[AMDGPU] Refactor code for GETPC bundle updates in hazards (NFCI)

As suggested in review for PR #100067.
Refactor code for S_GETPC_B64 bundle updates for use with multiple
hazard mitigations.

Author: perlfu

llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp

@@ -2851,6 +2851,38 @@ bool GCNHazardRecognizer::ShouldPreferAnother(SUnit *SU) {
   return false;
 }
 
+// Adjust global offsets for instructions bundled with S_GETPC_B64 after
+// insertion of a new instruction.
+static void updateGetPCBundle(MachineInstr *NewMI) {
+  if (!NewMI->isBundled())
+    return;
+
+  // Find start of bundle.
+  auto I = NewMI->getIterator();
+  while (I->isBundledWithPred())
+    I--;
+  if (I->isBundle())
+    I++;
+
+  // Bail if this is not an S_GETPC bundle.
+  if (I->getOpcode() != AMDGPU::S_GETPC_B64)
+    return;
+
+  // Update offsets of any references in the bundle.
+  const unsigned NewBytes = 4;
+  assert(NewMI->getOpcode() == AMDGPU::S_WAITCNT_DEPCTR &&
+         "Unexpected instruction insertion in bundle");
+  auto NextMI = std::next(NewMI->getIterator());
+  auto End = NewMI->getParent()->end();
+  while (NextMI != End && NextMI->isBundledWithPred()) {
+    for (auto &Operand : NextMI->operands()) {
+      if (Operand.isGlobal())
+        Operand.setOffset(Operand.getOffset() + NewBytes);
+    }
+    NextMI++;
+  }
+}
+
 bool GCNHazardRecognizer::fixVALUMaskWriteHazard(MachineInstr *MI) {
   if (!ST.hasVALUMaskWriteHazard())
     return false;
@@ -2968,22 +3000,12 @@ bool GCNHazardRecognizer::fixVALUMaskWriteHazard(MachineInstr *MI) {
   auto NextMI = std::next(MI->getIterator());
 
   // Add s_waitcnt_depctr sa_sdst(0) after SALU write.
-  BuildMI(*MI->getParent(), NextMI, MI->getDebugLoc(),
-          TII.get(AMDGPU::S_WAITCNT_DEPCTR))
-      .addImm(AMDGPU::DepCtr::encodeFieldSaSdst(0));
+  auto NewMI = BuildMI(*MI->getParent(), NextMI, MI->getDebugLoc(),
+                       TII.get(AMDGPU::S_WAITCNT_DEPCTR))
+                   .addImm(AMDGPU::DepCtr::encodeFieldSaSdst(0));
 
   // SALU write may be s_getpc in a bundle.
-  if (MI->getOpcode() == AMDGPU::S_GETPC_B64) {
-    // Update offsets of any references in the bundle.
-    while (NextMI != MI->getParent()->end() &&
-           NextMI->isBundledWithPred()) {
-      for (auto &Operand : NextMI->operands()) {
-        if (Operand.isGlobal())
-          Operand.setOffset(Operand.getOffset() + 4);
-      }
-      NextMI++;
-    }
-  }
+  updateGetPCBundle(NewMI);
 
   return true;
 }