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bugc: rename phi incoming blocks when block merging folds a block - #320
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At
-O3, aforloop that carries a local across iterations compiled to bytecode that reverted. Levels 0–2 were correct. A loop that calls an internal function to update an accumulator is one common way to hit it, but the call is incidental: level 2 inlines it, and a plainacc = acc + iloop fails the same way.The cause is in the block-merging step, which only runs at level 3. It folds the loop's update block into the body block and rewrites predecessor sets and jump targets, but it left the loop header's phi operands keyed by the deleted block. The header's phis then had no operand for the back edge, and the generated bytecode reverted.
The step now renames the key in every phi's
sources(andsourcesDebug) from the merged block to the block it merged into.Behavioral tests in
evmgen/behavioral.test.tsrun a loop-carried local and an internal call in a loop at every optimization level and check the stored result.