[llvm] r308265 - [CGP] Cleanup - remove redundant code in OptimizeMemoryInst. NFC

[Serguei Katkov via llvm-commits]

Author: skatkov
Date: Mon Jul 17 22:16:38 2017
New Revision: 308265

URL: http://llvm.org/viewvc/llvm-project?rev=308265&view=rev
Log:
[CGP] Cleanup - remove redundant code in OptimizeMemoryInst. NFC

optimizeMemoryInst contains a vector AddrModeInsts.
The only use of this vector is to check that all instructions are in the same
block as memory instruction. This check is guarded by PhiSeen flag,
so if we traversed through phi node then we do not need to keep information
in AddrModeInsts. AddModeInsts is set first time we found some addressing mode
and updated if we found new one later.
We can find next addressing mode only if we traverse phi node so all code
related to update of AddModeInsts can be safely removed.

Reviewers: loladiro, spatel, efriedma
Reviewed By: efriedma
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D35291

Modified:
    llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp

Modified: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp?rev=308265&r1=308264&r2=308265&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp Mon Jul 17 22:16:38 2017
@@ -4267,9 +4267,7 @@ bool CodeGenPrepare::optimizeMemoryInst(
   // Use a worklist to iteratively look through PHI nodes, and ensure that
   // the addressing mode obtained from the non-PHI roots of the graph
   // are equivalent.
-  Value *Consensus = nullptr;
-  unsigned NumUsesConsensus = 0;
-  bool IsNumUsesConsensusValid = false;
+  bool AddrModeFound = false;
   bool PhiSeen = false;
   SmallVector<Instruction*, 16> AddrModeInsts;
   ExtAddrMode AddrMode;
@@ -4282,7 +4280,7 @@ bool CodeGenPrepare::optimizeMemoryInst(
 
     // Break use-def graph loops.
     if (!Visited.insert(V).second) {
-      Consensus = nullptr;
+      AddrModeFound = false;
       break;
     }
 
@@ -4297,47 +4295,26 @@ bool CodeGenPrepare::optimizeMemoryInst(
     // For non-PHIs, determine the addressing mode being computed.  Note that
     // the result may differ depending on what other uses our candidate
     // addressing instructions might have.
-    SmallVector<Instruction*, 16> NewAddrModeInsts;
+    AddrModeInsts.clear();
     ExtAddrMode NewAddrMode = AddressingModeMatcher::Match(
-      V, AccessTy, AddrSpace, MemoryInst, NewAddrModeInsts, *TLI, *TRI,
-      InsertedInsts, PromotedInsts, TPT);
+        V, AccessTy, AddrSpace, MemoryInst, AddrModeInsts, *TLI, *TRI,
+        InsertedInsts, PromotedInsts, TPT);
 
-    // This check is broken into two cases with very similar code to avoid using
-    // getNumUses() as much as possible. Some values have a lot of uses, so
-    // calling getNumUses() unconditionally caused a significant compile-time
-    // regression.
-    if (!Consensus) {
-      Consensus = V;
+    if (!AddrModeFound) {
+      AddrModeFound = true;
       AddrMode = NewAddrMode;
-      AddrModeInsts = NewAddrModeInsts;
-      continue;
-    } else if (NewAddrMode == AddrMode) {
-      if (!IsNumUsesConsensusValid) {
-        NumUsesConsensus = Consensus->getNumUses();
-        IsNumUsesConsensusValid = true;
-      }
-
-      // Ensure that the obtained addressing mode is equivalent to that obtained
-      // for all other roots of the PHI traversal.  Also, when choosing one
-      // such root as representative, select the one with the most uses in order
-      // to keep the cost modeling heuristics in AddressingModeMatcher
-      // applicable.
-      unsigned NumUses = V->getNumUses();
-      if (NumUses > NumUsesConsensus) {
-        Consensus = V;
-        NumUsesConsensus = NumUses;
-        AddrModeInsts = NewAddrModeInsts;
-      }
       continue;
     }
+    if (NewAddrMode == AddrMode)
+      continue;
 
-    Consensus = nullptr;
+    AddrModeFound = false;
     break;
   }
 
   // If the addressing mode couldn't be determined, or if multiple different
   // ones were determined, bail out now.
-  if (!Consensus) {
+  if (!AddrModeFound) {
     TPT.rollback(LastKnownGood);
     return false;
   }