search for: dldregsxptrreg

...of the regclasses involved to show what i mean: DREGS: R31R30, R29R28 down to R1R0 (16 regs) DLDREGS: R31R30, R29R28 down to R17R16 (8 regs) PTRREGS: R31R30, R29R28, R27R26 (3 regs) All classes intersect each other giving as a result the smaller class: DREGSxDLDREGS=DLDREGS / DLDREGSxPTRREGS=PTRREGS, etc. That's why i think the coalescer should work since the regclasses overlap completely. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20110326/16792fdd/attachment.html>

On Mar 24, 2011, at 5:42 PM, Borja Ferrer wrote: > The last copy instruction should be removed as pointed out above, but since R27R26 is killed in the load instruction it has to be emitted. About the insane amount of regclasses there, the load/store and the andi instructions take subsets of regs from the main register class, they cant work with all registers, that's why STW and LDW needs

Hello, I've noticed the following issue while testing some codegen tests, i would like to know if it's a missed optimization or i missed something out here. This is for an out of tree backend im writing. I managed to reduce it to the following C function: void foo(int *a) // int here is 16bits { *a &= 0xFF; } This is the code before regalloc: Live Ins: %R25R24

...show what i mean: > > DREGS: R31R30, R29R28 down to R1R0 (16 regs) > DLDREGS: R31R30, R29R28 down to R17R16 (8 regs) > PTRREGS: R31R30, R29R28, R27R26 (3 regs) > > All classes intersect each other giving as a result the smaller class: DREGSxDLDREGS=DLDREGS / DLDREGSxPTRREGS=PTRREGS, etc. That's why i think the coalescer should work since the regclasses overlap completely. Cross class coalescing also has some heuristics to prevent it from creating very small register classes. It is possible that it doesn't want to use PTRREGS because it only has 3 registers....