libgo: update to Go1.10beta1

    
    Update the Go library to the 1.10beta1 release.
    
    Requires a few changes to the compiler for modifications to the map
    runtime code, and to handle some nowritebarrier cases in the runtime.
    
    Reviewed-on: https://go-review.googlesource.com/86455

gotools/:
	* Makefile.am (go_cmd_vet_files): New variable.
	(go_cmd_buildid_files, go_cmd_test2json_files): New variables.
	(s-zdefaultcc): Change from constants to functions.
	(noinst_PROGRAMS): Add vet, buildid, and test2json.
	(cgo$(EXEEXT)): Link against $(LIBGOTOOL).
	(vet$(EXEEXT)): New target.
	(buildid$(EXEEXT)): New target.
	(test2json$(EXEEXT)): New target.
	(install-exec-local): Install all $(noinst_PROGRAMS).
	(uninstall-local): Uninstasll all $(noinst_PROGRAMS).
	(check-go-tool): Depend on $(noinst_PROGRAMS).  Copy down
	objabi.go.
	(check-runtime): Depend on $(noinst_PROGRAMS).
	(check-cgo-test, check-carchive-test): Likewise.
	(check-vet): New target.
	(check): Depend on check-vet.  Look at cmd_vet-testlog.
	(.PHONY): Add check-vet.
	* Makefile.in: Rebuild.

From-SVN: r256365

1 files changed, 12 insertions, 5 deletions

diff --git a/libgo/go/math/dim.go b/libgo/go/math/dim.go
index 37ab538..cf06f30 100644
--- a/libgo/go/math/dim.go
+++ b/libgo/go/math/dim.go
@@ -11,11 +11,18 @@ package math
 //	Dim(-Inf, -Inf) = NaN
 //	Dim(x, NaN) = Dim(NaN, x) = NaN
 func Dim(x, y float64) float64 {
-	return dim(x, y)
-}
-
-func dim(x, y float64) float64 {
-	return max(x-y, 0)
+	// The special cases result in NaN after the subtraction:
+	//      +Inf - +Inf = NaN
+	//      -Inf - -Inf = NaN
+	//       NaN - y    = NaN
+	//         x - NaN  = NaN
+	v := x - y
+	if v <= 0 {
+		// v is negative or 0
+		return 0
+	}
+	// v is positive or NaN
+	return v
 }
 
 // Max returns the larger of x or y.