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JIT: don't merge assertions from orphaned pred blocks #131471

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Merged
AndyAyersMS merged 1 commit into from
Jul 28, 2026
+11 −1
Merged

JIT: don't merge assertions from orphaned pred blocks #131471

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12 changes: 11 additions & 1 deletion src/coreclr/jit/rangecheck.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1742,7 +1742,17 @@ void RangeCheck::MergeAssertion(BasicBlock* block, GenTree* op, Range* pRange DE
if (op->OperIs(GT_PHI_ARG))
{
const BasicBlock* pred = op->AsPhiArg()->gtPredBB;
assertions = m_compiler->optGetEdgeAssertions(block, pred);

// Flow edits (e.g. RBO jump threading) can orphan a block without removing it or
// updating phis that name it as gtPredBB. Assertions on an edge out of an unreachable
// block don't hold, so don't merge them. Symmetric to the guard in
// Compiler::optVisitReachingAssertions (compiler.hpp).
if ((pred->bbPreds == nullptr) && (pred != m_compiler->fgFirstBB) && !m_compiler->bbIsHandlerBeg(pred))
{
return;
}

assertions = m_compiler->optGetEdgeAssertions(block, pred);
if (!BitVecOps::MayBeUninit(assertions))
{
JITDUMP("Merge assertions created by " FMT_BB " for " FMT_BB "\n", pred->bbNum, block->bbNum);
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