[ARITH] Simplify nested if_then_else when constant is appearing in then_expr #16227
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This change looks reasonable, to have parallel optimizations between the true and false branches. I have one request for the unit test, to remove unnecessary parts of the unit test, and can approve it after that.
I'm a bit confused as to the pre-existing implementation, though. Since this is a simplification of an expression, I would have expected this to be part of the overall Analyzer class, with any context provided by Analyzer::Bind or With<ConstraintContext>. The IRMutatorWithAnalyzer shouldn't be required for any simplifications.
For the long-term, we should probably move the IterMapSimplifyWithContext out of IRMutatorWithAnalyzer, and into an object held by arith::Analyzer (i.e. an IterMapSimplifier). That way, it would receive context from the usual Bind and With<ConstraintContext> mechanisms, wouldn't need to re-parse the predicate for each simplification, and would be compatible with other sub-analyzers.
| class TestNestedIfElimination(BaseBeforeAfter): | ||
| def before(a: T.Buffer((2, 8), "int32"), b: T.Buffer((2, 8), "int32")): | ||
| for i0, j0 in T.grid(2, 8): | ||
| with T.block("P"): |
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Does the test case depend on the BlockNode being present? If not, we should remove it. (Removing the with T.block, T.axis.remap, T.reads, and T.writes lines, then using i0 and j0 directly.)
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When constant is appearing in the else_expr, Simplifier pass is able to simplify the nested if_then_else expression and eliminate the redundant if_then_else. But, when constant is appearing in the then_expr, it is unable to simplify the nested if_then_else statements.
The changes in the PR will address the above problem.