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Fold bitconv(bitconv(x)) -> x. We now compile this:

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void foo(double);
void bar(double X) { foo(X); }

to this:

bar:
        save -96, %o6, %o6
        or %g0, %i0, %o0
        or %g0, %i1, %o1
        call foo
        nop
        restore %g0, %g0, %g0
        retl
        nop

instead of this:

bar:
        save -112, %o6, %o6
        st %i1, [%i6+-4]
        st %i0, [%i6+-8]
        ldd [%i6+-8], %f0
        std %f0, [%i6+-16]
        ld [%i6+-12], %o1
        ld [%i6+-16], %o0
        call foo
        nop
        restore %g0, %g0, %g0
        retl
        nop

on V8.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24981 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-12-23 05:37:50 +00:00
parent 94683777ae
commit c8547d856d
2 changed files with 5 additions and 0 deletions
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3
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -1757,6 +1757,9 @@ SDOperand DAGCombiner::visitBIT_CONVERT(SDNode *N) {
if (Res.Val != N) return Res;
}
if (N0.getOpcode() == ISD::BIT_CONVERT) // conv(conv(x,t1),t2) -> conv(x,t2)
return DAG.getNode(ISD::BIT_CONVERT, VT, N0.getOperand(0));
return SDOperand();
}

2
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -916,6 +916,8 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
assert(MVT::getSizeInBits(VT)==MVT::getSizeInBits(Operand.getValueType()) &&
"Cannot BIT_CONVERT between two different types!");
if (VT == Operand.getValueType()) return Operand; // noop conversion.
if (OpOpcode == ISD::BIT_CONVERT) // bitconv(bitconv(x)) -> bitconv(x)
return getNode(ISD::BIT_CONVERT, VT, Operand.getOperand(0));
break;
case ISD::FNEG:
if (OpOpcode == ISD::FSUB) // -(X-Y) -> (Y-X)