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optimizebools.cpp
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
/*XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XX XX
XX Optimizer XX
XX XX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
*/
#include "jitpch.h"
#ifdef _MSC_VER
#pragma hdrstop
#endif
/*****************************************************************************/
//-----------------------------------------------------------------------------
// OptTestInfo: Member of OptBoolsDsc struct used to test if a GT_JTRUE or GT_RETURN node
// is a boolean comparison
//
struct OptTestInfo
{
Statement* testStmt; // Last statement of the basic block
GenTree* testTree; // The root node of the testStmt (GT_JTRUE or GT_RETURN).
GenTree* compTree; // The compare node (i.e. GT_EQ or GT_NE node) of the testTree
bool isBool; // If the compTree is boolean expression
};
//-----------------------------------------------------------------------------
// OptBoolsDsc: Descriptor used for Boolean Optimization
//
class OptBoolsDsc
{
public:
OptBoolsDsc(BasicBlock* b1, BasicBlock* b2, Compiler* comp)
{
m_b1 = b1;
m_b2 = b2;
m_b3 = nullptr;
m_comp = comp;
}
private:
BasicBlock* m_b1; // The first basic block with the BBJ_COND conditional jump type
BasicBlock* m_b2; // The next basic block of m_b1. Either BBJ_COND or BBJ_RETURN type
BasicBlock* m_b3; // m_b1->bbTarget. Null if m_b2 is not a return block.
Compiler* m_comp; // The pointer to the Compiler instance
OptTestInfo m_testInfo1; // The first test info
OptTestInfo m_testInfo2; // The second test info
GenTree* m_t3; // The root node of the first statement of m_b3
GenTree* m_c1; // The first operand of m_testInfo1.compTree
GenTree* m_c2; // The first operand of m_testInfo2.compTree
bool m_sameTarget; // if m_b1 and m_b2 jumps to the same destination
genTreeOps m_foldOp; // The fold operator (e.g., GT_AND or GT_OR)
var_types m_foldType; // The type of the folded tree
genTreeOps m_cmpOp; // The comparison operator (e.g., GT_EQ or GT_NE)
public:
bool optOptimizeBoolsCondBlock();
bool optOptimizeCompareChainCondBlock();
bool optOptimizeRangeTests();
bool optOptimizeBoolsReturnBlock(BasicBlock* b3);
#ifdef DEBUG
void optOptimizeBoolsGcStress();
#endif
private:
Statement* optOptimizeBoolsChkBlkCond();
GenTree* optIsBoolComp(OptTestInfo* pOptTest);
bool optOptimizeBoolsChkTypeCostCond();
void optOptimizeBoolsUpdateTrees();
bool FindCompareChain(GenTree* condition, bool* isTestCondition);
};
//-----------------------------------------------------------------------------
// optOptimizeBoolsCondBlock: Optimize boolean when bbKind of both m_b1 and m_b2 are BBJ_COND
//
// Returns:
// true if boolean optimization is done and m_b1 and m_b2 are folded into m_b1, else false.
//
// Notes:
// m_b1 and m_b2 are set on entry.
//
// Case 1: if b1.bbTarget == b2.bbTarget, it transforms
// B1 : brtrue(t1, Bx)
// B2 : brtrue(t2, Bx)
// B3 :
// to
// B1 : brtrue(t1|t2, BX)
// B3 :
//
// For example, (x == 0 && y == 0 && z == 0) generates
// B1: GT_JTRUE (BBJ_COND), jump to B4
// B2: GT_JTRUE (BBJ_COND), jump to B4
// B3: GT_RETURN (BBJ_RETURN)
// B4: GT_RETURN (BBJ_RETURN)
// and B1 and B2 are folded into B1:
// B1: GT_JTRUE (BBJ_COND), jump to B4
// B3: GT_RETURN (BBJ_RETURN)
// B4: GT_RETURN (BBJ_RETURN)
//
// Case 2: if B2->FalseTargetIs(B1.bbTarget), it transforms
// B1 : brtrue(t1, B3)
// B2 : brtrue(t2, Bx)
// B3 :
// to
// B1 : brtrue((!t1) && t2, Bx)
// B3 :
//
bool OptBoolsDsc::optOptimizeBoolsCondBlock()
{
assert(m_b1 != nullptr && m_b2 != nullptr && m_b3 == nullptr);
// Check if m_b1 and m_b2 jump to the same target and get back pointers to m_testInfo1 and t2 tree nodes
m_t3 = nullptr;
// Check if m_b1 and m_b2 have the same bbTarget
if (m_b1->TrueTargetIs(m_b2->GetTrueTarget()))
{
// Given the following sequence of blocks :
// B1: brtrue(t1, BX)
// B2: brtrue(t2, BX)
// B3:
// we will try to fold it to :
// B1: brtrue(t1|t2, BX)
// B3:
m_sameTarget = true;
}
else if (m_b2->FalseTargetIs(m_b1->GetTrueTarget()))
{
// Given the following sequence of blocks :
// B1: brtrue(t1, B3)
// B2: brtrue(t2, BX)
// B3:
// we will try to fold it to :
// B1: brtrue((!t1)&&t2, BX)
// B3:
m_sameTarget = false;
}
else
{
return false;
}
Statement* const s1 = optOptimizeBoolsChkBlkCond();
if (s1 == nullptr)
{
return false;
}
// Find the branch conditions of m_b1 and m_b2
m_c1 = optIsBoolComp(&m_testInfo1);
if (m_c1 == nullptr)
{
return false;
}
m_c2 = optIsBoolComp(&m_testInfo2);
if (m_c2 == nullptr)
{
return false;
}
// Find the type and cost conditions of m_testInfo1 and m_testInfo2
if (!optOptimizeBoolsChkTypeCostCond())
{
return false;
}
// Get the fold operator and the comparison operator
genTreeOps foldOp;
genTreeOps cmpOp;
var_types foldType = genActualType(m_c1);
if (varTypeIsGC(foldType))
{
foldType = TYP_I_IMPL;
}
assert(m_testInfo1.compTree->OperIs(GT_EQ, GT_NE, GT_LT, GT_GT, GT_GE, GT_LE));
if (m_sameTarget)
{
if (m_c1->gtOper == GT_LCL_VAR && m_c2->gtOper == GT_LCL_VAR &&
m_c1->AsLclVarCommon()->GetLclNum() == m_c2->AsLclVarCommon()->GetLclNum())
{
if ((m_testInfo1.compTree->gtOper == GT_LT && m_testInfo2.compTree->gtOper == GT_EQ) ||
(m_testInfo1.compTree->gtOper == GT_EQ && m_testInfo2.compTree->gtOper == GT_LT))
{
// Case: t1:c1<0 t2:c1==0
// So we will branch to BX if c1<=0
//
// Case: t1:c1==0 t2:c1<0
// So we will branch to BX if c1<=0
cmpOp = GT_LE;
}
else if ((m_testInfo1.compTree->gtOper == GT_GT && m_testInfo2.compTree->gtOper == GT_EQ) ||
(m_testInfo1.compTree->gtOper == GT_EQ && m_testInfo2.compTree->gtOper == GT_GT))
{
// Case: t1:c1>0 t2:c1==0
// So we will branch to BX if c1>=0
//
// Case: t1:c1==0 t2:c1>0
// So we will branch to BX if c1>=0
cmpOp = GT_GE;
}
else
{
return false;
}
foldOp = GT_NONE;
}
else if (m_testInfo1.compTree->gtOper == GT_EQ && m_testInfo2.compTree->gtOper == GT_EQ)
{
// t1:c1==0 t2:c2==0 ==> Branch to BX if either value is 0
// So we will branch to BX if (c1&c2)==0
foldOp = GT_AND;
cmpOp = GT_EQ;
}
else if (m_testInfo1.compTree->gtOper == GT_LT && m_testInfo2.compTree->gtOper == GT_LT &&
(!m_testInfo1.testTree->AsOp()->gtOp1->IsUnsigned() &&
!m_testInfo2.testTree->AsOp()->gtOp1->IsUnsigned()))
{
// t1:c1<0 t2:c2<0 ==> Branch to BX if either value < 0
// So we will branch to BX if (c1|c2)<0
foldOp = GT_OR;
cmpOp = GT_LT;
}
else if (m_testInfo1.compTree->gtOper == GT_NE && m_testInfo2.compTree->gtOper == GT_NE)
{
// t1:c1!=0 t2:c2!=0 ==> Branch to BX if either value is non-0
// So we will branch to BX if (c1|c2)!=0
foldOp = GT_OR;
cmpOp = GT_NE;
}
else
{
return false;
}
}
else
{
if (m_c1->gtOper == GT_LCL_VAR && m_c2->gtOper == GT_LCL_VAR &&
m_c1->AsLclVarCommon()->GetLclNum() == m_c2->AsLclVarCommon()->GetLclNum())
{
if ((m_testInfo1.compTree->gtOper == GT_LT && m_testInfo2.compTree->gtOper == GT_NE) ||
(m_testInfo1.compTree->gtOper == GT_EQ && m_testInfo2.compTree->gtOper == GT_GE))
{
// Case: t1:c1<0 t2:c1!=0
// So we will branch to BX if c1>0
//
// Case: t1:c1==0 t2:c1>=0
// So we will branch to BX if c1>0
cmpOp = GT_GT;
}
else if ((m_testInfo1.compTree->gtOper == GT_GT && m_testInfo2.compTree->gtOper == GT_NE) ||
(m_testInfo1.compTree->gtOper == GT_EQ && m_testInfo2.compTree->gtOper == GT_LE))
{
// Case: t1:c1>0 t2:c1!=0
// So we will branch to BX if c1<0
//
// Case: t1:c1==0 t2:c1<=0
// So we will branch to BX if c1<0
cmpOp = GT_LT;
}
else
{
return false;
}
foldOp = GT_NONE;
}
else if (m_testInfo1.compTree->gtOper == GT_EQ && m_testInfo2.compTree->gtOper == GT_NE)
{
// t1:c1==0 t2:c2!=0 ==> Branch to BX if both values are non-0
// So we will branch to BX if (c1&c2)!=0
foldOp = GT_AND;
cmpOp = GT_NE;
}
else if (m_testInfo1.compTree->gtOper == GT_LT && m_testInfo2.compTree->gtOper == GT_GE &&
(!m_testInfo1.testTree->AsOp()->gtOp1->IsUnsigned() &&
!m_testInfo2.testTree->AsOp()->gtOp1->IsUnsigned()))
{
// t1:c1<0 t2:c2>=0 ==> Branch to BX if both values >= 0
// So we will branch to BX if (c1|c2)>=0
foldOp = GT_OR;
cmpOp = GT_GE;
}
else if (m_testInfo1.compTree->gtOper == GT_NE && m_testInfo2.compTree->gtOper == GT_EQ)
{
// t1:c1!=0 t2:c2==0 ==> Branch to BX if both values are 0
// So we will branch to BX if (c1|c2)==0
foldOp = GT_OR;
cmpOp = GT_EQ;
}
else
{
return false;
}
}
// Anding requires both values to be 0 or 1
if ((foldOp == GT_AND) && (!m_testInfo1.isBool || !m_testInfo2.isBool))
{
return false;
}
//
// Now update the trees
//
m_foldOp = foldOp;
m_foldType = foldType;
m_cmpOp = cmpOp;
optOptimizeBoolsUpdateTrees();
#ifdef DEBUG
if (m_comp->verbose)
{
printf("Folded %sboolean conditions of " FMT_BB " and " FMT_BB " to :\n", m_c2->OperIsLeaf() ? "" : "non-leaf ",
m_b1->bbNum, m_b2->bbNum);
m_comp->gtDispStmt(s1);
printf("\n");
}
#endif
// Return true to continue the bool optimization for the rest of the BB chain
return true;
}
//-----------------------------------------------------------------------------
// FindCompareChain: Check if the given condition is a compare chain.
//
// Arguments:
// condition: Condition to check.
// isTestCondition: Returns true if condition is but is not a compare chain.
//
// Returns:
// true if chain optimization is a compare chain.
//
// Assumptions:
// m_b1 and m_b2 are set on entry.
//
bool OptBoolsDsc::FindCompareChain(GenTree* condition, bool* isTestCondition)
{
GenTree* condOp1 = condition->gtGetOp1();
GenTree* condOp2 = condition->gtGetOp2();
*isTestCondition = false;
if (condition->OperIs(GT_EQ, GT_NE) && condOp2->IsIntegralConst())
{
ssize_t condOp2Value = condOp2->AsIntCon()->IconValue();
if (condOp2Value == 0)
{
// Found a EQ/NE(...,0). Does it contain a compare chain (ie - conditions that have
// previously been combined by optOptimizeCompareChainCondBlock) or is it a test condition
// that will be optimised to cbz/cbnz during lowering?
if (condOp1->OperIs(GT_AND, GT_OR))
{
// Check that the second operand of AND/OR ends with a compare operation, as this will be
// the condition the new link in the chain will connect with.
if (condOp1->gtGetOp2()->OperIsCmpCompare() && varTypeIsIntegralOrI(condOp1->gtGetOp2()->gtGetOp1()))
{
return true;
}
}
*isTestCondition = true;
}
else if (condOp1->OperIs(GT_AND) && isPow2(static_cast<target_size_t>(condOp2Value)) &&
condOp1->gtGetOp2()->IsIntegralConst(condOp2Value))
{
// Found a EQ/NE(AND(...,n),n) which will be optimized to tbz/tbnz during lowering.
*isTestCondition = true;
}
}
return false;
}
//------------------------------------------------------------------------------
// GetIntersection: Given two ranges, return true if they intersect and form a closed range.
// Examples:
// >10 and <=20 -> [11,20]
// >10 and >100 -> false
// <10 and >10 -> false
//
// Arguments:
// type - The type of the compare nodes.
// cmp1 - The first compare node.
// cmp2 - The second compare node.
// cns1 - The constant value of the first compare node (always RHS).
// cns2 - The constant value of the second compare node (always RHS).
// pRangeStart - [OUT] The start of the intersection range (inclusive).
// pRangeEnd - [OUT] The end of the intersection range (inclusive).
//
// Returns:
// true if the ranges intersect and form a closed range.
//
static bool GetIntersection(var_types type,
genTreeOps cmp1,
genTreeOps cmp2,
ssize_t cns1,
ssize_t cns2,
ssize_t* pRangeStart,
ssize_t* pRangeEnd)
{
if ((cns1 < 0) || (cns2 < 0))
{
// We don't yet support negative ranges.
return false;
}
// Convert to a canonical form with GT_GE or GT_LE (inclusive).
auto normalize = [](genTreeOps* cmp, ssize_t* cns) {
if (*cmp == GT_GT)
{
// "X > cns" -> "X >= cns + 1"
*cns = *cns + 1;
*cmp = GT_GE;
}
if (*cmp == GT_LT)
{
// "X < cns" -> "X <= cns - 1"
*cns = *cns - 1;
*cmp = GT_LE;
}
// whether these overflow or not is checked below.
};
normalize(&cmp1, &cns1);
normalize(&cmp2, &cns2);
if (cmp1 == cmp2)
{
// Ranges have the same direction (we don't yet support that yet).
return false;
}
if (cmp1 == GT_GE)
{
*pRangeStart = cns1;
*pRangeEnd = cns2;
}
else
{
assert(cmp1 == GT_LE);
*pRangeStart = cns2;
*pRangeEnd = cns1;
}
if ((*pRangeStart >= *pRangeEnd) || (*pRangeStart < 0) || (*pRangeEnd < 0) || !FitsIn(type, *pRangeStart) ||
!FitsIn(type, *pRangeEnd))
{
// TODO: If ranges don't intersect we might be able to fold the condition to true/false.
// Also, check again if any of the ranges are negative (in case of overflow after normalization)
// and fits into the given type.
return false;
}
return true;
}
//------------------------------------------------------------------------------
// IsConstantRangeTest: Does the given compare node represent a constant range test? E.g.
// "X relop CNS" or "CNS relop X" where relop is [<, <=, >, >=]
//
// Arguments:
// tree - compare node
// varNode - [OUT] this will be set to the variable part of the constant range test
// cnsNode - [OUT] this will be set to the constant part of the constant range test
// cmp - [OUT] this will be set to a normalized compare operator so that the constant
// is always on the right hand side of the compare.
//
// Returns:
// true if the compare node represents a constant range test.
//
bool IsConstantRangeTest(GenTreeOp* tree, GenTree** varNode, GenTreeIntCon** cnsNode, genTreeOps* cmp)
{
if (tree->OperIs(GT_LE, GT_LT, GT_GE, GT_GT) && !tree->IsUnsigned())
{
GenTree* op1 = tree->gtGetOp1();
GenTree* op2 = tree->gtGetOp2();
if (varTypeIsIntegral(op1) && varTypeIsIntegral(op2) && op1->TypeIs(op2->TypeGet()))
{
if (op2->IsCnsIntOrI())
{
// X relop CNS
*varNode = op1;
*cnsNode = op2->AsIntCon();
*cmp = tree->OperGet();
return true;
}
if (op1->IsCnsIntOrI())
{
// CNS relop X
*varNode = op2;
*cnsNode = op1->AsIntCon();
// Normalize to "X relop CNS"
*cmp = GenTree::SwapRelop(tree->OperGet());
return true;
}
}
}
return false;
}
//------------------------------------------------------------------------------
// FoldRangeTests: Given two compare nodes (cmp1 && cmp2) where cmp1 is X >= 0
// and cmp2 is X < NN (NeverNegative), try to fold the range test into a single
// X u< NN (unsigned) compare node.
//
// Arguments:
// compiler - compiler instance
// cmp1 - first compare node
// cmp1IsReversed - true if cmp1 is in fact reversed
// cmp2 - second compare node
// cmp2IsReversed - true if cmp2 is in fact reversed
//
// Returns:
// true if cmp1 now represents the folded range check and cmp2 can be removed.
//
bool FoldNeverNegativeRangeTest(
Compiler* comp, GenTreeOp* cmp1, bool cmp1IsReversed, GenTreeOp* cmp2, bool cmp2IsReversed)
{
GenTree* var1Node;
GenTreeIntCon* cns1Node;
genTreeOps cmp1Op;
// First cmp has to be "X >= 0" (or "0 <= X")
// TODO: handle "X < NN && X >= 0" (where the 2nd comparison is the lower bound)
// It seems to be a rare case, so we don't handle it for now.
if (!IsConstantRangeTest(cmp1, &var1Node, &cns1Node, &cmp1Op))
{
return false;
}
// Now, reverse the comparison if necessary depending on cmp1IsReversed and cmp2IsReversed
// so we'll get a canonical form of "X >= 0 && X </<= NN"
cmp1Op = cmp1IsReversed ? GenTree::ReverseRelop(cmp1Op) : cmp1Op;
genTreeOps cmp2Op = cmp2IsReversed ? GenTree::ReverseRelop(cmp2->OperGet()) : cmp2->OperGet();
if ((cmp1Op != GT_GE) || (!cns1Node->IsIntegralConst(0)))
{
// Lower bound check has to be "X >= 0".
// We already re-ordered the comparison so that the constant is always on the right side.
return false;
}
// Upper bound check has to be "X relop NN" or "NN relop X" (NN = NeverNegative)
// We allow var1Node to be a GT_COMMA node, so we need to call gtEffectiveVal() to get the actual variable
// since it's guaranteed to be evaluated first.
GenTree* upperBound;
if (cmp2->gtGetOp1()->OperIs(GT_LCL_VAR, GT_LCL_FLD) &&
GenTree::Compare(var1Node->gtEffectiveVal(), cmp2->gtGetOp1()))
{
// "X relop NN"
upperBound = cmp2->gtGetOp2();
}
else if (cmp2->gtGetOp2()->OperIs(GT_LCL_VAR, GT_LCL_FLD) &&
GenTree::Compare(var1Node->gtEffectiveVal(), cmp2->gtGetOp2()))
{
// "NN relop X"
upperBound = cmp2->gtGetOp1();
// Normalize to "X relop NN"
cmp2Op = GenTree::SwapRelop(cmp2Op);
}
else
{
return false;
}
// Check that our upper bound is known to be never negative (e.g. GT_ARR_LENGTH or Span.Length, etc.)
if (!upperBound->IsNeverNegative(comp) || !upperBound->TypeIs(var1Node->TypeGet()))
{
return false;
}
if ((upperBound->gtFlags & GTF_SIDE_EFFECT) != 0)
{
// We can't fold "X >= 0 && X < NN" to "X u< NN" if NN has side effects.
return false;
}
if ((cmp2Op != GT_LT) && (cmp2Op != GT_LE))
{
// Upper bound check has to be "X < NN" or "X <= NN" (normalized form).
return false;
}
cmp1->gtOp1 = var1Node;
cmp1->gtOp2 = upperBound;
cmp1->SetOper(cmp2IsReversed ? GenTree::ReverseRelop(cmp2Op) : cmp2Op);
cmp1->SetUnsigned();
return true;
}
//------------------------------------------------------------------------------
// FoldRangeTests: Given two compare nodes (cmp1 && cmp2) that represent a range check,
// fold them into a single compare node if possible, e.g.:
// 1) "X >= 10 && X <= 100" -> "(X - 10) u<= 90"
// 2) "X >= 0 && X <= 100" -> "X u<= 100"
// where 'u' stands for unsigned comparison. cmp1 is used as the target node for folding.
// It's also guaranteed to be first in the execution order (so can allow some side effects).
//
// Arguments:
// compiler - compiler instance
// cmp1 - first compare node
// cmp1IsReversed - true if cmp1 is in fact reversed
// cmp2 - second compare node
// cmp2IsReversed - true if cmp2 is in fact reversed
//
// Returns:
// true if cmp1 now represents the folded range check and cmp2 can be removed.
//
bool FoldRangeTests(Compiler* comp, GenTreeOp* cmp1, bool cmp1IsReversed, GenTreeOp* cmp2, bool cmp2IsReversed)
{
GenTree* var1Node;
GenTree* var2Node;
GenTreeIntCon* cns1Node;
GenTreeIntCon* cns2Node;
genTreeOps cmp1Op;
genTreeOps cmp2Op;
// Make sure both conditions are constant range checks, e.g. "X > CNS"
if (!IsConstantRangeTest(cmp1, &var1Node, &cns1Node, &cmp1Op) ||
!IsConstantRangeTest(cmp2, &var2Node, &cns2Node, &cmp2Op))
{
// Give FoldNeverNegativeRangeTest a try if both conditions are not constant range checks.
return FoldNeverNegativeRangeTest(comp, cmp1, cmp1IsReversed, cmp2, cmp2IsReversed);
}
// Reverse the comparisons if necessary so we'll get a canonical form "cond1 == true && cond2 == true" -> InRange.
cmp1Op = cmp1IsReversed ? GenTree::ReverseRelop(cmp1Op) : cmp1Op;
cmp2Op = cmp2IsReversed ? GenTree::ReverseRelop(cmp2Op) : cmp2Op;
// Make sure variables are the same:
if (!var2Node->OperIs(GT_LCL_VAR) || !GenTree::Compare(var1Node->gtEffectiveVal(), var2Node))
{
// Variables don't match in two conditions
// We use gtEffectiveVal() for the first block's variable to ignore COMMAs, e.g.
//
// m_b1:
// * JTRUE void
// \--* LT int
// +--* COMMA int
// | +--* STORE_LCL_VAR int V03 cse0
// | | \--* CAST int <- ushort <- int
// | | \--* LCL_VAR int V01 arg1
// | \--* LCL_VAR int V03 cse0
// \--* CNS_INT int 97
//
// m_b2:
// * JTRUE void
// \--* GT int
// +--* LCL_VAR int V03 cse0
// \--* CNS_INT int 122
//
// For the m_b2 we require the variable to be just a local with no side-effects (hence, no statements)
return false;
}
ssize_t rangeStart;
ssize_t rangeEnd;
if (!GetIntersection(var1Node->TypeGet(), cmp1Op, cmp2Op, cns1Node->IconValue(), cns2Node->IconValue(), &rangeStart,
&rangeEnd))
{
// The range we test via two conditions is not a closed range
// TODO: We should support overlapped ranges here, e.g. "X > 10 && x > 100" -> "X > 100"
return false;
}
assert(rangeStart < rangeEnd);
if (rangeStart == 0)
{
// We don't need to subtract anything, it's already 0-based
cmp1->gtOp1 = var1Node;
}
else
{
// We need to subtract the rangeStartIncl from the variable to make the range start from 0
cmp1->gtOp1 = comp->gtNewOperNode(GT_SUB, var1Node->TypeGet(), var1Node,
comp->gtNewIconNode(rangeStart, var1Node->TypeGet()));
}
cmp1->gtOp2->BashToConst(rangeEnd - rangeStart, var1Node->TypeGet());
cmp1->SetOper(cmp2IsReversed ? GT_GT : GT_LE);
cmp1->SetUnsigned();
return true;
}
//------------------------------------------------------------------------------
// optOptimizeRangeTests : Optimize two conditional blocks representing a constant range test.
// E.g. "X >= 10 && X <= 100" is optimized to "(X - 10) <= 90".
//
// Return Value:
// True if m_b1 and m_b2 are merged.
//
bool OptBoolsDsc::optOptimizeRangeTests()
{
// At this point we have two consecutive conditional blocks (BBJ_COND): m_b1 and m_b2
assert((m_b1 != nullptr) && (m_b2 != nullptr) && (m_b3 == nullptr));
assert(m_b1->KindIs(BBJ_COND) && m_b2->KindIs(BBJ_COND) && m_b1->FalseTargetIs(m_b2));
if (m_b2->isRunRarely())
{
// We don't want to make the first comparison to be slightly slower
// if the 2nd one is rarely executed.
return false;
}
if (!BasicBlock::sameEHRegion(m_b1, m_b2) || m_b2->HasFlag(BBF_DONT_REMOVE))
{
// Conditions aren't in the same EH region or m_b2 can't be removed
return false;
}
if (m_b1->TrueTargetIs(m_b1) || m_b1->TrueTargetIs(m_b2) || m_b2->TrueTargetIs(m_b2) || m_b2->TrueTargetIs(m_b1))
{
// Ignoring weird cases like a condition jumping to itself or when JumpDest == Next
return false;
}
// We're interested in just two shapes for e.g. "X > 10 && X < 100" range test:
//
BasicBlock* notInRangeBb = m_b1->GetTrueTarget();
BasicBlock* inRangeBb;
if (m_b2->TrueTargetIs(notInRangeBb))
{
// Shape 1: both conditions jump to NotInRange
//
// if (X <= 10)
// goto NotInRange;
//
// if (X >= 100)
// goto NotInRange
//
// InRange:
// ...
inRangeBb = m_b2->GetFalseTarget();
}
else if (m_b2->FalseTargetIs(notInRangeBb))
{
// Shape 2: 2nd block jumps to InRange
//
// if (X <= 10)
// goto NotInRange;
//
// if (X > 100)
// goto InRange
//
// NotInRange:
// ...
inRangeBb = m_b2->GetTrueTarget();
}
else
{
// Unknown shape
return false;
}
if (!m_b2->hasSingleStmt() || (m_b2->GetUniquePred(m_comp) != m_b1))
{
// The 2nd block has to be single-statement to avoid side-effects between the two conditions.
// Also, make sure m_b2 has no other predecessors.
return false;
}
// m_b1 and m_b2 are both BBJ_COND blocks with GT_JTRUE(cmp) root nodes
GenTreeOp* cmp1 = m_b1->lastStmt()->GetRootNode()->gtGetOp1()->AsOp();
GenTreeOp* cmp2 = m_b2->lastStmt()->GetRootNode()->gtGetOp1()->AsOp();
// cmp1 is always reversed (see shape1 and shape2 above)
const bool cmp1IsReversed = true;
// cmp2 can be either reversed or not
const bool cmp2IsReversed = m_b2->TrueTargetIs(notInRangeBb);
if (!FoldRangeTests(m_comp, cmp1, cmp1IsReversed, cmp2, cmp2IsReversed))
{
return false;
}
// Re-direct firstBlock to jump to inRangeBb
m_comp->fgAddRefPred(inRangeBb, m_b1);
if (!cmp2IsReversed)
{
m_b1->SetTrueTarget(inRangeBb);
m_b1->SetFalseTarget(notInRangeBb);
}
else
{
m_b1->SetFalseTarget(inRangeBb);
}
// Remove the 2nd condition block as we no longer need it
m_comp->fgRemoveRefPred(m_b2, m_b1);
m_comp->fgRemoveBlock(m_b2, true);
Statement* stmt = m_b1->lastStmt();
m_comp->gtSetStmtInfo(stmt);
m_comp->fgSetStmtSeq(stmt);
m_comp->gtUpdateStmtSideEffects(stmt);
return true;
}
//-----------------------------------------------------------------------------
// optOptimizeCompareChainCondBlock: Create a chain when both m_b1 and m_b2 are BBJ_COND.
//
// Returns:
// true if chain optimization is done and m_b1 and m_b2 are folded into m_b1, else false.
//
// Assumptions:
// m_b1 and m_b2 are set on entry.
//
// Notes:
//
// This aims to reduced the number of conditional jumps by joining cases when multiple
// conditions gate the execution of a block.
//
// Example 1:
// If ( a > b || c == d) { x = y; }
//
// Will be represented in IR as:
//
// ------------ BB01 -> BB03 (cond), succs={BB02,BB03}
// * JTRUE (GT a,b)
//
// ------------ BB02 -> BB04 (cond), preds={BB01} succs={BB03,BB04}
// * JTRUE (NE c,d)
//
// ------------ BB03, preds={BB01, BB02} succs={BB04}
// * STORE_LCL_VAR<x>(y)
//
// These operands will be combined into a single AND in the first block (with the first
// condition inverted), wrapped by the test condition (NE(...,0)). Giving:
//
// ------------ BB01 -> BB03 (cond), succs={BB03,BB04}
// * JTRUE (NE (AND (LE a,b), (NE c,d)), 0)
//
// ------------ BB03, preds={BB01} succs={BB04}
// * STORE_LCL_VAR<x>(y)
//
//
// Example 2:
// If ( a > b && c == d) { x = y; } else { x = z; }
//
// Here the && conditions are connected via an OR. After the pass:
//
// ------------ BB01 -> BB03 (cond), succs={BB03,BB04}
// * JTRUE (NE (OR (LE a,b), (NE c,d)), 0)
//
// ------------ BB03, preds={BB01} succs={BB05}
// * STORE_LCL_VAR<x>(y)
//
// ------------ BB04, preds={BB01} succs={BB05}
// * STORE_LCL_VAR<x>(z)
//
//
// Example 3:
// If ( a > b || c == d || e < f ) { x = y; }
// The first pass of the optimization will combine two of the conditions. The
// second pass will then combine remaining condition the earlier chain.
//
// ------------ BB01 -> BB03 (cond), succs={BB03,BB04}
// * JTRUE (NE (OR ((NE (OR (NE c,d), (GE e,f)), 0), (LE a,b))), 0)
//
// ------------ BB03, preds={BB01} succs={BB04}
// * STORE_LCL_VAR<x>(y)
//
//
// This optimization means that every condition within the IF statement is always evaluated,
// as opposed to stopping at the first positive match.
// Theoretically there is no maximum limit on the size of the generated chain. Therefore cost
// checking is used to limit the maximum number of conditions that can be chained together.
//
bool OptBoolsDsc::optOptimizeCompareChainCondBlock()
{
assert((m_b1 != nullptr) && (m_b2 != nullptr) && (m_b3 == nullptr));
m_t3 = nullptr;
bool foundEndOfOrConditions = false;
if (m_b1->FalseTargetIs(m_b2) && m_b2->FalseTargetIs(m_b1->GetTrueTarget()))
{
// Found the end of two (or more) conditions being ORed together.
// The final condition has been inverted.
foundEndOfOrConditions = true;
}
else if (m_b1->FalseTargetIs(m_b2) && m_b1->TrueTargetIs(m_b2->GetTrueTarget()))
{
// Found two conditions connected together.
}
else
{
return false;
}
Statement* const s1 = optOptimizeBoolsChkBlkCond();
if (s1 == nullptr)
{
return false;
}
Statement* s2 = m_b2->firstStmt();
assert(m_testInfo1.testTree->OperIs(GT_JTRUE));
GenTree* cond1 = m_testInfo1.testTree->gtGetOp1();
assert(m_testInfo2.testTree->OperIs(GT_JTRUE));
GenTree* cond2 = m_testInfo2.testTree->gtGetOp1();
// Ensure both conditions are suitable.
if (!cond1->OperIsCompare() || !cond2->OperIsCompare())
{
return false;
}
// Ensure there are no additional side effects.
if ((cond1->gtFlags & (GTF_SIDE_EFFECT | GTF_ORDER_SIDEEFF)) != 0 ||
(cond2->gtFlags & (GTF_SIDE_EFFECT | GTF_ORDER_SIDEEFF)) != 0)
{
return false;
}
// Integer compares only for now (until support for Arm64 fccmp instruction is added)
if (varTypeIsFloating(cond1->gtGetOp1()) || varTypeIsFloating(cond2->gtGetOp1()))
{
return false;
}
// Check for previously optimized compare chains.
bool op1IsTestCond;
bool op2IsTestCond;
bool op1IsCondChain = FindCompareChain(cond1, &op1IsTestCond);
bool op2IsCondChain = FindCompareChain(cond2, &op2IsTestCond);
// Avoid cases where optimizations in lowering will produce better code than optimizing here.
if (op1IsTestCond || op2IsTestCond)
{
return false;
}
// Combining conditions means that all conditions are always fully evaluated.
// Put a limit on the max size that can be combined.
if (!m_comp->compStressCompile(Compiler::STRESS_OPT_BOOLS_COMPARE_CHAIN_COST, 25))
{
int op1Cost = cond1->GetCostEx();
int op2Cost = cond2->GetCostEx();
// The cost of combing three simple conditions is 32.
int maxOp1Cost = op1IsCondChain ? 31 : 7;
int maxOp2Cost = op2IsCondChain ? 31 : 7;
// Cost to allow for chain size of three.
if (op1Cost > maxOp1Cost || op2Cost > maxOp2Cost)
{
JITDUMP("Skipping CompareChainCond that will evaluate conditions unconditionally at costs %d,%d\n", op1Cost,
op2Cost);
return false;
}
}
// Remove the first JTRUE statement.
constexpr bool isUnlink = true;
m_comp->fgRemoveStmt(m_b1, s1 DEBUGARG(isUnlink));
// Invert the condition.
if (foundEndOfOrConditions)
{
GenTree* revCond = m_comp->gtReverseCond(cond1);
assert(cond1 == revCond); // Ensure `gtReverseCond` did not create a new node.
}
// Join the two conditions together
genTreeOps chainedOper = foundEndOfOrConditions ? GT_AND : GT_OR;
GenTree* chainedConditions = m_comp->gtNewOperNode(chainedOper, TYP_INT, cond1, cond2);
cond1->gtFlags &= ~GTF_RELOP_JMP_USED;