Revert "[LoongArch] Add isSafeToMove hook to prevent unsafe instruction motion"

[heiher]

Reverts #163725

[llvmbot]

@llvm/pr-subscribers-backend-loongarch

Author: hev (heiher)

Changes

Reverts llvm/llvm-project#163725

---

Full diff: https://github.com/llvm/llvm-project/pull/167463.diff

4 Files Affected:

• (modified) llvm/include/llvm/CodeGen/TargetInstrInfo.h (-11)
• (modified) llvm/lib/CodeGen/BranchFolding.cpp (-5)
• (modified) llvm/lib/Target/LoongArch/LoongArchInstrInfo.cpp (+18-27)
• (modified) llvm/lib/Target/LoongArch/LoongArchInstrInfo.h (-3)

diff --git a/llvm/include/llvm/CodeGen/TargetInstrInfo.h b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
index 18142c2c0adf3..43f28ed79f9dd 100644
--- a/llvm/include/llvm/CodeGen/TargetInstrInfo.h
+++ b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
@@ -1765,17 +1765,6 @@ class LLVM_ABI TargetInstrInfo : public MCInstrInfo {
     return true;
   }
 
-  /// Return true if it's safe to move a machine instruction.
-  /// This allows the backend to prevent certain special instruction
-  /// sequences from being broken by instruction motion in optimization
-  /// passes.
-  /// By default, this returns true for every instruction.
-  virtual bool isSafeToMove(const MachineInstr &MI,
-                            const MachineBasicBlock *MBB,
-                            const MachineFunction &MF) const {
-    return true;
-  }
-
   /// Test if the given instruction should be considered a scheduling boundary.
   /// This primarily includes labels and terminators.
   virtual bool isSchedulingBoundary(const MachineInstr &MI,
diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index af1625a209569..7292bc2be0df2 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -1979,7 +1979,6 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
   MachineBasicBlock::iterator FIB = FBB->begin();
   MachineBasicBlock::iterator TIE = TBB->end();
   MachineBasicBlock::iterator FIE = FBB->end();
-  MachineFunction &MF = *MBB->getParent();
   while (TIB != TIE && FIB != FIE) {
     // Skip dbg_value instructions. These do not count.
     TIB = skipDebugInstructionsForward(TIB, TIE, false);
@@ -1994,10 +1993,6 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
       // Hard to reason about register liveness with predicated instruction.
       break;
 
-    if (!TII->isSafeToMove(*TIB, MBB, MF))
-      // Don't hoist the instruction if it isn't safe to move.
-      break;
-
     bool IsSafe = true;
     for (MachineOperand &MO : TIB->operands()) {
       // Don't attempt to hoist instructions with register masks.
diff --git a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.cpp b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.cpp
index 9fc862af7ea24..9a33dccd002c7 100644
--- a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.cpp
+++ b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.cpp
@@ -378,9 +378,12 @@ bool LoongArchInstrInfo::isBranchOffsetInRange(unsigned BranchOp,
   }
 }
 
-bool LoongArchInstrInfo::isSafeToMove(const MachineInstr &MI,
-                                      const MachineBasicBlock *MBB,
-                                      const MachineFunction &MF) const {
+bool LoongArchInstrInfo::isSchedulingBoundary(const MachineInstr &MI,
+                                              const MachineBasicBlock *MBB,
+                                              const MachineFunction &MF) const {
+  if (TargetInstrInfo::isSchedulingBoundary(MI, MBB, MF))
+    return true;
+
   auto MII = MI.getIterator();
   auto MIE = MBB->end();
 
@@ -426,25 +429,25 @@ bool LoongArchInstrInfo::isSafeToMove(const MachineInstr &MI,
     auto MO2 = Lu32I->getOperand(2).getTargetFlags();
     if (MO0 == LoongArchII::MO_PCREL_HI && MO1 == LoongArchII::MO_PCREL_LO &&
         MO2 == LoongArchII::MO_PCREL64_LO)
-      return false;
+      return true;
     if ((MO0 == LoongArchII::MO_GOT_PC_HI || MO0 == LoongArchII::MO_LD_PC_HI ||
          MO0 == LoongArchII::MO_GD_PC_HI) &&
         MO1 == LoongArchII::MO_GOT_PC_LO && MO2 == LoongArchII::MO_GOT_PC64_LO)
-      return false;
+      return true;
     if (MO0 == LoongArchII::MO_IE_PC_HI && MO1 == LoongArchII::MO_IE_PC_LO &&
         MO2 == LoongArchII::MO_IE_PC64_LO)
-      return false;
+      return true;
     if (MO0 == LoongArchII::MO_DESC_PC_HI &&
         MO1 == LoongArchII::MO_DESC_PC_LO &&
         MO2 == LoongArchII::MO_DESC64_PC_LO)
-      return false;
+      return true;
     break;
   }
   case LoongArch::LU52I_D: {
     auto MO = MI.getOperand(2).getTargetFlags();
     if (MO == LoongArchII::MO_PCREL64_HI || MO == LoongArchII::MO_GOT_PC64_HI ||
         MO == LoongArchII::MO_IE_PC64_HI || MO == LoongArchII::MO_DESC64_PC_HI)
-      return false;
+      return true;
     break;
   }
   default:
@@ -484,7 +487,7 @@ bool LoongArchInstrInfo::isSafeToMove(const MachineInstr &MI,
         auto MO1 = LoongArchII::getDirectFlags(SecondOp->getOperand(2));
         auto MO2 = LoongArchII::getDirectFlags(Ld->getOperand(2));
         if (MO1 == LoongArchII::MO_DESC_PC_LO && MO2 == LoongArchII::MO_DESC_LD)
-          return false;
+          return true;
         break;
       }
       if (SecondOp == MIE ||
@@ -493,34 +496,34 @@ bool LoongArchInstrInfo::isSafeToMove(const MachineInstr &MI,
       auto MO1 = LoongArchII::getDirectFlags(SecondOp->getOperand(2));
       if (MO0 == LoongArchII::MO_PCREL_HI && SecondOp->getOpcode() == AddiOp &&
           MO1 == LoongArchII::MO_PCREL_LO)
-        return false;
+        return true;
       if (MO0 == LoongArchII::MO_GOT_PC_HI && SecondOp->getOpcode() == LdOp &&
           MO1 == LoongArchII::MO_GOT_PC_LO)
-        return false;
+        return true;
       if ((MO0 == LoongArchII::MO_LD_PC_HI ||
            MO0 == LoongArchII::MO_GD_PC_HI) &&
           SecondOp->getOpcode() == AddiOp && MO1 == LoongArchII::MO_GOT_PC_LO)
-        return false;
+        return true;
       break;
     }
     case LoongArch::ADDI_W:
     case LoongArch::ADDI_D: {
       auto MO = LoongArchII::getDirectFlags(MI.getOperand(2));
       if (MO == LoongArchII::MO_PCREL_LO || MO == LoongArchII::MO_GOT_PC_LO)
-        return false;
+        return true;
       break;
     }
     case LoongArch::LD_W:
     case LoongArch::LD_D: {
       auto MO = LoongArchII::getDirectFlags(MI.getOperand(2));
       if (MO == LoongArchII::MO_GOT_PC_LO)
-        return false;
+        return true;
       break;
     }
     case LoongArch::PseudoDESC_CALL: {
       auto MO = LoongArchII::getDirectFlags(MI.getOperand(2));
       if (MO == LoongArchII::MO_DESC_CALL)
-        return false;
+        return true;
       break;
     }
     default:
@@ -528,18 +531,6 @@ bool LoongArchInstrInfo::isSafeToMove(const MachineInstr &MI,
     }
   }
 
-  return true;
-}
-
-bool LoongArchInstrInfo::isSchedulingBoundary(const MachineInstr &MI,
-                                              const MachineBasicBlock *MBB,
-                                              const MachineFunction &MF) const {
-  if (TargetInstrInfo::isSchedulingBoundary(MI, MBB, MF))
-    return true;
-
-  if (!isSafeToMove(MI, MBB, MF))
-    return true;
-
   return false;
 }
 
diff --git a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.h b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.h
index 9f7a0a2239a87..796ef9f3a5715 100644
--- a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.h
+++ b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.h
@@ -66,9 +66,6 @@ class LoongArchInstrInfo : public LoongArchGenInstrInfo {
   bool isBranchOffsetInRange(unsigned BranchOpc,
                              int64_t BrOffset) const override;
 
-  bool isSafeToMove(const MachineInstr &MI, const MachineBasicBlock *MBB,
-                    const MachineFunction &MF) const override;
-
   bool isSchedulingBoundary(const MachineInstr &MI,
                             const MachineBasicBlock *MBB,
                             const MachineFunction &MF) const override;