cmd/compile: ppc64le: Invalid n or b for CLRLSLDI: 30 28

[ianlancetaylor]

On current tip (874b313, CL 247477) this valid code gets an incorrect compilation error with GOARCH=ppc64le.

I believe this is due to CL 252097. CC @laboger @ceseo @pmur

package p

func F(s int32, n uint64) uint64 {
	c := (s >> 1) & 0xffffff
	return uint64(c)<<48
}

This is the compilation error with GOARCH=ppc64le. Note the missing %v message.

foo.go:5:2: Invalid n or b for CLRLSLDI: 30 28
%!v(MISSING)

[ceseo]

Looking into it.

[laboger]

I see the problem. The rules that use AND need to do more checking of mask length and shift count.

[gopherbot]

Change https://golang.org/cl/258138 mentions this issue: cmd/compile,cmd/internal/obj/ppc64: fix some shift rules due to a regression