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Add a simple transformation. This allows us to compile one of the inner
loops in stepanov to this: .LBB_Z5test0PdS__2: # no_exit.1 fldl data(,%eax,8) fldl 24(%esp) faddp %st(1) fstl 24(%esp) incl %eax cmpl $2000, %eax fstpl 16(%esp) #FP_REG_KILL jl .LBB_Z5test0PdS__2 instead of this: .LBB_Z5test0PdS__2: # no_exit.1 fldl data(,%eax,8) fldl 24(%esp) faddp %st(1) fstl 24(%esp) incl %eax movl $data, %ecx movl %ecx, %edx addl $16000, %edx subl %ecx, %edx movl %edx, %ecx sarl $2, %ecx shrl $29, %ecx addl %ecx, %edx sarl $3, %edx cmpl %edx, %eax fstpl 16(%esp) #FP_REG_KILL jl .LBB_Z5test0PdS__2 The old instruction selector produced: .LBB_Z5test0PdS__2: # no_exit.1 fldl 24(%esp) faddl data(,%eax,8) fstl 24(%esp) movl %eax, %ecx incl %ecx incl %eax leal data+16000, %edx movl $data, %edi subl %edi, %edx movl %edx, %edi sarl $2, %edi shrl $29, %edi addl %edi, %edx sarl $3, %edx cmpl %edx, %ecx fstpl 16(%esp) #FP_REG_KILL jl .LBB_Z5test0PdS__2 # no_exit.1 Which is even worse! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19419 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -662,6 +662,14 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
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case ISD::XOR:
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case ISD::XOR:
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if (N1 == N2) return getConstant(0, VT); // xor X, Y -> 0
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if (N1 == N2) return getConstant(0, VT); // xor X, Y -> 0
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break;
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break;
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case ISD::SUB:
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if (N1.getOpcode() == ISD::ADD) {
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if (N1.Val->getOperand(0) == N2)
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return N1.Val->getOperand(1); // (A+B)-A == B
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if (N1.Val->getOperand(1) == N2)
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return N1.Val->getOperand(0); // (A+B)-B == A
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}
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break;
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}
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}
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SDNode *&N = BinaryOps[std::make_pair(Opcode, std::make_pair(N1, N2))];
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SDNode *&N = BinaryOps[std::make_pair(Opcode, std::make_pair(N1, N2))];
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