[llvm] 7b57ef6 - llvm-reduce: Simplify virtual register cloning

[Matt Arsenault via llvm-commits]

Author: Matt Arsenault
Date: 2022-04-26T13:17:13-04:00
New Revision: 7b57ef670c64e31bbaa19ae9a3acf0d3ed7f5e73

URL: https://github.com/llvm/llvm-project/commit/7b57ef670c64e31bbaa19ae9a3acf0d3ed7f5e73
DIFF: https://github.com/llvm/llvm-project/commit/7b57ef670c64e31bbaa19ae9a3acf0d3ed7f5e73.diff

LOG: llvm-reduce: Simplify virtual register cloning

Just clone all the virtual registers instead of looking for def
operands. This preserves the register values used, simplifying the
rest of the code. This avoids needing to expose the register map to
target code.

Added: 
    

Modified: 
    llvm/tools/llvm-reduce/ReducerWorkItem.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/tools/llvm-reduce/ReducerWorkItem.cpp b/llvm/tools/llvm-reduce/ReducerWorkItem.cpp
index 1e186221bbb51..547c78606ec62 100644
--- a/llvm/tools/llvm-reduce/ReducerWorkItem.cpp
+++ b/llvm/tools/llvm-reduce/ReducerWorkItem.cpp
@@ -123,7 +123,6 @@ static std::unique_ptr<MachineFunction> cloneMF(MachineFunction *SrcMF) {
       SrcMF->getFunction(), SrcMF->getTarget(), SrcMF->getSubtarget(),
       SrcMF->getFunctionNumber(), SrcMF->getMMI());
   DenseMap<MachineBasicBlock *, MachineBasicBlock *> Src2DstMBB;
-  DenseMap<Register, Register> Src2DstReg;
 
   auto *SrcMRI = &SrcMF->getRegInfo();
   auto *DstMRI = &DstMF->getRegInfo();
@@ -176,50 +175,23 @@ static std::unique_ptr<MachineFunction> cloneMF(MachineFunction *SrcMF) {
 
   // FIXME: Need to clone MachineFunctionInfo, which may also depend on frame
   // index and block mapping.
-
-  // Create vregs.
-  for (auto &SrcMBB : *SrcMF) {
-    for (auto &SrcMI : SrcMBB) {
-      for (unsigned I = 0, E = SrcMI.getNumOperands(); I < E; ++I) {
-        auto &DMO = SrcMI.getOperand(I);
-        if (DMO.isRegMask()) {
-          DstMRI->addPhysRegsUsedFromRegMask(DMO.getRegMask());
-          continue;
-        }
-
-        if (!DMO.isReg())
-          continue;
-        Register SrcReg = DMO.getReg();
-        if (Register::isPhysicalRegister(SrcReg))
-          continue;
-
-        if (Src2DstReg.find(SrcReg) != Src2DstReg.end())
-          continue;
-
-        Register DstReg = DstMRI->createIncompleteVirtualRegister(
-            SrcMRI->getVRegName(SrcReg));
-        DstMRI->setRegClassOrRegBank(DstReg,
-                                     SrcMRI->getRegClassOrRegBank(SrcReg));
-
-        LLT RegTy = SrcMRI->getType(SrcReg);
-        if (RegTy.isValid())
-          DstMRI->setType(DstReg, RegTy);
-        Src2DstReg[SrcReg] = DstReg;
-      }
-    }
-  }
-
-  // Copy register allocation hints.
-  for (std::pair<Register, Register> RegMapEntry : Src2DstReg) {
-    const auto &Hints = SrcMRI->getRegAllocationHints(RegMapEntry.first);
-    for (Register PrefReg : Hints.second) {
-      if (PrefReg.isVirtual()) {
-        auto PrefRegEntry = Src2DstReg.find(PrefReg);
-        assert(PrefRegEntry !=Src2DstReg.end());
-        DstMRI->addRegAllocationHint(RegMapEntry.second, PrefRegEntry->second);
-      } else
-        DstMRI->addRegAllocationHint(RegMapEntry.second, PrefReg);
-    }
+  // Clone virtual registers
+  for (unsigned I = 0, E = SrcMRI->getNumVirtRegs(); I != E; ++I) {
+    Register Reg = Register::index2VirtReg(I);
+    Register NewReg = DstMRI->createIncompleteVirtualRegister(
+      SrcMRI->getVRegName(Reg));
+    assert(NewReg == Reg && "expected to preserve virtreg number");
+
+    DstMRI->setRegClassOrRegBank(NewReg, SrcMRI->getRegClassOrRegBank(Reg));
+
+    LLT RegTy = SrcMRI->getType(Reg);
+    if (RegTy.isValid())
+      DstMRI->setType(NewReg, RegTy);
+
+    // Copy register allocation hints.
+    const auto &Hints = SrcMRI->getRegAllocationHints(Reg);
+    for (Register PrefReg : Hints.second)
+      DstMRI->addRegAllocationHint(NewReg, PrefReg);
   }
 
   const TargetSubtargetInfo &STI = DstMF->getSubtarget();
@@ -258,14 +230,12 @@ static std::unique_ptr<MachineFunction> cloneMF(MachineFunction *SrcMF) {
       for (auto &SrcMO : SrcMI.operands()) {
         MachineOperand DstMO(SrcMO);
         DstMO.clearParent();
-        // Update vreg.
-        if (DstMO.isReg() && Src2DstReg.count(DstMO.getReg())) {
-          DstMO.setReg(Src2DstReg[DstMO.getReg()]);
-        }
+
         // Update MBB.
-        if (DstMO.isMBB()) {
+        if (DstMO.isMBB())
           DstMO.setMBB(Src2DstMBB[DstMO.getMBB()]);
-        }
+        else if (DstMO.isRegMask())
+          DstMRI->addPhysRegsUsedFromRegMask(DstMO.getRegMask());
 
         DstMI->addOperand(DstMO);
       }