[PATCH] D153757: [RFC][TableGen][GlobalISel] Add Combiner Match Table Backend

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/utils/TableGen/GlobalISelMatchTable.cpp:883
 
-    for (const auto &InsnID : InsnIDs) {
-      // Reject the difficult cases until we have a more accurate check.
-      Table << MatchTable::Opcode("GIM_CheckIsSafeToFold")
-            << MatchTable::Comment("InsnID") << MatchTable::IntValue(InsnID)
-            << MatchTable::LineBreak;
-
-      // FIXME: Emit checks to determine it's _actually_ safe to fold and/or
-      //        account for unsafe cases.
-      //
-      //        Example:
-      //          MI1--> %0 = ...
-      //                 %1 = ... %0
-      //          MI0--> %2 = ... %0
-      //          It's not safe to erase MI1. We currently handle this by not
-      //          erasing %0 (even when it's dead).
-      //
-      //        Example:
-      //          MI1--> %0 = load volatile @a
-      //                 %1 = load volatile @a
-      //          MI0--> %2 = ... %0
-      //          It's not safe to sink %0's def past %1. We currently handle
-      //          this by rejecting all loads.
-      //
-      //        Example:
-      //          MI1--> %0 = load @a
-      //                 %1 = store @a
-      //          MI0--> %2 = ... %0
-      //          It's not safe to sink %0's def past %1. We currently handle
-      //          this by rejecting all loads.
-      //
-      //        Example:
-      //                   G_CONDBR %cond, @BB1
-      //                 BB0:
-      //          MI1-->   %0 = load @a
-      //                   G_BR @BB1
-      //                 BB1:
-      //          MI0-->   %2 = ... %0
-      //          It's not always safe to sink %0 across control flow. In this
-      //          case it may introduce a memory fault. We currentl handle this
-      //          by rejecting all loads.
+    // TODO: needed for combiner?
+    if (!Table.isCombiner()) {
----------------
Yes, I don't see how this would be avoidable


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D153757/new/

https://reviews.llvm.org/D153757