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On Aug 6, 2012, at 10:45 AM, Vincent Lejeune <vljn at ovi.com> wrote: > Is it possible to "customise" INSERT_SUBREG and COPY instructions to add them an immediate operands ? > I know that COPY is lowered using copyPhysReg() function in MachineTargetInstrInfo, but I'm not sure there is something equivalent for INSERT_SUBREG. No, these instructions must be pure register copies. They can't have additional target-specific semantics. You would need to insert target-specific NEG and ABS instructions instead. /jakob

Hi, R600 hardware (Radeon gfx card) does neither have a NEG nor an ABS instruction ; however any sources operand can be negated/abs'd by setting a bit for every source operand in the final bytecode (but not DST). A good way of modeling this behavior in LLVM is by using TargetFlag on operand. Currently the R600 LLVM backend in Mesa lower NEG and ABS DAG instruction to a MOV + TargetFlag using