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JIT: block local constant propagation of handles when compiling with …
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…relocs (dotnet#1593)

This gives local constant prop the same behavior as value-number-based constant
prop; both now block handle propagation when the jit must generate relocs (R2R),
to ensure that handle references appear only in simple instruction forms like movs.

Prerequisite to dotnet#1309, which can enable such propagation.
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@AndyAyersMS
AndyAyersMS authored Jan 10, 2020
1 parent b77fc13 commit 3c0cea3
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Showing 3 changed files with 138 additions and 78 deletions.
203 changes: 130 additions & 73 deletions src/coreclr/src/jit/assertionprop.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2348,7 +2348,7 @@ AssertionIndex Compiler::optAssertionIsSubtype(GenTree* tree, GenTree* methodTab

//------------------------------------------------------------------------------
// optVNConstantPropOnTree: Substitutes tree with an evaluated constant while
// managing ref-counts and side-effects.
// managing side-effects.
//
// Arguments:
// block - The block containing the tree.
Expand All @@ -2374,10 +2374,6 @@ AssertionIndex Compiler::optAssertionIsSubtype(GenTree* tree, GenTree* methodTab
// the relop will evaluate to "true" or "false" statically, then the side-effects
// will be put into new statements, presuming the JTrue will be folded away.
//
// The ref-counts of any variables in the tree being replaced, will be
// appropriately decremented. The ref-counts of variables in the side-effect
// nodes will be retained.
//
GenTree* Compiler::optVNConstantPropOnTree(BasicBlock* block, GenTree* tree)
{
if (tree->OperGet() == GT_JTRUE)
Expand Down Expand Up @@ -2444,6 +2440,7 @@ GenTree* Compiler::optVNConstantPropOnTree(BasicBlock* block, GenTree* tree)
case TYP_LONG:
{
INT64 value = vnStore->ConstantValue<INT64>(vnCns);

#ifdef _TARGET_64BIT_
if (vnStore->IsVNHandle(vnCns))
{
Expand Down Expand Up @@ -2581,21 +2578,33 @@ GenTree* Compiler::optVNConstantPropOnTree(BasicBlock* block, GenTree* tree)
}
}

/*******************************************************************************************************
*
* Perform constant propagation on a tree given the "curAssertion" is true at the point of the "tree."
*
*/
GenTree* Compiler::optConstantAssertionProp(AssertionDsc* curAssertion,
GenTree* tree,
//------------------------------------------------------------------------------
// optConstantAssertionProp: Possibly substitute a constant for a local use
//
// Arguments:
// curAssertion - assertion to propagate
// tree - tree to possibly modify
// stmt - statement containing the tree
// index - index of this assertion in the assertion table
//
// Returns:
// Updated tree (may be the input tree, modified in place), or nullptr
//
// Notes:
// stmt may be nullptr during local assertion prop
//
GenTree* Compiler::optConstantAssertionProp(AssertionDsc* curAssertion,
GenTreeLclVarCommon* tree,
Statement* stmt DEBUGARG(AssertionIndex index))
{
unsigned lclNum = tree->AsLclVarCommon()->GetLclNum();
const unsigned lclNum = tree->GetLclNum();

#if FEATURE_ANYCSE
if (lclNumIsCSE(lclNum))
{
return nullptr;
}
#endif

GenTree* newTree = tree;

Expand All @@ -2614,6 +2623,14 @@ GenTree* Compiler::optConstantAssertionProp(AssertionDsc* curAssertion,
break;

case O2K_CONST_LONG:

#ifdef _TARGET_64BIT_
// Don't propagate handles if we need to report relocs.
if (opts.compReloc && ((curAssertion->op2.u1.iconFlags & GTF_ICON_HDL_MASK) != 0))
{
return nullptr;
}
#endif
if (newTree->gtType == TYP_LONG)
{
newTree->ChangeOperConst(GT_CNS_NATIVELONG);
Expand All @@ -2628,6 +2645,15 @@ GenTree* Compiler::optConstantAssertionProp(AssertionDsc* curAssertion,
break;

case O2K_CONST_INT:

#ifndef _TARGET_64BIT_
// Don't propagate handles if we need to report relocs.
if (opts.compReloc && ((curAssertion->op2.u1.iconFlags & GTF_ICON_HDL_MASK) != 0))
{
return nullptr;
}
#endif

if (curAssertion->op2.u1.iconFlags & GTF_ICON_HDL_MASK)
{
// Here we have to allocate a new 'large' node to replace the old one
Expand Down Expand Up @@ -2717,12 +2743,20 @@ GenTree* Compiler::optConstantAssertionProp(AssertionDsc* curAssertion,
return optAssertionProp_Update(newTree, tree, stmt);
}

/*******************************************************************************************************
*
* Called in the context of an existing copy assertion which makes an "==" assertion on "lclVar" and
* "copyVar." Before substituting "copyVar" for "lclVar", we make sure using "copy" doesn't widen access.
*
*/
//------------------------------------------------------------------------------
// optAssertionProp_LclVarTypeCheck: verify compatible types for copy prop
//
// Arguments:
// tree - tree to possibly modify
// lclVarDsc - local accessed by tree
// copyVarDsc - local to possibly copy prop into tree
//
// Returns:
// True if copy prop is safe.
//
// Notes:
// Before substituting copyVar for lclVar, make sure using copyVar doesn't widen access.
//
bool Compiler::optAssertionProp_LclVarTypeCheck(GenTree* tree, LclVarDsc* lclVarDsc, LclVarDsc* copyVarDsc)
{
/*
Expand Down Expand Up @@ -2769,22 +2803,31 @@ bool Compiler::optAssertionProp_LclVarTypeCheck(GenTree* tree, LclVarDsc* lclVar
return true;
}

/**********************************************************************************
*
* Perform copy assertion propagation when the lclNum and ssaNum of the "tree" match
* the "curAssertion."
*
*/
GenTree* Compiler::optCopyAssertionProp(AssertionDsc* curAssertion,
GenTree* tree,
//------------------------------------------------------------------------
// optCopyAssertionProp: copy prop use of one local with another
//
// Arguments:
// curAssertion - assertion triggering the possible copy
// tree - tree use to consider replacing
// stmt - statment containing the tree
// index - index of the assertion
//
// Returns:
// Updated tree, or nullptr
//
// Notes:
// stmt may be nullptr during local assertion prop
//
GenTree* Compiler::optCopyAssertionProp(AssertionDsc* curAssertion,
GenTreeLclVarCommon* tree,
Statement* stmt DEBUGARG(AssertionIndex index))
{
const AssertionDsc::AssertionDscOp1& op1 = curAssertion->op1;
const AssertionDsc::AssertionDscOp2& op2 = curAssertion->op2;

noway_assert(op1.lcl.lclNum != op2.lcl.lclNum);

unsigned lclNum = tree->AsLclVarCommon()->GetLclNum();
const unsigned lclNum = tree->GetLclNum();

// Make sure one of the lclNum of the assertion matches with that of the tree.
if (op1.lcl.lclNum != lclNum && op2.lcl.lclNum != lclNum)
Expand All @@ -2793,22 +2836,22 @@ GenTree* Compiler::optCopyAssertionProp(AssertionDsc* curAssertion,
}

// Extract the matching lclNum and ssaNum.
unsigned copyLclNum = (op1.lcl.lclNum == lclNum) ? op2.lcl.lclNum : op1.lcl.lclNum;
unsigned copySsaNum = BAD_VAR_NUM;
const unsigned copyLclNum = (op1.lcl.lclNum == lclNum) ? op2.lcl.lclNum : op1.lcl.lclNum;
unsigned copySsaNum = BAD_VAR_NUM;
if (!optLocalAssertionProp)
{
// Extract the ssaNum of the matching lclNum.
unsigned ssaNum = (op1.lcl.lclNum == lclNum) ? op1.lcl.ssaNum : op2.lcl.ssaNum;
copySsaNum = (op1.lcl.lclNum == lclNum) ? op2.lcl.ssaNum : op1.lcl.ssaNum;

if (ssaNum != tree->AsLclVarCommon()->GetSsaNum())
if (ssaNum != tree->GetSsaNum())
{
return nullptr;
}
}

LclVarDsc* copyVarDsc = &lvaTable[copyLclNum];
LclVarDsc* lclVarDsc = &lvaTable[lclNum];
LclVarDsc* const copyVarDsc = lvaGetDesc(copyLclNum);
LclVarDsc* const lclVarDsc = lvaGetDesc(lclNum);

// Make sure the types are compatible.
if (!optAssertionProp_LclVarTypeCheck(tree, lclVarDsc, copyVarDsc))
Expand All @@ -2822,8 +2865,8 @@ GenTree* Compiler::optCopyAssertionProp(AssertionDsc* curAssertion,
return nullptr;
}

tree->AsLclVarCommon()->SetSsaNum(copySsaNum);
tree->AsLclVarCommon()->SetLclNum(copyLclNum);
tree->SetSsaNum(copySsaNum);
tree->SetLclNum(copyLclNum);

#ifdef DEBUG
if (verbose)
Expand All @@ -2838,17 +2881,22 @@ GenTree* Compiler::optCopyAssertionProp(AssertionDsc* curAssertion,
return optAssertionProp_Update(tree, tree, stmt);
}

/*****************************************************************************
*
* Given a tree consisting of a just a LclVar and a set of available assertions
* we try to propagate an assertion and modify the LclVar tree if we can.
* We pass in the root of the tree via 'stmt', for local copy prop 'stmt' will
* be nullptr. Returns the modified tree, or nullptr if no assertion prop took place.
*/

GenTree* Compiler::optAssertionProp_LclVar(ASSERT_VALARG_TP assertions, GenTree* tree, Statement* stmt)
//------------------------------------------------------------------------
// optAssertionProp_LclVar: try and optimize a local var use via assertions
//
// Arguments:
// assertions - set of live assertions
// tree - local use to optimize
// stmt - statement containing the tree
//
// Returns:
// Updated tree, or nullptr
//
// Notes:
// stmt may be nullptr during local assertion prop
//
GenTree* Compiler::optAssertionProp_LclVar(ASSERT_VALARG_TP assertions, GenTreeLclVarCommon* tree, Statement* stmt)
{
assert(tree->gtOper == GT_LCL_VAR);
// If we have a var definition then bail or
// If this is the address of the var then it will have the GTF_DONT_CSE
// flag set and we don't want to to assertion prop on it.
Expand Down Expand Up @@ -2884,40 +2932,43 @@ GenTree* Compiler::optAssertionProp_LclVar(ASSERT_VALARG_TP assertions, GenTree*
{
// Perform copy assertion prop.
GenTree* newTree = optCopyAssertionProp(curAssertion, tree, stmt DEBUGARG(assertionIndex));
if (newTree == nullptr)
if (newTree != nullptr)
{
// Skip and try next assertion.
continue;
return newTree;
}
return newTree;
}

continue;
}
// Constant prop (for local assertion prop.)

// Constant prop.
//
// The case where the tree type could be different than the LclVar type is caused by
// gtFoldExpr, specifically the case of a cast, where the fold operation changes the type of the LclVar
// node. In such a case is not safe to perform the substitution since later on the JIT will assert mismatching
// types between trees.
else if (curAssertion->op1.lcl.lclNum == tree->AsLclVarCommon()->GetLclNum() &&
tree->gtType == lvaTable[tree->AsLclVarCommon()->GetLclNum()].lvType)
const unsigned lclNum = tree->GetLclNum();
if (curAssertion->op1.lcl.lclNum == lclNum)
{
// If local assertion prop just, perform constant prop.
if (optLocalAssertionProp)
LclVarDsc* const lclDsc = lvaGetDesc(lclNum);
// Verify types match
if (tree->TypeGet() == lclDsc->lvType)
{
return optConstantAssertionProp(curAssertion, tree, stmt DEBUGARG(assertionIndex));
}
// If global assertion, perform constant propagation only if the VN's match and the lcl is non-CSE.
else if (curAssertion->op1.vn == vnStore->VNConservativeNormalValue(tree->gtVNPair))
{
#if FEATURE_ANYCSE
// Don't perform constant prop for CSE LclVars
if (!lclNumIsCSE(tree->AsLclVarCommon()->GetLclNum()))
#endif
// If local assertion prop, just perform constant prop.
if (optLocalAssertionProp)
{
return optConstantAssertionProp(curAssertion, tree, stmt DEBUGARG(assertionIndex));
}

// If global assertion, perform constant propagation only if the VN's match.
if (curAssertion->op1.vn == vnStore->VNConservativeNormalValue(tree->gtVNPair))
{
return optConstantAssertionProp(curAssertion, tree, stmt DEBUGARG(assertionIndex));
}
}
}
}

return nullptr;
}

Expand Down Expand Up @@ -4003,21 +4054,27 @@ GenTree* Compiler::optAssertionProp_Update(GenTree* newTree, GenTree* tree, Stat
return newTree;
}

/*****************************************************************************
*
* Given a tree and a set of available assertions we try to propagate an
* assertion and modify 'tree' if we can. We pass in the root of the tree
* via 'stmt', for local copy prop 'stmt' will be nullptr.
*
* Returns the modified tree, or nullptr if no assertion prop took place.
*/

//------------------------------------------------------------------------
// optAssertionProp: try and optimize a tree via assertion propagation
//
// Arguments:
// assertions - set of live assertions
// tree - tree to possibly optimize
// stmt - statement containing the tree
// block - block containing the statement
//
// Returns:
// The modified tree, or nullptr if no assertion prop took place.
//
// Notes:
// stmt may be nullptr during local assertion prop
//
GenTree* Compiler::optAssertionProp(ASSERT_VALARG_TP assertions, GenTree* tree, Statement* stmt, BasicBlock* block)
{
switch (tree->gtOper)
{
case GT_LCL_VAR:
return optAssertionProp_LclVar(assertions, tree, stmt);
return optAssertionProp_LclVar(assertions, tree->AsLclVarCommon(), stmt);

case GT_OBJ:
case GT_BLK:
Expand Down
3 changes: 3 additions & 0 deletions src/coreclr/src/jit/codegencommon.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1375,6 +1375,9 @@ bool CodeGen::genCreateAddrMode(GenTree* addr,

if (op2->IsIntCnsFitsInI32() && (op2->gtType != TYP_REF) && FitsIn<INT32>(cns + op2->AsIntConCommon()->IconValue()))
{
// We should not be building address modes out of non-foldable constants
assert(op2->AsIntConCommon()->ImmedValCanBeFolded(compiler, addr->OperGet()));

/* We're adding a constant */

cns += op2->AsIntConCommon()->IconValue();
Expand Down
10 changes: 5 additions & 5 deletions src/coreclr/src/jit/compiler.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6761,16 +6761,16 @@ class Compiler

// Assertion prop for lcl var functions.
bool optAssertionProp_LclVarTypeCheck(GenTree* tree, LclVarDsc* lclVarDsc, LclVarDsc* copyVarDsc);
GenTree* optCopyAssertionProp(AssertionDsc* curAssertion,
GenTree* tree,
GenTree* optCopyAssertionProp(AssertionDsc* curAssertion,
GenTreeLclVarCommon* tree,
Statement* stmt DEBUGARG(AssertionIndex index));
GenTree* optConstantAssertionProp(AssertionDsc* curAssertion,
GenTree* tree,
GenTree* optConstantAssertionProp(AssertionDsc* curAssertion,
GenTreeLclVarCommon* tree,
Statement* stmt DEBUGARG(AssertionIndex index));

// Assertion propagation functions.
GenTree* optAssertionProp(ASSERT_VALARG_TP assertions, GenTree* tree, Statement* stmt, BasicBlock* block);
GenTree* optAssertionProp_LclVar(ASSERT_VALARG_TP assertions, GenTree* tree, Statement* stmt);
GenTree* optAssertionProp_LclVar(ASSERT_VALARG_TP assertions, GenTreeLclVarCommon* tree, Statement* stmt);
GenTree* optAssertionProp_Ind(ASSERT_VALARG_TP assertions, GenTree* tree, Statement* stmt);
GenTree* optAssertionProp_Cast(ASSERT_VALARG_TP assertions, GenTree* tree, Statement* stmt);
GenTree* optAssertionProp_Call(ASSERT_VALARG_TP assertions, GenTreeCall* call, Statement* stmt);
Expand Down

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