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Change bbAssertionOut if BBJ_COND was folded in morph #125222

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Merged
EgorBo merged 4 commits into from
Mar 6, 2026
Merged

Change bbAssertionOut if BBJ_COND was folded in morph #125222

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99ea5e6
JIT: Fix stale bbAssertionOut when BBJ_COND is folded during Global AP
Mar 5, 2026
3106a12
Change bbAssertionOut if BBJ_COND was folded in morph
Mar 5, 2026
4bcd294
disable for LocalAP
EgorBo Mar 5, 2026
4d2b333
Update assertionprop.cpp
EgorBo Mar 5, 2026
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48 changes: 48 additions & 0 deletions src/coreclr/jit/assertionprop.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6343,9 +6343,57 @@ PhaseStatus Compiler::optAssertionPropMain()
printf("\n");
}
#endif
// Record BBJ_COND state before morphing so we can fix up
// assertion out sets if morph changes the block's edges.
bool wasCond = block->KindIs(BBJ_COND);
BasicBlock* trueBb = wasCond ? block->GetTrueTarget() : nullptr;
BasicBlock* falseBb = wasCond ? block->GetFalseTarget() : nullptr;

// Re-morph the statement.
fgMorphBlockStmt(block, stmt DEBUGARG("optAssertionPropMain"));
madeChanges = true;

// Fix up assertion out sets if morphing changed the block's edges in a way
// that affects the semantics of the assertions.
//
if (wasCond && !optLocalAssertionProp)
{
if (!block->KindIs(BBJ_COND))
{
// NOTE: if trueBb == falseBb then we don't know how assertions may change
// so we take the conservative path in that case.
//
if ((block->GetUniqueSucc() == trueBb) && (trueBb != falseBb))
{
// BBJ_COND was folded (e.g. to BBJ_ALWAYS).
// Fix up bbAssertionOut to match the retained edge.
//
BitVecOps::Assign(apTraits, block->bbAssertionOut, bbJtrueAssertionOut[block->bbNum]);
}
else if ((block->GetUniqueSucc() == falseBb) && (trueBb != falseBb))
{
// bbAssertionOut already has the false-edge assertions.
}
else
{
// Converted to something unexpected (e.g. BBJ_SWITCH) — conservatively
// just propagate the IN assertions, which is better than losing all assertions.
//
BitVecOps::Assign(apTraits, block->bbAssertionOut, block->bbAssertionIn);
// We can also quickly walk over the trees and accumulate more assertions if needed.
// NOTE: this is not valid for LocalAP as assertions may die in the middle of the block
}
}
else if ((block->GetTrueTarget() != trueBb) || (block->GetFalseTarget() != falseBb))
{
// Conservatively clear assertions if edges changed in any way that we don't expect.
// We still can be smart here and handle e.g. edge flip.
//
BitVecOps::Assign(apTraits, block->bbAssertionOut, block->bbAssertionIn);
BitVecOps::Assign(apTraits, bbJtrueAssertionOut[block->bbNum], block->bbAssertionIn);
// NOTE: this is not valid for LocalAP as assertions may die in the middle of the block
}
}
}

// Check if propagation removed statements starting from current stmt.
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