ExecutionDepsFix: Correctly handle wide registers.

The ExecutionDepsFix previously mapped each register to 1 or zero
registers of the register class it was called with and therefore
simulating liveness for.  This was problematic for cases involving wider
registers like Q0 on ARM where ExecutionDepsFix gets invoked for the Dxx
registers. In these cases the wide register would get mapped to the last
matching D register, while it should have been all matching D registers.
This commit changes the AliasMap to use a SmallVector to map registers
to potentially multiple destination regclass registers. This is required
to avoid regressions with subregister liveness tracking enabled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224447 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/ExecutionDepsFix.cpp b/lib/CodeGen/ExecutionDepsFix.cpp
index 9d3ba5e0a55e83a3231c6b3d73a716e75951ae78..b3a22c83a80867f20ffe3f9b9f72ad82c86ca3e5 100644 (file)
--- a/lib/CodeGen/ExecutionDepsFix.cpp
+++ b/lib/CodeGen/ExecutionDepsFix.cpp
@@ -22,6 +22,7 @@
 
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/iterator_range.h"
 #include "llvm/CodeGen/LivePhysRegs.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
@@ -136,7 +137,7 @@ class ExeDepsFix : public MachineFunctionPass {
   MachineFunction *MF;
   const TargetInstrInfo *TII;
   const TargetRegisterInfo *TRI;
-  std::vector<int> AliasMap;
+  std::vector<SmallVector<int, 1>> AliasMap;
   const unsigned NumRegs;
   LiveReg *LiveRegs;
   typedef DenseMap<MachineBasicBlock*, LiveReg*> LiveOutMap;
@@ -172,8 +173,8 @@ public:
   }
 
 private:
-  // Register mapping.
-  int regIndex(unsigned Reg);
+  iterator_range<SmallVectorImpl<int>::const_iterator>
+  regIndizes(unsigned Reg) const;
 
   // DomainValue allocation.
   DomainValue *alloc(int domain = -1);
@@ -204,11 +205,13 @@ private:
 
 char ExeDepsFix::ID = 0;
 
-/// Translate TRI register number to an index into our smaller tables of
-/// interesting registers. Return -1 for boring registers.
-int ExeDepsFix::regIndex(unsigned Reg) {
+/// Translate TRI register number to a list of indizes into our stmaller tables
+/// of interesting registers.
+iterator_range<SmallVectorImpl<int>::const_iterator>
+ExeDepsFix::regIndizes(unsigned Reg) const {
   assert(Reg < AliasMap.size() && "Invalid register");
-  return AliasMap[Reg];
+  const auto &Entry = AliasMap[Reg];
+  return make_range(Entry.begin(), Entry.end());
 }
 
 DomainValue *ExeDepsFix::alloc(int domain) {
@@ -375,13 +378,12 @@ void ExeDepsFix::enterBasicBlock(MachineBasicBlock *MBB) {
   if (MBB->pred_empty()) {
     for (MachineBasicBlock::livein_iterator i = MBB->livein_begin(),
          e = MBB->livein_end(); i != e; ++i) {
-      int rx = regIndex(*i);
-      if (rx < 0)
-        continue;
-      // Treat function live-ins as if they were defined just before the first
-      // instruction.  Usually, function arguments are set up immediately
-      // before the call.
-      LiveRegs[rx].Def = -1;
+      for (int rx : regIndizes(*i)) {
+        // Treat function live-ins as if they were defined just before the first
+        // instruction.  Usually, function arguments are set up immediately
+        // before the call.
+        LiveRegs[rx].Def = -1;
+      }
     }
     DEBUG(dbgs() << "BB#" << MBB->getNumber() << ": entry\n");
     return;
@@ -472,26 +474,26 @@ void ExeDepsFix::visitInstr(MachineInstr *MI) {
 /// or undef use.
 bool ExeDepsFix::shouldBreakDependence(MachineInstr *MI, unsigned OpIdx,
                                        unsigned Pref) {
-  int rx = regIndex(MI->getOperand(OpIdx).getReg());
-  if (rx < 0)
-    return false;
+  unsigned reg = MI->getOperand(OpIdx).getReg();
+  for (int rx : regIndizes(reg)) {
+    unsigned Clearance = CurInstr - LiveRegs[rx].Def;
+    DEBUG(dbgs() << "Clearance: " << Clearance << ", want " << Pref);
 
-  unsigned Clearance = CurInstr - LiveRegs[rx].Def;
-  DEBUG(dbgs() << "Clearance: " << Clearance << ", want " << Pref);
-
-  if (Pref > Clearance) {
-    DEBUG(dbgs() << ": Break dependency.\n");
-    return true;
-  }
-  // The current clearance seems OK, but we may be ignoring a def from a
-  // back-edge.
-  if (!SeenUnknownBackEdge || Pref <= unsigned(CurInstr)) {
-    DEBUG(dbgs() << ": OK .\n");
+    if (Pref > Clearance) {
+      DEBUG(dbgs() << ": Break dependency.\n");
+      continue;
+    }
+    // The current clearance seems OK, but we may be ignoring a def from a
+    // back-edge.
+    if (!SeenUnknownBackEdge || Pref <= unsigned(CurInstr)) {
+      DEBUG(dbgs() << ": OK .\n");
+      return false;
+    }
+    // A def from an unprocessed back-edge may make us break this dependency.
+    DEBUG(dbgs() << ": Wait for back-edge to resolve.\n");
     return false;
   }
-  // A def from an unprocessed back-edge may make us break this dependency.
-  DEBUG(dbgs() << ": Wait for back-edge to resolve.\n");
-  return false;
+  return true;
 }
 
 // Update def-ages for registers defined by MI.
@@ -519,26 +521,24 @@ void ExeDepsFix::processDefs(MachineInstr *MI, bool Kill) {
       break;
     if (MO.isUse())
       continue;
-    int rx = regIndex(MO.getReg());
-    if (rx < 0)
-      continue;
-
-    // This instruction explicitly defines rx.
-    DEBUG(dbgs() << TRI->getName(RC->getRegister(rx)) << ":\t" << CurInstr
-                 << '\t' << *MI);
-
-    // Check clearance before partial register updates.
-    // Call breakDependence before setting LiveRegs[rx].Def.
-    unsigned Pref = TII->getPartialRegUpdateClearance(MI, i, TRI);
-    if (Pref && shouldBreakDependence(MI, i, Pref))
-      TII->breakPartialRegDependency(MI, i, TRI);
-
-    // How many instructions since rx was last written?
-    LiveRegs[rx].Def = CurInstr;
-
-    // Kill off domains redefined by generic instructions.
-    if (Kill)
-      kill(rx);
+    for (int rx : regIndizes(MO.getReg())) {
+      // This instruction explicitly defines rx.
+      DEBUG(dbgs() << TRI->getName(RC->getRegister(rx)) << ":\t" << CurInstr
+                   << '\t' << *MI);
+
+      // Check clearance before partial register updates.
+      // Call breakDependence before setting LiveRegs[rx].Def.
+      unsigned Pref = TII->getPartialRegUpdateClearance(MI, i, TRI);
+      if (Pref && shouldBreakDependence(MI, i, Pref))
+        TII->breakPartialRegDependency(MI, i, TRI);
+
+      // How many instructions since rx was last written?
+      LiveRegs[rx].Def = CurInstr;
+
+      // Kill off domains redefined by generic instructions.
+      if (Kill)
+        kill(rx);
+    }
   }
   ++CurInstr;
 }
@@ -587,19 +587,19 @@ void ExeDepsFix::visitHardInstr(MachineInstr *mi, unsigned domain) {
                 e = mi->getDesc().getNumOperands(); i != e; ++i) {
     MachineOperand &mo = mi->getOperand(i);
     if (!mo.isReg()) continue;
-    int rx = regIndex(mo.getReg());
-    if (rx < 0) continue;
-    force(rx, domain);
+    for (int rx : regIndizes(mo.getReg())) {
+      force(rx, domain);
+    }
   }
 
   // Kill all defs and force them.
   for (unsigned i = 0, e = mi->getDesc().getNumDefs(); i != e; ++i) {
     MachineOperand &mo = mi->getOperand(i);
     if (!mo.isReg()) continue;
-    int rx = regIndex(mo.getReg());
-    if (rx < 0) continue;
-    kill(rx);
-    force(rx, domain);
+    for (int rx : regIndizes(mo.getReg())) {
+      kill(rx);
+      force(rx, domain);
+    }
   }
 }
 
@@ -616,9 +616,10 @@ void ExeDepsFix::visitSoftInstr(MachineInstr *mi, unsigned mask) {
                   e = mi->getDesc().getNumOperands(); i != e; ++i) {
       MachineOperand &mo = mi->getOperand(i);
       if (!mo.isReg()) continue;
-      int rx = regIndex(mo.getReg());
-      if (rx < 0) continue;
-      if (DomainValue *dv = LiveRegs[rx].Value) {
+      for (int rx : regIndizes(mo.getReg())) {
+        DomainValue *dv = LiveRegs[rx].Value;
+        if (dv == nullptr)
+          continue;
         // Bitmask of domains that dv and available have in common.
         unsigned common = dv->getCommonDomains(available);
         // Is it possible to use this collapsed register for free?
@@ -711,11 +712,11 @@ void ExeDepsFix::visitSoftInstr(MachineInstr *mi, unsigned mask) {
                                   ii != ee; ++ii) {
     MachineOperand &mo = *ii;
     if (!mo.isReg()) continue;
-    int rx = regIndex(mo.getReg());
-    if (rx < 0) continue;
-    if (!LiveRegs[rx].Value || (mo.isDef() && LiveRegs[rx].Value != dv)) {
-      kill(rx);
-      setLiveReg(rx, dv);
+    for (int rx : regIndizes(mo.getReg())) {
+      if (!LiveRegs[rx].Value || (mo.isDef() && LiveRegs[rx].Value != dv)) {
+        kill(rx);
+        setLiveReg(rx, dv);
+      }
     }
   }
 }
@@ -743,13 +744,13 @@ bool ExeDepsFix::runOnMachineFunction(MachineFunction &mf) {
 
   // Initialize the AliasMap on the first use.
   if (AliasMap.empty()) {
-    // Given a PhysReg, AliasMap[PhysReg] is either the relevant index into RC,
-    // or -1.
-    AliasMap.resize(TRI->getNumRegs(), -1);
+    // Given a PhysReg, AliasMap[PhysReg] returns a list of indices into RC and
+    // therefore the LiveRegs array.
+    AliasMap.resize(TRI->getNumRegs());
     for (unsigned i = 0, e = RC->getNumRegs(); i != e; ++i)
       for (MCRegAliasIterator AI(RC->getRegister(i), TRI, true);
            AI.isValid(); ++AI)
-        AliasMap[*AI] = i;
+        AliasMap[*AI].push_back(i);
   }
 
   MachineBasicBlock *Entry = MF->begin();