Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version devel +fa49c39 Tue Oct 4 17:22:14 2016 +0000 linux/ppc64le

What operating system and processor architecture are you using (go env)?

Ubuntu 16.04 ppc64le

What did you do?

Looked at generated code in areas where performance could be improved.

What did you expect to see?

No code sequences to generate carry if the shift count is constant.

What did you see instead?

Code sequences like this
12a24: 0d 00 a0 38 li r5,13
12a28: c0 ff e5 33 addic r31,r5,-64
12a2c: d4 01 c0 7c addme r6,r0
12a30: 38 33 a5 7c orc r5,r5,r6
12a34: 36 2c 84 7c srd r4,r4,r5

Changes to PPC64.rules can improve this.