[PATCH] D16890: Fix PR25339: ARM Constant Island

[Weiming Zhao via llvm-commits]

weimingz created this revision.
weimingz added a subscriber: llvm-commits.
weimingz set the repository for this revision to rL LLVM.
Herald added subscribers: rengolin, aemerson.

Currently, the ARM Constant Island may not converge (or not converge quickly).
This patch let it move to the closest water after the user if it doesn't converge after 15 iterations.

Repository:
  rL LLVM

http://reviews.llvm.org/D16890

Files:
  lib/Target/ARM/ARMConstantIslandPass.cpp

Index: lib/Target/ARM/ARMConstantIslandPass.cpp
===================================================================
--- lib/Target/ARM/ARMConstantIslandPass.cpp
+++ lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -292,11 +292,11 @@
     bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
     unsigned getCombinedIndex(const MachineInstr *CPEMI);
     int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
-    bool findAvailableWater(CPUser&U, unsigned UserOffset,
-                            water_iterator &WaterIter);
+    bool findAvailableWater(CPUser &U, unsigned UserOffset,
+                            water_iterator &WaterIter, bool IgnoreGrowth);
     void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
                         MachineBasicBlock *&NewMBB);
-    bool handleConstantPoolUser(unsigned CPUserIndex);
+    bool handleConstantPoolUser(unsigned CPUserIndex, bool IgnoreGrowth);
     void removeDeadCPEMI(MachineInstr *CPEMI);
     bool removeUnusedCPEntries();
     bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
@@ -456,7 +456,7 @@
     DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
     bool CPChange = false;
     for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
-      CPChange |= handleConstantPoolUser(i);
+      CPChange |= handleConstantPoolUser(i, NoCPIters >= 15 /*Ignore Growth*/);
     if (CPChange && ++NoCPIters > 30)
       report_fatal_error("Constant Island pass failed to converge!");
     DEBUG(dumpBBs());
@@ -1293,7 +1293,8 @@
 /// move to a lower address, so search backward from the end of the list and
 /// prefer the first water that is in range.
 bool ARMConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
-                                      water_iterator &WaterIter) {
+                                            water_iterator &WaterIter,
+                                            bool IgnoreGrowth) {
   if (WaterList.empty())
     return false;
 
@@ -1309,6 +1310,8 @@
     // should be relatively uncommon and when it does happen, we want to be
     // sure to take advantage of it for all the CPEs near that block, so that
     // we don't insert more branches than necessary.
+    // When IgnoreGrowth is true, we try to find the lowerest address after (or
+    // equal to) user MI's BB no matter of padding growth.
     unsigned Growth;
     if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
         (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
@@ -1319,9 +1322,10 @@
       WaterIter = IP;
       DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
                    << " Growth=" << Growth << '\n');
-
+      if (IgnoreGrowth && WaterBB == U.MI->getParent())
+        return true;
       // Keep looking unless it is perfect.
-      if (BestGrowth == 0)
+      if (!IgnoreGrowth && BestGrowth == 0)
         return true;
     }
     if (IP == B)
@@ -1479,7 +1483,8 @@
 /// is out-of-range.  If so, pick up the constant pool value and move it some
 /// place in-range.  Return true if we changed any addresses (thus must run
 /// another pass of branch lengthening), false otherwise.
-bool ARMConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
+bool ARMConstantIslands::handleConstantPoolUser(unsigned CPUserIndex,
+                                                bool IgnoreGrowth) {
   CPUser &U = CPUsers[CPUserIndex];
   MachineInstr *UserMI = U.MI;
   MachineInstr *CPEMI  = U.CPEMI;
@@ -1502,7 +1507,7 @@
   MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
   MachineBasicBlock *NewMBB;
   water_iterator IP;
-  if (findAvailableWater(U, UserOffset, IP)) {
+  if (findAvailableWater(U, UserOffset, IP, IgnoreGrowth)) {
     DEBUG(dbgs() << "Found water in range\n");
     MachineBasicBlock *WaterBB = *IP;
 


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