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Add a simple transformation. This allows us to compile one of the inner

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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
This commit is contained in:
Chris Lattner 2005-01-09 20:09:57 +00:00
parent 250208587d
commit abd2182875
1 changed files with 8 additions and 0 deletions
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8
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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@ -662,6 +662,14 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
case ISD::XOR:
if (N1 == N2) return getConstant(0, VT); // xor X, Y -> 0
break;
case ISD::SUB:
if (N1.getOpcode() == ISD::ADD) {
if (N1.Val->getOperand(0) == N2)
return N1.Val->getOperand(1); // (A+B)-A == B
if (N1.Val->getOperand(1) == N2)
return N1.Val->getOperand(0); // (A+B)-B == A
}
break;
}
SDNode *&N = BinaryOps[std::make_pair(Opcode, std::make_pair(N1, N2))];