Re: [llvm-commits] SHR Patch (Updated) #2/3 [noninstcombine part]

[Chris Lattner]

On Nov 2, 2006, at 3:33 PM, Reid Spencer wrote: Here are the SHR patches updated for recent changes on the HEAD. These replace the previous submission on Tuesday.  If you're reviewing the SHR patches, please use this version now. ***NOTE: This is for review only, please don't commit any of this. Reid. <SHR.patch> <SHR.llvmgcc.patch> *** In LangRef.html, please make the "Overview" sections of each instr mention the word "logical" or "arithmetic". *** In a follow-on patch, please replace all uses of ConstantExpr::get[US]Shr with ConstantExpr::get[LA]Shr.  Please do this after committing this patch though, to ease review. *** I should have asked for this before, but in CWriter::printConstExprCast, please name 'result' something more useful, like "NeedsExplicitCast" or something.  likewise in writeInstructionCast. *** In SROA::ConvertUsesToScalar, the shift should always be a logical shift.  Since the top bits are truncated away, it doesn't matter which one you use and lshr is cheaper. *** In ConstantFolding.cpp, all of these cases:    static Constant *Shl(const ConstantPacked *V1, const ConstantPacked *V2) {      return EvalVectorOp(V1, V2, ConstantExpr::getShl);    } -  static Constant *Shr(const ConstantPacked *V1, const ConstantPacked *V2) { -    return EvalVectorOp(V1, V2, ConstantExpr::getShr); +  static Constant *LShr(const ConstantPacked *V1, const ConstantPacked *V2) { +    return EvalVectorOp(V1, V2, ConstantExpr::getLShr); +  } +  static Constant *AShr(const ConstantPacked *V1, const ConstantPacked *V2) { +    return EvalVectorOp(V1, V2, ConstantExpr::getAShr);    } are dead, because we don't support shifting of vectors. *** In ConstantFolding.cpp, this comment is incorrect: +    case Instruction::AShr: +      if (!isa<UndefValue>(V2)) +        return const_cast<Constant*>(V1);           // undef ashr X --> X It is actually "... --> undef". Otherwise, looks good. -Chris

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