[llvm-dev] Lowering Select to Two Predicated Movs

Friedman, Eli via llvm-dev llvm-dev at lists.llvm.org
Fri Jul 7 12:37:23 PDT 2017

On 7/7/2017 12:10 PM, Dilan Manatunga wrote:
> My bad for not looking further. I'm still somewhat confused though. 
> MOVCCr gets expanded in the ARMExpandPseudoInsts pass, and it still 
> seems only a case of one instruction replacing the other.

The output of MOVCCr is tied to the "false" input using RegConstraint.  
The register allocator puts the "false" value into the destination 
register, then MOVCCr gets expanded to a predicated MOVr which moves the 
"true" value into the destination register.


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