cmd/8g: don't allocate a register early for cap(CHAN).

There is no reason to generate different code for cap and len.

Fixes issue 8025.
Fixes issue 8026.

LGTM=rsc
R=rsc, iant, khr
CC=golang-codereviews
https://codereview.appspot.com/93570044

1 files changed, 7 insertions, 0 deletions

diff --git a/test/torture.go b/test/torture.go
index bbf6d347d..197b481e6 100644
--- a/test/torture.go
+++ b/test/torture.go
@@ -337,3 +337,10 @@ func ChainDivConst(a int) int {
 func ChainMulBytes(a, b, c byte) byte {
 	return a*(a*(a*(a*(a*(a*(a*(a*(a*b+c)+c)+c)+c)+c)+c)+c)+c) + c
 }
+
+func ChainCap() {
+	select {
+	case <-make(chan int, cap(make(chan int, cap(make(chan int, cap(make(chan int, cap(make(chan int))))))))):
+	default:
+	}
+}