On 7/10/2026 12:49 AM, Jeffrey Law wrote:
On 7/7/2026 3:39 PM, Daniel Barboza wrote:Canonicalize right shift non-equality comparisons with constants by turn them into a comparison with a left shifted constant. Assuming the generic format: (A >> CST1) CMP CST2 For CMP (<, >=) we'll compare A with CST2 left shifted by CST1: - (A >> CST1) < CST2 -> A < (CST2 << CST1) - (A >> CST1) >= CST2 -> A >= (CST2 << CST1) And for CMP (<=, >) we need to IOR the lower CST1 bits from the left shift: - (A >> CST1) <= CST2 -> A <= (CST2 << CST1) | mask - (A >> CST1) > CST2 -> A > (CST2 << CST1) | mask Given that the right hand side changes involves just constants, in the end we'll replace a rshift + cmp with just a cmp. Bootstrapped and regression tested in x86, aarch64 and RISC-V. PR tree-optimization/124808 gcc/ChangeLog: * match.pd(`(A >> CST1) CMP CST2`): New pattern. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/pr124808-2.c: New test. * gcc.dg/tree-ssa/pr124808.c: New test. --- Re-sending this patch since it got stalled since May 16th. Rebased and bootstrapped/regtested again with x86_64.Thanks for re-raising. This clearly got lost. This is OK for the trunk. And FTR I tested this across the various embedded targets too with no regressions.
Pushed. Thanks! Daniel
Jeff
