[RegisterCoalescer] Add new subtarget hook allowing targets to opt-out of coalescing.

[oota-llvm.git] / lib / CodeGen / RegisterCoalescer.cpp

diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp
index fd57983f0756f1d9079dec3f2f920b914d9a9c4e..0bda4c7998717a419428987128081d6fd4ea88cf 100644 (file)
--- a/lib/CodeGen/RegisterCoalescer.cpp
+++ b/lib/CodeGen/RegisterCoalescer.cpp
@@ -13,7 +13,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#define DEBUG_TYPE "regalloc"
 #include "RegisterCoalescer.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallSet.h"
@@ -42,6 +41,8 @@
 #include <cmath>
 using namespace llvm;
 
+#define DEBUG_TYPE "regalloc"
+
 STATISTIC(numJoins    , "Number of interval joins performed");
 STATISTIC(numCrossRCs , "Number of cross class joins performed");
 STATISTIC(numCommutes , "Number of instruction commuting performed");
@@ -240,9 +241,8 @@ static bool isSplitEdge(const MachineBasicBlock *MBB) {
   if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
     return false;
 
-  for (MachineBasicBlock::const_iterator MII = MBB->begin(), E = MBB->end();
-       MII != E; ++MII) {
-    if (!MII->isCopyLike() && !MII->isUnconditionalBranch())
+  for (const auto &MI : *MBB) {
+    if (!MI.isCopyLike() && !MI.isUnconditionalBranch())
       return false;
   }
   return true;
@@ -1037,6 +1037,23 @@ bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) {
     return false;
   }
 
+  if (CP.getNewRC()) {
+    const TargetSubtargetInfo &ST = TM->getSubtarget<TargetSubtargetInfo>();
+    auto SrcRC = MRI->getRegClass(CP.getSrcReg());
+    auto DstRC = MRI->getRegClass(CP.getDstReg());
+    unsigned SrcIdx = CP.getSrcIdx();
+    unsigned DstIdx = CP.getDstIdx();
+    if (CP.isFlipped()) {
+      std::swap(SrcIdx, DstIdx);
+      std::swap(SrcRC, DstRC);
+    }
+    if (!ST.shouldCoalesce(CopyMI, SrcRC, SrcIdx, DstRC, DstIdx,
+                            CP.getNewRC())) {
+      DEBUG(dbgs() << "\tSubtarget bailed on coalescing.\n");
+      return false;
+    }
+  }
+
   // Dead code elimination. This really should be handled by MachineDCE, but
   // sometimes dead copies slip through, and we can't generate invalid live
   // ranges.