[NFC] Refactor looping over recomputeLiveIns into function (#88040)

#79940 put calls to
recomputeLiveIns into
a loop, to repeatedly call the function until the computation converges.
However,
this repeats a lot of code. This changes moves the loop into a function
to simplify
the handling.

Note that this changes the order in which recomputeLiveIns is called.
For example,

```
  bool anyChange = false;
  do {
    anyChange = recomputeLiveIns(*ExitMBB) || recomputeLiveIns(*LoopMBB);
  } while (anyChange);
```

only begins to recompute the live-ins for LoopMBB after the computation
for ExitMBB
has converged. With this change, all basic blocks have a recomputation
of the live-ins
for each loop iteration. This can result in less or more calls,
depending on the
situation.

Author: redstar

llvm/include/llvm/CodeGen/LivePhysRegs.h

@@ -39,6 +39,8 @@
 
 namespace llvm {
 
+template <typename T> class ArrayRef;
+
 class MachineInstr;
 class MachineFunction;
 class MachineOperand;
@@ -207,6 +209,22 @@ static inline bool recomputeLiveIns(MachineBasicBlock &MBB) {
   return oldLiveIns != newLiveIns;
 }
 
+/// Convenience function for recomputing live-in's for a set of MBBs until the
+/// computation converges.
+inline void fullyRecomputeLiveIns(ArrayRef<MachineBasicBlock *> MBBs) {
+  MachineBasicBlock *const *Data = MBBs.data();
+  const size_t Len = MBBs.size();
+  while (true) {
+    bool AnyChange = false;
+    for (size_t I = 0; I < Len; ++I)
+      if (recomputeLiveIns(*Data[I]))
+        AnyChange = true;
+    if (!AnyChange)
+      return;
+  }
+}
+
+
 } // end namespace llvm
 
 #endif // LLVM_CODEGEN_LIVEPHYSREGS_H

llvm/lib/CodeGen/BranchFolding.cpp

@@ -2047,12 +2047,8 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
   MBB->splice(Loc, TBB, TBB->begin(), TIB);
   FBB->erase(FBB->begin(), FIB);
 
-  if (UpdateLiveIns) {
-    bool anyChange = false;
-    do {
-      anyChange = recomputeLiveIns(*TBB) || recomputeLiveIns(*FBB);
-    } while (anyChange);
-  }
+  if (UpdateLiveIns)
+    fullyRecomputeLiveIns({TBB, FBB});
 
   ++NumHoist;
   return true;

llvm/lib/Target/AArch64/AArch64FrameLowering.cpp

@@ -4325,10 +4325,7 @@ AArch64FrameLowering::inlineStackProbeLoopExactMultiple(
   ExitMBB->transferSuccessorsAndUpdatePHIs(&MBB);
   MBB.addSuccessor(LoopMBB);
   // Update liveins.
-  bool anyChange = false;
-  do {
-    anyChange = recomputeLiveIns(*ExitMBB) || recomputeLiveIns(*LoopMBB);
-  } while (anyChange);
+  fullyRecomputeLiveIns({ExitMBB, LoopMBB});
 
   return ExitMBB->begin();
 }

llvm/lib/Target/AArch64/AArch64InstrInfo.cpp

@@ -9556,15 +9556,8 @@ AArch64InstrInfo::probedStackAlloc(MachineBasicBlock::iterator MBBI,
   MBB.addSuccessor(LoopTestMBB);
 
   // Update liveins.
-  if (MF.getRegInfo().reservedRegsFrozen()) {
-    bool anyChange = false;
-    do {
-      anyChange = recomputeLiveIns(*ExitMBB) ||
-                  recomputeLiveIns(*LoopBodyMBB) ||
-                  recomputeLiveIns(*LoopTestMBB);
-    } while (anyChange);
-    ;
-  }
+  if (MF.getRegInfo().reservedRegsFrozen())
+    fullyRecomputeLiveIns({ExitMBB, LoopBodyMBB, LoopTestMBB});
 
   return ExitMBB->begin();
 }

llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp

@@ -1806,13 +1806,7 @@ void ARMLowOverheadLoops::Expand(LowOverheadLoop &LoLoop) {
   PostOrderLoopTraversal DFS(LoLoop.ML, *MLI);
   DFS.ProcessLoop();
   const SmallVectorImpl<MachineBasicBlock*> &PostOrder = DFS.getOrder();
-  bool anyChange = false;
-  do {
-    anyChange = false;
-    for (auto *MBB : PostOrder) {
-      anyChange = recomputeLiveIns(*MBB) || anyChange;
-    }
-  } while (anyChange);
+  fullyRecomputeLiveIns(PostOrder);
 
   for (auto *MBB : reverse(PostOrder))
     recomputeLivenessFlags(*MBB);

llvm/lib/Target/PowerPC/PPCExpandAtomicPseudoInsts.cpp

@@ -208,10 +208,7 @@ bool PPCExpandAtomicPseudo::expandAtomicRMW128(
       .addMBB(LoopMBB);
   CurrentMBB->addSuccessor(LoopMBB);
   CurrentMBB->addSuccessor(ExitMBB);
-  bool anyChange = false;
-  do {
-    anyChange = recomputeLiveIns(*ExitMBB) || recomputeLiveIns(*LoopMBB);
-  } while (anyChange);
+  fullyRecomputeLiveIns({ExitMBB, LoopMBB});
   NMBBI = MBB.end();
   MI.eraseFromParent();
   return true;
@@ -288,11 +285,7 @@ bool PPCExpandAtomicPseudo::expandAtomicCmpSwap128(
   CurrentMBB->addSuccessor(LoopCmpMBB);
   CurrentMBB->addSuccessor(ExitMBB);
 
-  bool anyChange = false;
-  do {
-    anyChange = recomputeLiveIns(*ExitMBB) || recomputeLiveIns(*CmpSuccMBB) ||
-                recomputeLiveIns(*LoopCmpMBB);
-  } while (anyChange);
+  fullyRecomputeLiveIns({ExitMBB, CmpSuccMBB, LoopCmpMBB});
   NMBBI = MBB.end();
   MI.eraseFromParent();
   return true;

llvm/lib/Target/PowerPC/PPCFrameLowering.cpp

@@ -1435,11 +1435,7 @@ void PPCFrameLowering::inlineStackProbe(MachineFunction &MF,
       ProbeLoopBodyMBB->addSuccessor(ProbeLoopBodyMBB);
     }
     // Update liveins.
-    bool anyChange = false;
-    do {
-      anyChange = recomputeLiveIns(*ProbeExitMBB) ||
-                  recomputeLiveIns(*ProbeLoopBodyMBB);
-    } while (anyChange);
+    fullyRecomputeLiveIns({ProbeExitMBB, ProbeLoopBodyMBB});
     return ProbeExitMBB;
   };
   // For case HasBP && MaxAlign > 1, we have to realign the SP by performing
@@ -1531,10 +1527,7 @@ void PPCFrameLowering::inlineStackProbe(MachineFunction &MF,
         buildDefCFAReg(*ExitMBB, ExitMBB->begin(), SPReg);
       }
       // Update liveins.
-      bool anyChange = false;
-      do {
-        anyChange = recomputeLiveIns(*ExitMBB) || recomputeLiveIns(*LoopMBB);
-      } while (anyChange);
+      fullyRecomputeLiveIns({ExitMBB, LoopMBB});
     }
   }
   ++NumPrologProbed;

llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp

@@ -824,10 +824,7 @@ void SystemZELFFrameLowering::inlineStackProbe(
   StackAllocMI->eraseFromParent();
   if (DoneMBB != nullptr) {
     // Compute the live-in lists for the new blocks.
-    bool anyChange = false;
-    do {
-      anyChange = recomputeLiveIns(*DoneMBB) || recomputeLiveIns(*LoopMBB);
-    } while (anyChange);
+    fullyRecomputeLiveIns({DoneMBB, LoopMBB});
   }
 }
 
@@ -1425,10 +1422,7 @@ void SystemZXPLINKFrameLowering::inlineStackProbe(
   StackAllocMI->eraseFromParent();
 
   // Compute the live-in lists for the new blocks.
-  bool anyChange = false;
-  do {
-    anyChange = recomputeLiveIns(*StackExtMBB) || recomputeLiveIns(*NextMBB);
-  } while (anyChange);
+  fullyRecomputeLiveIns({StackExtMBB, NextMBB});
 }
 
 bool SystemZXPLINKFrameLowering::hasFP(const MachineFunction &MF) const {

llvm/lib/Target/X86/X86FrameLowering.cpp

@@ -885,10 +885,7 @@ void X86FrameLowering::emitStackProbeInlineGenericLoop(
   }
 
   // Update Live In information
-  bool anyChange = false;
-  do {
-    anyChange = recomputeLiveIns(*tailMBB) || recomputeLiveIns(*testMBB);
-  } while (anyChange);
+  fullyRecomputeLiveIns({tailMBB, testMBB});
 }
 
 void X86FrameLowering::emitStackProbeInlineWindowsCoreCLR64(
@@ -1380,11 +1377,7 @@ void X86FrameLowering::BuildStackAlignAND(MachineBasicBlock &MBB,
         footMBB->addSuccessor(&MBB);
       }
 
-      bool anyChange = false;
-      do {
-        anyChange = recomputeLiveIns(*footMBB) || recomputeLiveIns(*bodyMBB) ||
-                    recomputeLiveIns(*headMBB) || recomputeLiveIns(MBB);
-      } while (anyChange);
+      fullyRecomputeLiveIns({footMBB, bodyMBB, headMBB, &MBB});
     }
   } else {
     MachineInstr *MI = BuildMI(MBB, MBBI, DL, TII.get(AndOp), Reg)