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JIT: Add stress mode for skipping lowering conditional nodes to use CPU flags #103358

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JIT: Add stress mode for skipping lowering conditional nodes to use CPU flags #103358

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Add stress mode
amanasifkhalid Jun 12, 2024
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amanasifkhalid Jun 12, 2024
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amanasifkhalid Jun 13, 2024
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1 change: 1 addition & 0 deletions src/coreclr/jit/compiler.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10353,6 +10353,7 @@ class Compiler
STRESS_MODE(IF_CONVERSION_INNER_LOOPS) \
STRESS_MODE(POISON_IMPLICIT_BYREFS) \
STRESS_MODE(STORE_BLOCK_UNROLLING) \
STRESS_MODE(SKIP_COND_NODE_LOWERING) /* Don't lower conditions to use CPU flags */ \
STRESS_MODE(COUNT)

enum compStressArea
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8 changes: 8 additions & 0 deletions src/coreclr/jit/lower.cpp
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Expand Up @@ -4313,6 +4313,14 @@ bool Lowering::TryLowerConditionToFlagsNode(GenTree* parent, GenTree* condition,
DISPTREERANGE(BlockRange(), condition);
JITDUMP("\n");

#ifdef DEBUG
if (comp->compStressCompile(Compiler::STRESS_SKIP_COND_NODE_LOWERING, 50))
{
JITDUMP("JitStress: skip lowering attempt\n");
return false;
}
#endif // DEBUG
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50% of methods seems a bit high given the frequency of conditional branches.. maybe something like 10% is sufficient?

Nit: the ifdef is unnecessary, there is a release version of compStressCompile that always returns false (but feel free to leave it if you prefer to make it more visible that this is debug-only).

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Sounds good, I'll update it.


if (condition->OperIsCompare())
{
if (!IsInvariantInRange(condition, parent))
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