[PATCH] D52370: [MachineCopyPropagation] Rework how we manage RegMask clobbers

[Justin Bogner via Phabricator via llvm-commits]

bogner created this revision.
bogner added a reviewer: MatzeB.
Herald added subscribers: llvm-commits, mcrosier.

Instead of updating the CopyTracker's maps each time we come across a
RegMask, defer checking for this kind of interference until we're
actually trying to propagate a copy. This avoids the need to
repeatedly iterate over maps in the cases where we don't end up doing
any work.

This is a slight compile time improvement for MachineCopyPropagation
as is, but it also enables a much bigger improvement that I'll follow
up with soon.


Repository:
  rL LLVM

https://reviews.llvm.org/D52370

Files:
  lib/CodeGen/MachineCopyPropagation.cpp


Index: lib/CodeGen/MachineCopyPropagation.cpp
===================================================================
--- lib/CodeGen/MachineCopyPropagation.cpp
+++ lib/CodeGen/MachineCopyPropagation.cpp
@@ -99,33 +99,6 @@
     }
   }
 
-  /// Remove any entry in the tracker's copy maps that is marked clobbered in \p
-  /// RegMask. The map will typically have a lot fewer entries than the regmask
-  /// clobbers, so this is more efficient than iterating the clobbered registers
-  /// and calling ClobberRegister() on them.
-  void removeClobberedRegs(const MachineOperand &RegMask,
-                           const TargetRegisterInfo &TRI) {
-    auto RemoveFromMap = [&RegMask](Reg2MIMap &Map) {
-      for (Reg2MIMap::iterator I = Map.begin(), E = Map.end(), Next; I != E;
-           I = Next) {
-        Next = std::next(I);
-        if (RegMask.clobbersPhysReg(I->first))
-          Map.erase(I);
-      }
-    };
-    RemoveFromMap(AvailCopyMap);
-    RemoveFromMap(CopyMap);
-
-    for (SourceMap::iterator I = SrcMap.begin(), E = SrcMap.end(), Next; I != E;
-         I = Next) {
-      Next = std::next(I);
-      if (RegMask.clobbersPhysReg(I->first)) {
-        markRegsUnavailable(I->second, TRI);
-        SrcMap.erase(I);
-      }
-    }
-  }
-
   /// Clobber a single register, removing it from the tracker's copy maps.
   void clobberRegister(unsigned Reg, const TargetRegisterInfo &TRI) {
     for (MCRegAliasIterator AI(Reg, &TRI, true); AI.isValid(); ++AI) {
@@ -287,6 +260,19 @@
   if (!isNopCopy(*PrevCopy, Src, Def, TRI))
     return false;
 
+  for (auto I = PrevCopy->getIterator(), E = Copy.getIterator(); I != E; ++I) {
+    const MachineOperand *RegMask = nullptr;
+    for (const MachineOperand &MO : I->operands())
+      if (MO.isRegMask()) {
+        RegMask = &MO;
+        break;
+      }
+    if (!RegMask)
+      continue;
+    if (RegMask->clobbersPhysReg(Src) || RegMask->clobbersPhysReg(Def))
+      return false;
+  }
+
   LLVM_DEBUG(dbgs() << "MCP: copy is a NOP, removing: "; Copy.dump());
 
   // Copy was redundantly redefining either Src or Def. Remove earlier kill
@@ -593,8 +579,6 @@
         Changed = true;
         ++NumDeletes;
       }
-
-      Tracker.removeClobberedRegs(*RegMask, *TRI);
     }
 
     // Any previous copy definition or reading the Defs is no longer available.


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