On Wed, 2015-07-22 at 16:45 -0700, Stephen Boyd wrote: > On 07/22, Andy Shevchenko wrote: > > On Tue, 2015-07-21 at 17:41 -0700, Stephen Boyd wrote: > > > On 07/14, Andy Shevchenko wrote: > > > > diff --git a/drivers/clk/clk-fractional-divider.c > > > > b/drivers/clk/clk > > > > -fractional-divider.c > > > > index 7cfcc56..16f42ae 100644 > > > > --- a/drivers/clk/clk-fractional-divider.c > > > > +++ b/drivers/clk/clk-fractional-divider.c > > > > @@ -128,9 +128,11 @@ struct clk > > > > *clk_register_fractional_divider(struct device *dev, > > > > > > > > fd->reg = reg; > > > > fd->mshift = mshift; > > > > - fd->mmask = (BIT(mwidth) - 1) << mshift; > > > > + fd->mwidth = mwidth; > > > > + fd->mmask = GENMASK(mwidth - 1, 0) << mshift; > > > > fd->nshift = nshift; > > > > - fd->nmask = (BIT(nwidth) - 1) << nshift; > > > > + fd->nwidth = nwidth; > > > > + fd->nmask = GENMASK(nwidth - 1, 0) << nshift; > > > > > > Please do the shifts in the GENMASK. > > > > It's not optimal. Waste of performance. > > > > 32-bit case on 32-bit machine (similar to other cases on x86). > > > > a) GENMASK(x - 1, 0) << y > > > > movl $32, %ecx > > subb 4(%esp), %cl > > movl $-1, %eax > > shrl %cl, %eax > > movzbl 8(%esp), %ecx > > sall %cl, %eax > > ret > > > > b) GENMASK(x + y - 1, y) > > > > pushl %esi > > pushl %ebx > > movl $1, %edx > > movzbl 12(%esp), %eax > > movzbl 16(%esp), %esi > > movl $-1, %ebx > > subl %eax, %edx > > movl %ebx, %eax > > subl %esi, %edx > > leal 31(%edx), %ecx > > shrl %cl, %eax > > movl %esi, %ecx > > sall %cl, %ebx > > andl %ebx, %eax > > popl %ebx > > popl %esi > > ret > > > > This is not hotpath code, so why do we care?
I care about memory foot print of kernel's .text as well. -- Andy Shevchenko <andriy.shevche...@linux.intel.com> Intel Finland Oy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
