[VENTUS][fix] Fix insert vmv instruction bug when vmv instruction is …

…in JOIN MBB

llvm/lib/Target/RISCV/VentusInsertJoinToVBranch.cpp

@@ -6,43 +6,14 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// In Ventus, if VBranch instructions are generated, we need to insert join
-// instructions in both `else` and `then` branch to tell hardware where these
-// two branches need to join together
+// In ventus, if VBranch instructions are generated, we need to insert setrpc
+// and join instructions to tell hardware where branches need to join
 //
-// we follow the following rules to insert join block and join instruction
-//
-// 1: Legalize all the return block
-//    when there are one more return blocks in machine function, there must be
-//    branches, we need to reduce return blocks number down to 1
-// 1.1: If two return blocks have common nearest parent branch, this two blocks
-//    need to be joined, and we add a hasBeenJoined marker for this parent
-//    branch
-// 1.2: after we complete 1.1 process, there maybe one more return blocks, we
-//    need to further add join block, we recursively build dominator tree for
-//    these return blocks, first we find the nearest common dominator branch for
-//    two return blocks, and then get dominator tree path between dominator
-//    and each return block, we need to check this path in which whether any
-//    other branch blocks exists, ideally, the branch block in path should have
-//    been joined and marked, if not, this path is illegal, these two block can
-//    not be joined
-//
-// 2: Insert join instructions
-// 2.1: we scan through the MachineBasic blocks and check what blocks to insert
-//    join instruction, below MBB represents MachineBasic Block
-// 2.2: The MBB must have one more predecessors and its nearest dominator must
-//     be a VBranch
-// 2.3: Then we analyze the the predecessor of MBB, if the predecessor
-//    has single successor, we add a join instruction to the predecessor end,
-//    other wise, we need to insert a join block between predecessor and MBB
-//
-// WRANING: Do not use -O(1|2|3) optimization option
 //===----------------------------------------------------------------------===//
 
 #include "MCTargetDesc/RISCVMCTargetDesc.h"
 #include "RISCV.h"
 #include "RISCVInstrInfo.h"
-#include "RISCVTargetMachine.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/CodeGen/MachinePostDominators.h"
 #include "llvm/CodeGen/Register.h"
@@ -231,12 +202,13 @@ bool VentusInsertJoinToVBranch::checkJoinMBB(MachineBasicBlock &MBB) const {
     if (MI.getOpcode() != RISCV::VMV_V_X)
       continue;
 
-    // To be removed vmv.v instruction flag
-    bool NeedToBeErased = false;
+    // The number of MBBs where VMV instruction should be inserted into
+    unsigned NumCandidateMBB = 0;
     assert(MI.getOperand(1).isReg() && "unexpected operator");
     auto Defines = MR.def_instructions(MI.getOperand(1).getReg());
     bool IsInSameBlock = false;
-
+    SmallVector<std::pair<MachineBasicBlock *, MachineBasicBlock::iterator>>
+        MBBAndInsertPosPairs;
     for (auto &Def : Defines) {
       unsigned Opcode = Def.getOpcode();
       // FIXME: Find a better way to handle this in tablegen
@@ -257,26 +229,24 @@ bool VentusInsertJoinToVBranch::checkJoinMBB(MachineBasicBlock &MBB) const {
 
       // Check if define instruction is in the predecessors or not
       for (auto *Pre : MBB.predecessors()) {
-        bool NeedToBeInsert = false;
-        MachineBasicBlock::iterator Insert = Pre->begin();
+        MachineBasicBlock::iterator I = Pre->begin();
         for (auto &MI1 : *Pre) {
-          // Get last register definition
-          if (&MI1 == &Def) {
-            Insert = MI1.getIterator();
-            NeedToBeInsert = true;
-            NeedToBeErased = true;
-          }
-        }
-        if (NeedToBeInsert) {
-          Pre->insertAfter(Insert, MF->CloneMachineInstr(&MI));
-          NeedToBeInsert = false; // Init other predecessor insert flag
+          // Last register define in Pre MBB
+          if (&MI1 == &Def)
+            I = MI1.getIterator();
         }
+        NumCandidateMBB++;
+        // Only get last vmv instruction definition, break the loop
+        // FIXME: it worked, but not the best way?
+        MBBAndInsertPosPairs.push_back({Pre, I});
       }
     }
-
-    if (NeedToBeErased) {
+    if (NumCandidateMBB >= 2) {
+      // Means there are more than two blocks need to insert vmv instruction
       IsChanged |= true;
       MBB.addLiveIn(MCRegister(MI.getOperand(0).getReg()));
+      for (auto Pair : MBBAndInsertPosPairs)
+        Pair.first->insertAfter(Pair.second, MF->CloneMachineInstr(&MI));
       MI.eraseFromParent();
     }
   }

llvm/lib/Target/RISCV/VentusRegextInsertion.cpp

@@ -85,7 +85,8 @@ bool VentusRegextInsertion::insertRegext(MachineBasicBlock &MBB,
   for (unsigned i = 0; i < MI.getNumOperands(); ++i) {
     MachineOperand &Op = MI.getOperand(i);
     if (!Op.isReg() ||
-        MI.getDesc().getOperandConstraint(i, MCOI::TIED_TO) != -1)
+        MI.getDesc().getOperandConstraint(i, MCOI::TIED_TO) != -1 ||
+        MI.isDebugInstr() || MI.isPseudo())
       continue;
 
     uint16_t RegEncodingValue = TRI->getEncodingValue(Op.getReg());