Revert "Refactor recomputeLiveIns to operate on whole CFG (#79498)"

This reverts commit 59bf605.

Introduces a major compile-time regression.

Author: nikic

llvm/include/llvm/CodeGen/LivePhysRegs.h

@@ -31,7 +31,6 @@
 
 #include "llvm/ADT/SparseSet.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
-#include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/MC/MCRegister.h"
 #include "llvm/MC/MCRegisterInfo.h"
@@ -194,31 +193,11 @@ void addLiveIns(MachineBasicBlock &MBB, const LivePhysRegs &LiveRegs);
 void computeAndAddLiveIns(LivePhysRegs &LiveRegs,
                           MachineBasicBlock &MBB);
 
-/// Function to update the live-in's for a basic block and return whether any
-/// changes were made.
-static inline bool updateBlockLiveInfo(MachineBasicBlock &MBB) {
+/// Convenience function for recomputing live-in's for \p MBB.
+static inline void recomputeLiveIns(MachineBasicBlock &MBB) {
   LivePhysRegs LPR;
-  auto oldLiveIns = MBB.getLiveIns();
-
   MBB.clearLiveIns();
   computeAndAddLiveIns(LPR, MBB);
-  MBB.sortUniqueLiveIns();
-
-  auto newLiveIns = MBB.getLiveIns();
-  return oldLiveIns != newLiveIns;
-}
-
-/// Convenience function for recomputing live-in's for the entire CFG until
-/// convergence is reached.
-static inline void recomputeLiveIns(MachineFunction &MF) {
-  bool anyChanged;
-  do {
-    anyChanged = false;
-    for (auto MFI = MF.rbegin(), MFE = MF.rend(); MFI != MFE; ++MFI) {
-      MachineBasicBlock &MBB = *MFI;
-      anyChanged |= updateBlockLiveInfo(MBB);
-    }
-  } while (anyChanged);
 }
 
 } // end namespace llvm

llvm/include/llvm/CodeGen/MachineBasicBlock.h

@@ -111,10 +111,6 @@ class MachineBasicBlock
 
     RegisterMaskPair(MCPhysReg PhysReg, LaneBitmask LaneMask)
         : PhysReg(PhysReg), LaneMask(LaneMask) {}
-
-    bool operator==(const RegisterMaskPair &other) const {
-      return PhysReg == other.PhysReg && LaneMask == other.LaneMask;
-    }
   };
 
 private:
@@ -477,8 +473,6 @@ class MachineBasicBlock
   /// Remove entry from the livein set and return iterator to the next.
   livein_iterator removeLiveIn(livein_iterator I);
 
-  std::vector<RegisterMaskPair> getLiveIns() const { return LiveIns; }
-
   class liveout_iterator {
   public:
     using iterator_category = std::input_iterator_tag;

llvm/lib/CodeGen/BranchFolding.cpp

@@ -2048,7 +2048,8 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
   FBB->erase(FBB->begin(), FIB);
 
   if (UpdateLiveIns) {
-    recomputeLiveIns(*MBB->getParent());
+    recomputeLiveIns(*TBB);
+    recomputeLiveIns(*FBB);
   }
 
   ++NumHoist;

llvm/lib/Target/AArch64/AArch64FrameLowering.cpp

@@ -4339,7 +4339,8 @@ AArch64FrameLowering::inlineStackProbeLoopExactMultiple(
   ExitMBB->transferSuccessorsAndUpdatePHIs(&MBB);
   MBB.addSuccessor(LoopMBB);
   // Update liveins.
-  recomputeLiveIns(MF);
+  recomputeLiveIns(*LoopMBB);
+  recomputeLiveIns(*ExitMBB);
 
   return ExitMBB->begin();
 }

llvm/lib/Target/AArch64/AArch64InstrInfo.cpp

@@ -9597,7 +9597,9 @@ AArch64InstrInfo::probedStackAlloc(MachineBasicBlock::iterator MBBI,
 
   // Update liveins.
   if (MF.getRegInfo().reservedRegsFrozen()) {
-    recomputeLiveIns(MF);
+    recomputeLiveIns(*LoopTestMBB);
+    recomputeLiveIns(*LoopBodyMBB);
+    recomputeLiveIns(*ExitMBB);
   }
 
   return ExitMBB->begin();

llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp

@@ -1806,7 +1806,12 @@ void ARMLowOverheadLoops::Expand(LowOverheadLoop &LoLoop) {
   PostOrderLoopTraversal DFS(LoLoop.ML, *MLI);
   DFS.ProcessLoop();
   const SmallVectorImpl<MachineBasicBlock*> &PostOrder = DFS.getOrder();
-  recomputeLiveIns(*LoLoop.MF);
+  for (auto *MBB : PostOrder) {
+    recomputeLiveIns(*MBB);
+    // FIXME: For some reason, the live-in print order is non-deterministic for
+    // our tests and I can't out why... So just sort them.
+    MBB->sortUniqueLiveIns();
+  }
 
   for (auto *MBB : reverse(PostOrder))
     recomputeLivenessFlags(*MBB);

llvm/lib/Target/PowerPC/PPCExpandAtomicPseudoInsts.cpp

@@ -208,7 +208,8 @@ bool PPCExpandAtomicPseudo::expandAtomicRMW128(
       .addMBB(LoopMBB);
   CurrentMBB->addSuccessor(LoopMBB);
   CurrentMBB->addSuccessor(ExitMBB);
-  recomputeLiveIns(*MF);
+  recomputeLiveIns(*LoopMBB);
+  recomputeLiveIns(*ExitMBB);
   NMBBI = MBB.end();
   MI.eraseFromParent();
   return true;
@@ -285,7 +286,9 @@ bool PPCExpandAtomicPseudo::expandAtomicCmpSwap128(
   CurrentMBB->addSuccessor(LoopCmpMBB);
   CurrentMBB->addSuccessor(ExitMBB);
 
-  recomputeLiveIns(*MF);
+  recomputeLiveIns(*LoopCmpMBB);
+  recomputeLiveIns(*CmpSuccMBB);
+  recomputeLiveIns(*ExitMBB);
   NMBBI = MBB.end();
   MI.eraseFromParent();
   return true;

llvm/lib/Target/PowerPC/PPCFrameLowering.cpp

@@ -1441,7 +1441,8 @@ void PPCFrameLowering::inlineStackProbe(MachineFunction &MF,
       ProbeLoopBodyMBB->addSuccessor(ProbeLoopBodyMBB);
     }
     // Update liveins.
-    recomputeLiveIns(MF);
+    recomputeLiveIns(*ProbeLoopBodyMBB);
+    recomputeLiveIns(*ProbeExitMBB);
     return ProbeExitMBB;
   };
   // For case HasBP && MaxAlign > 1, we have to realign the SP by performing
@@ -1533,7 +1534,8 @@ void PPCFrameLowering::inlineStackProbe(MachineFunction &MF,
         buildDefCFAReg(*ExitMBB, ExitMBB->begin(), SPReg);
       }
       // Update liveins.
-      recomputeLiveIns(MF);
+      recomputeLiveIns(*LoopMBB);
+      recomputeLiveIns(*ExitMBB);
     }
   }
   ++NumPrologProbed;

llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp

@@ -840,7 +840,8 @@ void SystemZELFFrameLowering::inlineStackProbe(
   StackAllocMI->eraseFromParent();
   if (DoneMBB != nullptr) {
     // Compute the live-in lists for the new blocks.
-    recomputeLiveIns(MF);
+    recomputeLiveIns(*DoneMBB);
+    recomputeLiveIns(*LoopMBB);
   }
 }
 
@@ -1438,7 +1439,8 @@ void SystemZXPLINKFrameLowering::inlineStackProbe(
   StackAllocMI->eraseFromParent();
 
   // Compute the live-in lists for the new blocks.
-  recomputeLiveIns(MF);
+  recomputeLiveIns(*NextMBB);
+  recomputeLiveIns(*StackExtMBB);
 }
 
 bool SystemZXPLINKFrameLowering::hasFP(const MachineFunction &MF) const {

llvm/lib/Target/X86/X86FrameLowering.cpp

@@ -885,7 +885,8 @@ void X86FrameLowering::emitStackProbeInlineGenericLoop(
   }
 
   // Update Live In information
-  recomputeLiveIns(MF);
+  recomputeLiveIns(*testMBB);
+  recomputeLiveIns(*tailMBB);
 }
 
 void X86FrameLowering::emitStackProbeInlineWindowsCoreCLR64(
@@ -1377,7 +1378,10 @@ void X86FrameLowering::BuildStackAlignAND(MachineBasicBlock &MBB,
         footMBB->addSuccessor(&MBB);
       }
 
-      recomputeLiveIns(MF);
+      recomputeLiveIns(*headMBB);
+      recomputeLiveIns(*bodyMBB);
+      recomputeLiveIns(*footMBB);
+      recomputeLiveIns(MBB);
     }
   } else {
     MachineInstr *MI = BuildMI(MBB, MBBI, DL, TII.get(AndOp), Reg)