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[arm64] JIT: X % 2 == 0 -> X & 1 == 0 #62399

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merged 4 commits into from
Dec 7, 2021
Merged

[arm64] JIT: X % 2 == 0 -> X & 1 == 0 #62399

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894b6b2
Handle X % 2 == 0 on arm64
EgorBo Dec 4, 2021
bbccf1e
remove fgUpdateConstTreeValueNumber
EgorBo Dec 4, 2021
6e97a3f
Move (a % c) ==/!= 0 transformation to pre-order
EgorBo Dec 4, 2021
1c301b5
Address feedback
EgorBo Dec 4, 2021
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102 changes: 30 additions & 72 deletions src/coreclr/jit/morph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11447,6 +11447,36 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac)
{
return fgMorphTree(optimizedTree);
}

// Pattern-matching optimization:
// (a % c) ==/!= 0
// for power-of-2 constant `c`
// =>
// a & (c - 1) ==/!= 0
// For integer `a`, even if negative.
if (opts.OptimizationEnabled() && !optValnumCSE_phase)
{
assert(tree->OperIs(GT_EQ, GT_NE));
if (op1->OperIs(GT_MOD) && varTypeIsIntegral(op1) && op2->IsIntegralConst(0))
{
GenTree* op1op2 = op1->AsOp()->gtOp2;
if (op1op2->IsCnsIntOrI())
{
ssize_t modValue = op1op2->AsIntCon()->IconValue();
if (isPow2(modValue))
{
JITDUMP("\nTransforming:\n");
DISPTREE(tree);

op1->SetOper(GT_AND); // Change % => &
op1op2->AsIntConCommon()->SetIconValue(modValue - 1); // Change c => c - 1
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JITDUMP("\ninto:\n");
DISPTREE(tree);
}
}
}
}
}

FALLTHROUGH;
Expand Down Expand Up @@ -13355,78 +13385,6 @@ GenTree* Compiler::fgOptimizeEqualityComparisonWithConst(GenTreeOp* cmp)
GenTree* op1 = cmp->gtGetOp1();
GenTreeIntConCommon* op2 = cmp->gtGetOp2()->AsIntConCommon();

// Pattern-matching optimization:
// (a % c) ==/!= 0
// for power-of-2 constant `c`
// =>
// a & (c - 1) ==/!= 0
// For integer `a`, even if negative.
if (opts.OptimizationEnabled())
{
if (op1->OperIs(GT_MOD) && varTypeIsIntegral(op1) && op2->IsIntegralConst(0))
{
GenTree* op1op2 = op1->AsOp()->gtOp2;
if (op1op2->IsCnsIntOrI())
{
ssize_t modValue = op1op2->AsIntCon()->IconValue();
if (isPow2(modValue))
{
JITDUMP("\nTransforming:\n");
DISPTREE(cmp);

op1->SetOper(GT_AND); // Change % => &
op1op2->AsIntConCommon()->SetIconValue(modValue - 1); // Change c => c - 1
fgUpdateConstTreeValueNumber(op1op2);

JITDUMP("\ninto:\n");
DISPTREE(cmp);
}
}
}
}

// Now let's do the same but for a more complicated input:
// (X - ((X / C1) << C2)) != 0
// where C1 is a power-of-two number and 1 << C2 equals C3.
// It is especially important for ARM64 where "X % POT_CNS ==/!= 0" is transformed to this pattern early
if (fgGlobalMorph && op2->IsIntegralConst(0) && op1->OperIs(GT_SUB) && !op1->gtOverflow() && varTypeIsIntegral(op1))
{
GenTree* lsh = op1->gtGetOp2();
if (lsh->OperIs(GT_LSH) && lsh->gtGetOp2()->IsCnsIntOrI() && lsh->gtGetOp1()->OperIs(GT_DIV))
{
GenTreeOp* div = lsh->gtGetOp1()->AsOp();
const ssize_t c1 = lsh->gtGetOp2()->AsIntCon()->IconValue();
if (div->OperIs(GT_DIV) && div->gtGetOp2()->IsCnsIntOrI())
{
const ssize_t c2 = div->gtGetOp2()->AsIntCon()->IconValue();

// Same X is used twice, in the second case it can be a COMMA
if (op1->gtGetOp1()->OperIsLeaf() &&
GenTree::Compare(op1->gtGetOp1(), div->gtGetOp1()->gtEffectiveVal(), false))
{
if ((c2 > 1) && isPow2(c2) && ((1ULL << (size_t)c1) == (size_t)c2))
{
JITDUMP("\nTransforming:\n");
DISPTREE(cmp);

DEBUG_DESTROY_NODE(lsh->gtGetOp2());
DEBUG_DESTROY_NODE(op1->gtGetOp1());
DEBUG_DESTROY_NODE(lsh);
DEBUG_DESTROY_NODE(op1);

// Transform to "X & (C2 - 1) ==/!= 0"
div->SetOper(GT_AND);
div->gtGetOp2()->AsIntConCommon()->SetIconValue(c2 - 1);
cmp->gtOp1 = op1 = div;

JITDUMP("\ninto:\n");
DISPTREE(cmp);
}
}
}
}
}

// Check for "(expr +/- icon1) ==/!= (non-zero-icon2)".
if (op2->IsCnsIntOrI() && (op2->IconValue() != 0))
{
Expand Down