The stack slots which share the same stack slot after coloring can, but do not have to, use the same register. In fact, they each may have different register class requirements.

llvm-svn: 70815

1 files changed, 37 insertions, 44 deletions

diff --git a/llvm/lib/CodeGen/StackSlotColoring.cpp b/llvm/lib/CodeGen/StackSlotColoring.cpp
index 6406b1cc251..dd36bdd6041 100644
--- a/llvm/lib/CodeGen/StackSlotColoring.cpp
+++ b/llvm/lib/CodeGen/StackSlotColoring.cpp
@@ -232,61 +232,54 @@ StackSlotColoring::ColorSlotsWithFreeRegs(SmallVector<int, 16> &SlotMapping,
     int SS = li->getStackSlotIndex();
     if (!UsedColors[SS])
       continue;
-    // Get the largest common sub- register class of all the stack slots that
-    // are colored to this stack slot.
-    const TargetRegisterClass *RC = 0;
-    for (unsigned j = 0, ee = RevMap[SS].size(); j != ee; ++j) {
-      int RSS = RevMap[SS][j];
-      const TargetRegisterClass *RRC = LS->getIntervalRegClass(RSS);
-      if (!RC)
-        RC = RRC;
-      else
-        RC = getCommonSubClass(RC, RRC);
-    }
 
-    // If it's not colored to another stack slot, try coloring it
-    // to a "free" register.
-    if (!RC)
-      continue;
-    unsigned Reg = VRM->getFirstUnusedRegister(RC);
-    if (!Reg)
-      continue;
-    bool IsSafe = true;
+    // These slots allow to share the same registers.
+    bool AllColored = true;
+    SmallVector<unsigned, 4> ColoredRegs;
     for (unsigned j = 0, ee = RevMap[SS].size(); j != ee; ++j) {
       int RSS = RevMap[SS][j];
+      const TargetRegisterClass *RC = LS->getIntervalRegClass(RSS);
+      // If it's not colored to another stack slot, try coloring it
+      // to a "free" register.
+      if (!RC) {
+        AllColored = false;
+        continue;
+      }
+      unsigned Reg = VRM->getFirstUnusedRegister(RC);
+      if (!Reg) {
+        AllColored = false;
+        continue;
+      }
       if (!AllMemRefsCanBeUnfolded(RSS)) {
-        IsSafe = false;
-        break;
+        AllColored = false;
+        continue;
+      } else {
+        DOUT << "Assigning fi#" << RSS << " to " << TRI->getName(Reg) << '\n';
+        ColoredRegs.push_back(Reg);
+        SlotMapping[RSS] = Reg;
+        SlotIsReg.set(RSS);
+        Changed = true;
       }
     }
-    if (!IsSafe)
-      // Try color the next spill slot.
-      continue;
 
-    DOUT << "Assigning fi#" << SS << " to " << TRI->getName(Reg)
-         << ", which in turn means...\n";
     // Register and its sub-registers are no longer free.
-    VRM->setRegisterUsed(Reg);
-    // If reg is a callee-saved register, it will have to be spilled in
-    // the prologue.
-    MRI->setPhysRegUsed(Reg);
-    for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) {
-      VRM->setRegisterUsed(*AS);
-      MRI->setPhysRegUsed(*AS);
+    while (!ColoredRegs.empty()) {
+      unsigned Reg = ColoredRegs.back();
+      ColoredRegs.pop_back();
+      VRM->setRegisterUsed(Reg);
+      // If reg is a callee-saved register, it will have to be spilled in
+      // the prologue.
+      MRI->setPhysRegUsed(Reg);
+      for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) {
+        VRM->setRegisterUsed(*AS);
+        MRI->setPhysRegUsed(*AS);
+      }
     }
     // This spill slot is dead after the rewrites
-    MFI->RemoveStackObject(SS);
-
-    // Remember all these FI references will have to be unfolded.
-    for (unsigned j = 0, ee = RevMap[SS].size(); j != ee; ++j) {
-      int RSS = RevMap[SS][j];
-      DOUT << "  Assigning fi#" << RSS << " to " << TRI->getName(Reg) << '\n';
-      SlotMapping[RSS] = Reg;
-      SlotIsReg.set(RSS);
+    if (AllColored) {
+      MFI->RemoveStackObject(SS);
+      ++NumEliminated;
     }
-
-    ++NumEliminated;
-    Changed = true;
   }
   DOUT << '\n';