search for: v1645

...gt; %v1177 = undef >> ... >> loop: >> ... >> %v1176 = op ... >> = %v1177 >> %v1177 = %v1176 >> jmp loop >> >> Why is not safe to coalesce the 2 registers? > > Not quite. The original code is: > > %v1177 = undef > %v1645 = ... > loop: > %v1176 = %v1645 > ... > = %v1176 > = %v1177 > %v1645 = op ... > %v1177 = %v1176 > jmp loop > > We can't coalesce %v1177 and %v1176 legally. But we do. Seriously, why not? In the first iteration, it's totally legal for v1177 has the same v...

...... > >> %v1176 = op ... > >> = %v1177 > >> %v1177 = %v1176 > >> jmp loop > >> > >> Why is not safe to coalesce the 2 registers? > > > > Not quite. The original code is: > > > > %v1177 = undef > > %v1645 = ... > > loop: > > %v1176 = %v1645 > > ... > > = %v1176 > > = %v1177 > > %v1645 = op ... > > %v1177 = %v1176 > > jmp loop > > > > We can't coalesce %v1177 and %v1176 legally. But we do. > > Seriously, why not? In the first i...

...p ... >>>> = %v1177 >>>> %v1177 = %v1176 >>>> jmp loop >>>> >>>> Why is not safe to coalesce the 2 registers? >>> >>> Not quite. The original code is: >>> >>> %v1177 = undef >>> %v1645 = ... >>> loop: >>> %v1176 = %v1645 >>> ... >>> = %v1176 >>> = %v1177 >>> %v1645 = op ... >>> %v1177 = %v1176 >>> jmp loop >>> >>> We can't coalesce %v1177 and %v1176 legally. But we do. >> >&gt...

On Monday 02 February 2009 23:55, Evan Cheng wrote: > >> Think about what will happen the 2nd iteration.  %v1177 will have > >> the value of > >> %v1645 which is wrong.  This is because %v1176 in bb74 will be > >> replaced with > >> %v1177.  That's incorrect. > > > > Ok, right. The trick to fixing is to make sure the valno of the def of > > v1177 hasPHIKill to true and make sure the coalescer checks it. What...

On Feb 5, 2009, at 5:30 PM, David Greene wrote: > On Monday 02 February 2009 23:55, Evan Cheng wrote: > >>>> Think about what will happen the 2nd iteration. %v1177 will have >>>> the value of >>>> %v1645 which is wrong. This is because %v1176 in bb74 will be >>>> replaced with >>>> %v1177. That's incorrect. >>> >>> Ok, right. The trick to fixing is to make sure the valno of the >>> def of >>> v1177 hasPHIKill to true and make sure...

...really follow it. Is this what you are describing? > > %v1177 = undef > ... > loop: > ... > %v1176 = op ... > = %v1177 > %v1177 = %v1176 > jmp loop > > Why is not safe to coalesce the 2 registers? Not quite. The original code is: %v1177 = undef %v1645 = ... loop: %v1176 = %v1645 ... = %v1176 = %v1177 %v1645 = op ... %v1177 = %v1176 jmp loop We can't coalesce %v1177 and %v1176 legally. But we do. -Dave

...= %v1177 >>>>> %v1177 = %v1176 >>>>> jmp loop >>>>> >>>>> Why is not safe to coalesce the 2 registers? >>>> >>>> Not quite. The original code is: >>>> >>>> %v1177 = undef >>>> %v1645 = ... >>>> loop: >>>> %v1176 = %v1645 >>>> ... >>>> = %v1176 >>>> = %v1177 >>>> %v1645 = op ... >>>> %v1177 = %v1176 >>>> jmp loop >>>> >>>> We can't coalesce %v1177 and %v11...

On Feb 2, 2009, at 10:08 AM, David Greene wrote: > On Friday 30 January 2009 16:54, Evan Cheng wrote: > >> I don't have the whole context to understand why you think this is a >> bug. An implicit_def doesn't actually define any value. So we don't >> care if a live interval overlaps live ranges defined by an >> implicit_def. > > It's a bug