[llvm-commits] [llvm] r161728 - in /llvm/trunk: lib/CodeGen/MachineCSE.cpp test/CodeGen/X86/lsr-loop-exit-cond.ll test/CodeGen/X86/machine-cse.ll

[Benjamin Kramer]

On 11.08.2012, at 22:09, Jakob Stoklund Olesen <stoklund at 2pi.dk> wrote:

> 
> On Aug 11, 2012, at 12:05 PM, Benjamin Kramer <benny.kra at googlemail.com> wrote:
> 
>> Author: d0k
>> Date: Sat Aug 11 14:05:13 2012
>> New Revision: 161728
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=161728&view=rev
>> Log:
>> PR13578: Teach MachineCSE that instructions that use a constant register can be CSE'd safely.
>> 
>> This is common e.g. when doing rip-relative addressing on x86_64.
> 
> Nice.
> 
>> -    for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
>> -      PhysRefs.insert(*AI);
>> +    for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
>> +      // Reading constant physregs is ok.
>> +      if (!MRI->isConstantPhysReg(*AI, *MBB->getParent()))
>> +        PhysRefs.insert(*AI);
> 
> It's safe to swap 'if' and 'for' here. The isConstantPhysReg() function already checks all aliases.

Fixed in r161729. Thanks Jakob!

- Ben