[llvm-commits] [llvm] r80963 - in /llvm/trunk: include/llvm/CodeGen/FastISel.h lib/CodeGen/SelectionDAG/FastISel.cpp test/CodeGen/X86/fast-isel-fneg.ll

[Chris Lattner]

On Sep 3, 2009, at 3:53 PM, Dan Gohman wrote:

> Author: djg
> Date: Thu Sep  3 17:53:57 2009
> New Revision: 80963
>
> URL: http://llvm.org/viewvc/llvm-project?rev=80963&view=rev
> Log:
> LLVM currently represents floating-point negation as -0.0 - x. Fix
> FastISel to recognize this pattern and emit a floating-point
> negation using xor.

ISD::XOR is legal for floating point operands?

-Chris

>
> Added:
>    llvm/trunk/test/CodeGen/X86/fast-isel-fneg.ll
> Modified:
>    llvm/trunk/include/llvm/CodeGen/FastISel.h
>    llvm/trunk/lib/CodeGen/SelectionDAG/FastISel.cpp
>
> Modified: llvm/trunk/include/llvm/CodeGen/FastISel.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/FastISel.h?rev=80963&r1=80962&r2=80963&view=diff
>
> =
> =
> =
> =
> =
> =
> =
> =
> ======================================================================
> --- llvm/trunk/include/llvm/CodeGen/FastISel.h (original)
> +++ llvm/trunk/include/llvm/CodeGen/FastISel.h Thu Sep  3 17:53:57  
> 2009
> @@ -300,6 +300,8 @@
> private:
>   bool SelectBinaryOp(User *I, ISD::NodeType ISDOpcode);
>
> +  bool SelectFNeg(User *I);
> +
>   bool SelectGetElementPtr(User *I);
>
>   bool SelectCall(User *I);
>
> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/FastISel.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/FastISel.cpp?rev=80963&r1=80962&r2=80963&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/FastISel.cpp (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/FastISel.cpp Thu Sep  3  
> 17:53:57 2009
> @@ -608,6 +608,26 @@
>   MBB->addSuccessor(MSucc);
> }
>
> +/// SelectFNeg - Emit an FNeg operation.
> +///
> +bool
> +FastISel::SelectFNeg(User *I) {
> +  unsigned OpReg = getRegForValue(BinaryOperator::getFNegArgument 
> (I));
> +  if (OpReg == 0) return false;
> +
> +  // Twiddle the sign bit with xor.
> +  EVT VT = TLI.getValueType(I->getType());
> +  if (VT.getSizeInBits() > 64) return false;
> +  unsigned ResultReg = FastEmit_ri_(VT.getSimpleVT(), ISD::XOR,  
> OpReg,
> +                                    UINT64_C(1) << (VT.getSizeInBits 
> ()-1),
> +                                    VT.getSimpleVT());
> +  if (ResultReg == 0)
> +    return false;
> +
> +  UpdateValueMap(I, ResultReg);
> +  return true;
> +}
> +
> bool
> FastISel::SelectOperator(User *I, unsigned Opcode) {
>   switch (Opcode) {
> @@ -618,6 +638,9 @@
>   case Instruction::Sub:
>     return SelectBinaryOp(I, ISD::SUB);
>   case Instruction::FSub:
> +    // FNeg is currently represented in LLVM IR as a special case  
> of FSub.
> +    if (BinaryOperator::isFNeg(I))
> +      return SelectFNeg(I);
>     return SelectBinaryOp(I, ISD::FSUB);
>   case Instruction::Mul:
>     return SelectBinaryOp(I, ISD::MUL);
>
> Added: llvm/trunk/test/CodeGen/X86/fast-isel-fneg.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/fast-isel-fneg.ll?rev=80963&view=auto
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- llvm/trunk/test/CodeGen/X86/fast-isel-fneg.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/fast-isel-fneg.ll Thu Sep  3  
> 17:53:57 2009
> @@ -0,0 +1,15 @@
> +; RUN: llvm-as < %s | llc -fast-isel -march=x86-64 | FileCheck %s
> +
> +; CHECK: doo:
> +; CHECK: xorpd
> +define double @doo(double %x) nounwind {
> +  %y = fsub double -0.0, %x
> +  ret double %y
> +}
> +
> +; CHECK: foo:
> +; CHECK: xorps
> +define float @foo(float %x) nounwind {
> +  %y = fsub float -0.0, %x
> +  ret float %y
> +}
>
>
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