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Re: [committed][PR rtl-optimization/87761] Limited iteration in regcprop to pick up secondary opportunities


On 3/24/19 11:11 AM, Segher Boessenkool wrote:
> Hi Jeff,
> 
> On Sun, Mar 24, 2019 at 09:20:07AM -0600, Jeff Law wrote:
>> +	PR rtl-optimization/87761
>> +	* regcprop.c (copyprop_hardreg_forward_1): Check may_trap_p on SET,
>> +	not INSN.  Also check RTX_FRAME_RELATED_P.  Queue insns for DF rescan
>> +	as needed.
> 
> Why the RTX_FRAME_RELATED_P addition?  You didn't explain it I think.  Is it
> just a bugfix, or something this patch exposed, something that couldn't
> happen before (or was harmless) and now isn't anymore?
It's just a bugfix -- one of the embedded targets needed it, I can't
offhand remember which -- we had a frame related insn with a REG_UNUSED
note which the code deleted causing a fault in the dwarf2cfi bits.

Thank goodness for Jenkins  scripts which will build and test all those
silly *-elf targets :-)


> 
> Or should this part be backported :-)
Shouldn't be needed as the code to remove insns with REG_UNUSED notes is
new for gcc-9.

jeff


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