https://godbolt.org/z/x3e349nEW
uint ConstSubVar(uint x)
{
return 32 - x;
}Program:ConstSubVar(uint):uint:this (FullOpts):
mov eax, esi
neg eax
add eax, 32
ret Should be:
Program:ConstSubVar(uint):uint:this (FullOpts):
mov eax, 32
sub eax, esi
ret We canonicalize into (cns1 + (-op2)) in morph:
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/* Check for "cns1 - op2" , we change it to "(cns1 + (-op2))" */ |
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noway_assert(op1); |
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if (op1->IsCnsIntOrI()) |
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{ |
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noway_assert(varTypeIsIntegralOrI(tree)); |
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// The type of the new GT_NEG node cannot just be op2->TypeGet(). |
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// Otherwise we may sign-extend incorrectly in cases where the GT_NEG |
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// node ends up feeding directly into a cast, for example in |
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// GT_CAST<ubyte>(GT_SUB(0, s_1.ubyte)) |
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if (op1->IsIntegralConst(0)) |
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{ |
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tree->ChangeOper(GT_NEG); |
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tree->gtType = genActualType(op2->TypeGet()); |
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tree->AsOp()->gtOp1 = op2; |
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tree->AsOp()->gtOp2 = nullptr; |
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DEBUG_DESTROY_NODE(op1); |
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return tree; |
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} |
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tree->AsOp()->gtOp2 = op2 = gtNewOperNode(GT_NEG, genActualType(op2->TypeGet()), op2); |
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fgMorphTreeDone(op2); |
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oper = GT_ADD; |
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tree->ChangeOper(oper); |
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goto CM_ADD_OP; |
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} |
https://godbolt.org/z/x3e349nEW
Should be:
We canonicalize into
(cns1 + (-op2))in morph:runtime/src/coreclr/jit/morph.cpp
Lines 7890 to 7920 in 209c66f