runtime: don't call funcPC from a function

The escape analysis support is not yet good enough to avoid escaping
    the argument to funcPC.  This causes unnecessary and often harmful
    memory allocation.  E.g., (*cpuProfile).addExtra can be called from a
    signal handler, and it must not allocate memory.
    
    Move the calls to funcPC to use variables instead.  This was done in
    the original migration to using funcPC, but was not done for newer code.
    
    In one case, in signal handling code, use getSigtramp.
    
    Reviewed-on: https://go-review.googlesource.com/92735

From-SVN: r257463

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-5fe998e4a18cc1dbbd4869be5c8202bda55adb33
+cdc28627b7abfd73f5d552813db8eb4293b823b0
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/runtime/cpuprof.go

@@ -156,8 +156,8 @@ func (p *cpuProfile) addExtra() {
 	if p.lostExtra > 0 {
 		hdr := [1]uint64{p.lostExtra}
 		lostStk := [2]uintptr{
-			funcPC(_LostExternalCode) + sys.PCQuantum,
-			funcPC(_ExternalCode) + sys.PCQuantum,
+			_LostExternalCodePC + sys.PCQuantum,
+			_ExternalCodePC + sys.PCQuantum,
 		}
 		cpuprof.log.write(nil, 0, hdr[:], lostStk[:])
 		p.lostExtra = 0
@@ -167,8 +167,8 @@ func (p *cpuProfile) addExtra() {
 func (p *cpuProfile) addLostAtomic64(count uint64) {
 	hdr := [1]uint64{count}
 	lostStk := [2]uintptr{
-		funcPC(_LostSIGPROFDuringAtomic64) + sys.PCQuantum,
-		funcPC(_System) + sys.PCQuantum,
+		_LostSIGPROFDuringAtomic64PC + sys.PCQuantum,
+		_SystemPC + sys.PCQuantum,
 	}
 	cpuprof.log.write(nil, 0, hdr[:], lostStk[:])
 }

libgo/go/runtime/proc.go

@@ -3369,7 +3369,9 @@ var lostAtomic64Count uint64
 
 var _SystemPC = funcPC(_System)
 var _ExternalCodePC = funcPC(_ExternalCode)
+var _LostExternalCodePC = funcPC(_LostExternalCode)
 var _GCPC = funcPC(_GC)
+var _LostSIGPROFDuringAtomic64PC = funcPC(_LostSIGPROFDuringAtomic64)
 
 // Called if we receive a SIGPROF signal.
 // Called by the signal handler, may run during STW.
@@ -3469,7 +3471,7 @@ func sigprofNonGoPC(pc uintptr) {
 	if prof.hz != 0 {
 		stk := []uintptr{
 			pc,
-			funcPC(_ExternalCode) + sys.PCQuantum,
+			_ExternalCodePC + sys.PCQuantum,
 		}
 		cpuprof.addNonGo(stk)
 	}

libgo/go/runtime/signal_unix.go

@@ -245,7 +245,7 @@ func setProcessCPUProfiler(hz int32) {
 		// Enable the Go signal handler if not enabled.
 		if atomic.Cas(&handlingSig[_SIGPROF], 0, 1) {
 			atomic.Storeuintptr(&fwdSig[_SIGPROF], getsig(_SIGPROF))
-			setsig(_SIGPROF, funcPC(sighandler))
+			setsig(_SIGPROF, getSigtramp())
 		}
 	} else {
 		// If the Go signal handler should be disabled by default,