 @@ Channel_type::select_case_type()
       Type* uint16_type = Type::lookup_integer_type("uint16");
       Type* int64_type = Type::lookup_integer_type("int64");
       scase_type =
-       Type::make_builtin_struct_type(4,
+       Type::make_builtin_struct_type(3,
                                       "c", unsafe_pointer_type,
                                       "elem", unsafe_pointer_type,
-                                      "kind", uint16_type,
-                                      "releasetime", int64_type);
+                                      "kind", uint16_type);
       scase_type->set_is_struct_incomparable();
     }
   return scase_type;

diff --git a/libgo/go/runtime/select.go b/libgo/go/runtime/select.go
index c8910b8dc237f7a5fc2cc375f3ced8fc08c0ba10..81e00ec5a4e5c676d5011caead489c7ddf82afe3 100644 (file)
--- a/libgo/go/runtime/select.go
+++ b/libgo/go/runtime/select.go
@@ -32,10 +32,9 @@ const (
 // Known to compiler.
 // Changes here must also be made in src/cmd/internal/gc/select.go's scasetype.
 type scase struct {
-       c           *hchan         // chan
-       elem        unsafe.Pointer // data element
-       kind        uint16
-       releasetime int64
+       c    *hchan         // chan
+       elem unsafe.Pointer // data element
+       kind uint16
 }
 
 func sellock(scases []scase, lockorder []uint16) {
@@ -151,9 +150,6 @@ func selectgo(cas0 *scase, order0 *uint16, ncases int) (int, bool) {
        var t0 int64
        if blockprofilerate > 0 {
                t0 = cputicks()
-               for i := 0; i < ncases; i++ {
-                       scases[i].releasetime = -1
-               }
        }
 
        // The compiler rewrites selects that statically have
@@ -241,6 +237,7 @@ loop:
        var dfl *scase
        var casi int
        var cas *scase
+       var caseReleaseTime int64 = -1
        var recvOK bool
        for i := 0; i < ncases; i++ {
                casi = int(pollorder[i])
@@ -361,13 +358,13 @@ loop:
                if k.kind == caseNil {
                        continue
                }
-               if sglist.releasetime > 0 {
-                       k.releasetime = sglist.releasetime
-               }
                if sg == sglist {
                        // sg has already been dequeued by the G that woke us up.
                        casi = int(casei)
                        cas = k
+                       if sglist.releasetime > 0 {
+                               caseReleaseTime = sglist.releasetime
+                       }
                } else {
                        c = k.c
                        if k.kind == caseSend {
@@ -465,8 +462,8 @@ send:
        goto retc
 
 retc:
-       if cas.releasetime > 0 {
-               blockevent(cas.releasetime-t0, 1)
+       if caseReleaseTime > 0 {
+               blockevent(caseReleaseTime-t0, 1)
        }
 
        // Check preemption, since unlike gc we don't check on every call.