[LLVMdev] Remove subreg copies

[Ivan Llopard]

Hi,

I'm facing a problem in my BE while trying to remove certain copies. 
Here is a code snippet which I would like to optimize

%vreg1<def> = READF32r; vRRegs:%vreg1
%vreg2<def> = COPY %vreg1:rsub_h; iRSubRegs:%vreg2 vRRegs:%vreg1
%vreg3<def> = COPY %vreg1:rsub_l; iRSubRegs:%vreg3 vRRegs:%vreg1

This code produces subreg-to-subreg copies but I would like to have 
direct uses of vreg1's subregisters instead.
I tried to add RAhints in order to form identity copies (vreg1 and 
vreg2/3 should be allocated to the same sub/super register) and let the 
RA removes them automatically but it didn't work on all the copies. Is 
there another method to get rid of these copies whenever possible ?

Ivan