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JIT: extend redundant relop to handle side effects #61275

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Merged
AndyAyersMS merged 2 commits into from
Nov 9, 2021
Merged

JIT: extend redundant relop to handle side effects #61275

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a954ea6
JIT: extend redundant relop to handle side effects
AndyAyersMS Nov 5, 2021
abc92ea
verify exception set
AndyAyersMS Nov 8, 2021
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verify exception set
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@AndyAyersMS
AndyAyersMS committed Nov 8, 2021
commit abc92ea96f89162bf1a70c3a6fa05174a3832751
29 changes: 23 additions & 6 deletions src/coreclr/jit/redundantbranchopts.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -794,6 +794,14 @@ bool Compiler::optRedundantRelop(BasicBlock* const block)
return false;
}

// If there's just one statement, bail.
//
if (stmt == block->firstStmt())
{
JITDUMP(" -- no, no prior stmt\n");
return false;
}

GenTree* const jumpTree = stmt->GetRootNode();

if (!jumpTree->OperIs(GT_JTRUE))
Expand Down Expand Up @@ -828,13 +836,9 @@ bool Compiler::optRedundantRelop(BasicBlock* const block)
return false;
}

// If there's just one statement, bail.
// Save off the jump tree's liberal exceptional VN.
//
if (stmt == block->firstStmt())
{
JITDUMP(" -- no, no prior stmt\n");
return false;
}
const ValueNum treeExcVN = vnStore->VNExceptionSet(tree->GetVN(VNK_Liberal));

JITDUMP("\noptRedundantRelop in " FMT_BB "; jump tree is\n", block->bbNum);
DISPTREE(jumpTree);
Expand Down Expand Up @@ -1002,6 +1006,19 @@ bool Compiler::optRedundantRelop(BasicBlock* const block)

JITDUMP(" -- prev tree has relop with %s liberal VN\n", ValueNumStore::VNRelationString(vnRelationMatch));

// If the jump tree VN has exceptions, verify that the RHS tree has a superset.
//
if (treeExcVN != vnStore->VNForEmptyExcSet())
{
const ValueNum prevTreeExcVN = vnStore->VNExceptionSet(prevTreeRHS->GetVN(VNK_Liberal));

if (!vnStore->VNExcIsSubset(prevTreeExcVN, treeExcVN))
{
JITDUMP(" -- prev tree does not anticipate all jump tree exceptions\n");
break;
}
}

// See if we can safely move a copy of prevTreeRHS later, to replace tree.
// We can, if none of its lcls are killed.
//
Expand Down