Pattern synonym performance
I introduce a pattern synonym in GHC
This causes five performance tests to fail https://gitlab.haskell.org/tweag/ghc/-/pipelines/38665.
T12227(normal) ghc/alloc 462602822.0 468124632.0 +1.2% BAD
T3064(normal) ghc/alloc 191629750.0 195597680.0 +2.1% BAD
T5030(normal) ghc/alloc 366141150.0 373936984.0 +2.1% BAD
T9872b(normal) ghc/alloc 2308378242.0 2336048448.0 +1.2% BAD
T9872d(normal) ghc/alloc 559641592.0 578809016.0 +3.4% BAD
I'm surprised that a relatively simple refactoring has this impact. Is there a bug? Could other pattern synonyms in GHC be causing a slowdown?
I cannot use the INLINE pragma on the pattern synonym yet, because it's available only from 9.2.
Original ticket: #18750.