[PowerPC] Implement the areMemAccessesTriviallyDisjoint hook

After implemented this hook, we will model the memory dependency in the scheduling dependency graph more precise,
and will have more opportunity to reorder the load/stores, as they didn't have the dependency at some condition

Differential Revision: https://reviews.llvm.org/D63804

llvm-svn: 364886

2 files changed, 72 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
index 22921ace75f..2658a85303f 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -3996,3 +3996,59 @@ unsigned PPCInstrInfo::reduceLoopCount(
   return LoopCountReg;
 }
 
+// Return true if get the base operand, byte offset of an instruction and the
+// memory width. Width is the size of memory that is being loaded/stored.
+bool PPCInstrInfo::getMemOperandWithOffsetWidth(
+  const MachineInstr &LdSt,
+  const MachineOperand *&BaseReg,
+  int64_t &Offset,
+  unsigned &Width,
+  const TargetRegisterInfo *TRI) const {
+  assert(LdSt.mayLoadOrStore() && "Expected a memory operation.");
+
+  // Handle only loads/stores with base register followed by immediate offset.
+  if (LdSt.getNumExplicitOperands() != 3)
+    return false;
+  if (!LdSt.getOperand(1).isImm() || !LdSt.getOperand(2).isReg())
+    return false;
+
+  if (!LdSt.hasOneMemOperand())
+    return false;
+
+  Width = (*LdSt.memoperands_begin())->getSize();
+  Offset = LdSt.getOperand(1).getImm();
+  BaseReg = &LdSt.getOperand(2);
+  return true;
+}
+
+bool PPCInstrInfo::areMemAccessesTriviallyDisjoint(
+    const MachineInstr &MIa, const MachineInstr &MIb,
+    AliasAnalysis * /*AA*/) const {
+  assert(MIa.mayLoadOrStore() && "MIa must be a load or store.");
+  assert(MIb.mayLoadOrStore() && "MIb must be a load or store.");
+
+  if (MIa.hasUnmodeledSideEffects() || MIb.hasUnmodeledSideEffects() ||
+      MIa.hasOrderedMemoryRef() || MIb.hasOrderedMemoryRef())
+    return false;
+
+  // Retrieve the base register, offset from the base register and width. Width
+  // is the size of memory that is being loaded/stored (e.g. 1, 2, 4).  If
+  // base registers are identical, and the offset of a lower memory access +
+  // the width doesn't overlap the offset of a higher memory access,
+  // then the memory accesses are different.
+  const TargetRegisterInfo *TRI = &getRegisterInfo();
+  const MachineOperand *BaseOpA = nullptr, *BaseOpB = nullptr;
+  int64_t OffsetA = 0, OffsetB = 0;
+  unsigned int WidthA = 0, WidthB = 0;
+  if (getMemOperandWithOffsetWidth(MIa, BaseOpA, OffsetA, WidthA, TRI) &&
+      getMemOperandWithOffsetWidth(MIb, BaseOpB, OffsetB, WidthB, TRI)) {
+    if (BaseOpA->isIdenticalTo(*BaseOpB)) {
+      int LowOffset = std::min(OffsetA, OffsetB);
+      int HighOffset = std::max(OffsetA, OffsetB);
+      int LowWidth = (LowOffset == OffsetA) ? WidthA : WidthB;
+      if (LowOffset + LowWidth <= HighOffset)
+        return true;
+    }
+  }
+  return false;
+}
diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.h b/llvm/lib/Target/PowerPC/PPCInstrInfo.h
index 78b04c2c1ca..70fb757e8f1 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.h
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.h
@@ -357,6 +357,22 @@ public:
                             unsigned SrcReg2, int Mask, int Value,
                             const MachineRegisterInfo *MRI) const override;
 
+
+  /// Return true if get the base operand, byte offset of an instruction and
+  /// the memory width. Width is the size of memory that is being
+  /// loaded/stored (e.g. 1, 2, 4, 8).
+  bool getMemOperandWithOffsetWidth(const MachineInstr &LdSt,
+                                    const MachineOperand *&BaseOp,
+                                    int64_t &Offset, unsigned &Width,
+                                    const TargetRegisterInfo *TRI) const;
+
+  /// Return true if two MIs access different memory addresses and false
+  /// otherwise
+  bool
+  areMemAccessesTriviallyDisjoint(const MachineInstr &MIa,
+                                  const MachineInstr &MIb,
+                                  AliasAnalysis *AA = nullptr) const override;
+
   /// GetInstSize - Return the number of bytes of code the specified
   /// instruction may be.  This returns the maximum number of bytes.
   ///