Tweak heuristic to limit the maximum cluster size

Author: asb

llvm/lib/Target/RISCV/RISCVInstrInfo.cpp

@@ -2287,8 +2287,9 @@ bool RISCVInstrInfo::shouldClusterMemOps(
   // Assume a cache line size of 64 bytes if no size is set in RISCVSubtarget.
   CacheLineSize = CacheLineSize ? CacheLineSize : 64;
   // Cluster if the memory operations are on the same or a neighbouring cache
-  // line.
-  return std::abs(Offset1 - Offset2) < CacheLineSize;
+  // line, but limit the maximum ClusterSize to avoid creating too much
+  // additional register pressure.
+  return ClusterSize <= 4 && std::abs(Offset1 - Offset2) < CacheLineSize;
 }
 
 // Set BaseReg (the base register operand), Offset (the byte offset being