[CodeGen] Introduce Static Data Splitter pass (#122183)

https://discourse.llvm.org/t/rfc-profile-guided-static-data-partitioning/83744
proposes to partition static data sections.

This patch introduces a codegen pass. This patch produces jump table
hotness in the in-memory states (machine jump table info and entries).
Target-lowering and asm-printer consume the states and produce `.hot`
section suffix. The follow up PR
https://github.com/llvm/llvm-project/pull/122215 implements such
changes.

---------

Co-authored-by: Ellis Hoag <ellis.sparky.hoag@gmail.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineFunction.cpp b/llvm/lib/CodeGen/MachineFunction.cpp
index b8dbe83..e482418 100644
--- a/llvm/lib/CodeGen/MachineFunction.cpp
+++ b/llvm/lib/CodeGen/MachineFunction.cpp
@@ -1311,6 +1311,10 @@ const unsigned MachineFunction::DebugOperandMemNumber = 1000000;
 //  MachineJumpTableInfo implementation
 //===----------------------------------------------------------------------===//
 
+MachineJumpTableEntry::MachineJumpTableEntry(
+    const std::vector<MachineBasicBlock *> &MBBs)
+    : MBBs(MBBs), Hotness(MachineFunctionDataHotness::Unknown) {}
+
 /// Return the size of each entry in the jump table.
 unsigned MachineJumpTableInfo::getEntrySize(const DataLayout &TD) const {
   // The size of a jump table entry is 4 bytes unless the entry is just the
@@ -1360,6 +1364,17 @@ unsigned MachineJumpTableInfo::createJumpTableIndex(
   return JumpTables.size()-1;
 }
 
+bool MachineJumpTableInfo::updateJumpTableEntryHotness(
+    size_t JTI, MachineFunctionDataHotness Hotness) {
+  assert(JTI < JumpTables.size() && "Invalid JTI!");
+  // Record the largest hotness value.
+  if (Hotness <= JumpTables[JTI].Hotness)
+    return false;
+
+  JumpTables[JTI].Hotness = Hotness;
+  return true;
+}
+
 /// If Old is the target of any jump tables, update the jump tables to branch
 /// to New instead.
 bool MachineJumpTableInfo::ReplaceMBBInJumpTables(MachineBasicBlock *Old,