diff options
Diffstat (limited to 'llvm/lib/CodeGen/RegisterPressure.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/RegisterPressure.cpp | 19 |
1 files changed, 12 insertions, 7 deletions
diff --git a/llvm/lib/CodeGen/RegisterPressure.cpp b/llvm/lib/CodeGen/RegisterPressure.cpp index 36341039acf..667783e2952 100644 --- a/llvm/lib/CodeGen/RegisterPressure.cpp +++ b/llvm/lib/CodeGen/RegisterPressure.cpp @@ -750,9 +750,11 @@ void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) { /// /// This assumes that the current LiveOut set is sufficient. /// -/// FIXME: This is expensive for an on-the-fly query. We need to cache the -/// result per-SUnit with enough information to adjust for the current -/// scheduling position. But this works as a proof of concept. +/// This is expensive for an on-the-fly query because it calls +/// bumpUpwardPressure to recompute the pressure sets based on current +/// liveness. This mainly exists to verify correctness, e.g. with +/// -verify-misched. getUpwardPressureDelta is the fast version of this query +/// that uses the per-SUnit cache of the PressureDiff. void RegPressureTracker:: getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff, RegPressureDelta &Delta, @@ -809,10 +811,8 @@ getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff, #endif } -/// This is a prototype of the fast version of querying register pressure that -/// does not directly depend on current liveness. It's still slow because we -/// recompute pressure change on-the-fly. This implementation only exists to -/// prove correctness. +/// This is the fast version of querying register pressure that does not +/// directly depend on current liveness. /// /// @param Delta captures information needed for heuristics. /// @@ -950,6 +950,11 @@ void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) { /// register units of that pressure set introduced by this instruction. /// /// This assumes that the current LiveIn set is sufficient. +/// +/// This is expensive for an on-the-fly query because it calls +/// bumpDownwardPressure to recompute the pressure sets based on current +/// liveness. We don't yet have a fast version of downward pressure tracking +/// analagous to getUpwardPressureDelta. void RegPressureTracker:: getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta, ArrayRef<PressureChange> CriticalPSets, |
