Re: [PR64164] drop copyrename, integrate into expand

[Jeff Law <law@redhat.com>]

On 11/10/2015 03:58 PM, Alexandre Oliva wrote:
> On Nov 10, 2015, Alan Lawrence <alan.lawrence@arm.com> wrote:
>
>> FAIL: gcc.target/aarch64/aapcs64/func-ret-4.c execution,  -O2
>
> Ugh, sorry.  I even checked that testcase by hand before submitting the
> patch, because I knew it took the paths I was changing, but I didn't
> realize the stack store and load would amount to shifts when the stack
> slot was bypassed.
>
> With the following patch, we get a lsr and a ubfx, without the sp
> adjustments.  Please let me know if it causes any further problems.  So
> far, I've tested it on x86_64-linux-gnu, i686-linux-gnu, and
> ppc64le-linux-gnu; the ppc64-linux-gnu test run is running slower and
> probably won't be done before I call it a day, but I wanted to give you
> something before taking off for the day.
>
> Is this ok to install if ppc64-linux-gnu also regstraps successfully?
>
>
> [PR67753] adjust for padding when bypassing memory in assign_parm_setup_block
>
> From: Alexandre Oliva <aoliva@redhat.com>
>
> Storing a register in memory as a full word and then accessing the
> same memory address under a smaller-than-word mode amounts to
> right-shifting of the register word on big endian machines.  So, if
> BLOCK_REG_PADDING chooses upward padding for BYTES_BIG_ENDIAN, and
> we're copying from the entry_parm REG directly to a pseudo, bypassing
> any stack slot, perform the shifting explicitly.
>
> This fixes the miscompile of function_return_val_10 in
> gcc.target/aarch64/aapcs64/func-ret-4.c for target aarch64_be-elf
> introduced in the first patch for 67753.
>
> for  gcc/ChangeLog
>
> 	PR rtl-optimization/67753
> 	PR rtl-optimization/64164
> 	* function.c (assign_parm_setup_block): Right-shift
> 	upward-padded big-endian args when bypassing the stack slot.
Don't you need to check the value of BLOCK_REG_PADDING at runtime?  The 
padding is essentially allowed to vary.

If you  look at the other places where BLOCK_REG_PADDING is used, it's 
checked in a #ifdef, then again inside a if conditional.



Jeff