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Use BBF_NO_CSE_IN more widely #104922

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Use BBF_NO_CSE_IN more widely #104922

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59 changes: 39 additions & 20 deletions src/coreclr/jit/redundantbranchopts.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1628,6 +1628,31 @@ bool Compiler::optJumpThreadCore(JumpThreadInfo& jti)
//
JITDUMP("Optimizing via jump threading\n");

bool setNoCseIn = false;

// If this is a phi-based threading, and the block we're bypassing has
// a memory phi, mark the successor blocks with BBF_NO_CSE_IN so we can
// block unsound CSE propagation.
//
if (jti.m_isPhiBased)
{
for (MemoryKind memoryKind : allMemoryKinds())
{
if ((memoryKind == ByrefExposed) && byrefStatesMatchGcHeapStates)
{
continue;
}

if (jti.m_block->bbMemorySsaPhiFunc[memoryKind] != nullptr)
{
JITDUMP(FMT_BB " has %s memory phi; will be marking blocks with BBF_NO_CSE_IN\n", jti.m_block->bbNum,
memoryKindNames[memoryKind]);
setNoCseIn = true;
break;
}
}
}

// Now reroute the flow from the predecessors.
// If this pred is in the set that will reuse block, do nothing.
// Else revise pred to branch directly to the appropriate successor of block.
Expand All @@ -1638,6 +1663,11 @@ bool Compiler::optJumpThreadCore(JumpThreadInfo& jti)
//
if (BlockSetOps::IsMember(this, jti.m_ambiguousPreds, predBlock->bbNum))
{
if (setNoCseIn && !jti.m_block->HasFlag(BBF_NO_CSE_IN))
{
JITDUMP(FMT_BB " => BBF_NO_CSE_IN\n", jti.m_block->bbNum);
jti.m_block->SetFlags(BBF_NO_CSE_IN);
}
continue;
}

Expand All @@ -1652,6 +1682,12 @@ bool Compiler::optJumpThreadCore(JumpThreadInfo& jti)
predBlock->bbNum, jti.m_block->bbNum, predBlock->bbNum, jti.m_trueTarget->bbNum);

fgReplaceJumpTarget(predBlock, jti.m_block, jti.m_trueTarget);

if (setNoCseIn && !jti.m_trueTarget->HasFlag(BBF_NO_CSE_IN))
{
JITDUMP(FMT_BB " => BBF_NO_CSE_IN\n", jti.m_trueTarget->bbNum);
jti.m_trueTarget->SetFlags(BBF_NO_CSE_IN);
}
}
else
{
Expand All @@ -1660,28 +1696,11 @@ bool Compiler::optJumpThreadCore(JumpThreadInfo& jti)
predBlock->bbNum, jti.m_block->bbNum, predBlock->bbNum, jti.m_falseTarget->bbNum);

fgReplaceJumpTarget(predBlock, jti.m_block, jti.m_falseTarget);
}
}

// If this is a phi-based threading, and the block we're bypassing has
// a memory phi, mark the block with BBF_NO_CSE_IN so we can block CSE propagation
// into the block.
//
if (jti.m_isPhiBased)
{
for (MemoryKind memoryKind : allMemoryKinds())
{
if ((memoryKind == ByrefExposed) && byrefStatesMatchGcHeapStates)
{
continue;
}

if (jti.m_block->bbMemorySsaPhiFunc[memoryKind] != nullptr)
if (setNoCseIn && !jti.m_falseTarget->HasFlag(BBF_NO_CSE_IN))
{
JITDUMP(FMT_BB " has %s memory phi; marking as BBF_NO_CSE_IN\n", jti.m_block->bbNum,
memoryKindNames[memoryKind]);
jti.m_block->SetFlags(BBF_NO_CSE_IN);
break;
JITDUMP(FMT_BB " => BBF_NO_CSE_IN\n", jti.m_falseTarget->bbNum);
jti.m_falseTarget->SetFlags(BBF_NO_CSE_IN);
}
}
}
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