[CodeGen][StaticDataPartitioning]Place local-linkage global variables in hot or unlikely prefixed sections based on profile information (#125756)

In this PR, static-data-splitter pass finds out the local-linkage global
variables in {`.rodata`, `.data.rel.ro`, `bss`, `.data`} sections by
analyzing machine instruction operands, and aggregates their accesses
from code across functions.

A follow-up item is to analyze global variable initializers and count
for access from data.
* This limitation is demonstrated by `bss2` and `data3` in
`llvm/test/CodeGen/X86/global-variable-partition.ll`.

Some stats of static-data-splitter with this patch:

**section**|**bss**|**rodata**|**data**
:-----:|:-----:|:-----:|:-----:
hot-prefixed section coverage|99.75%|97.71%|91.30%
unlikely-prefixed section size percentage|67.94%|39.37%|63.10%

1. The coverage is defined as `#perf-sample-in-hot-prefixed <data>
section / #perf-sample in <data.*> section` for each <data> section.
* The perf command samples
`MEM_INST_RETIRED.ALL_LOADS:u:pinned:precise=2` events at a high
frequency (`perf -c 2251`) for 30 seconds. The profiled binary is built
as non-PIE so `data.rel.ro` coverage data is not available.
2. The unlikely-prefixed `<data>` section size percentage is defined as
`unlikely <data> section size / the sum size of <data>.* sections` for
each `<data>` section

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/TargetPassConfig.cpp b/llvm/lib/CodeGen/TargetPassConfig.cpp
index f788ec5..fa1bb84 100644
--- a/llvm/lib/CodeGen/TargetPassConfig.cpp
+++ b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -1257,8 +1257,13 @@ void TargetPassConfig::addMachinePasses() {
       }
     }
     addPass(createMachineFunctionSplitterPass());
-    if (SplitStaticData || TM->Options.EnableStaticDataPartitioning)
+    if (SplitStaticData || TM->Options.EnableStaticDataPartitioning) {
+      // The static data splitter pass is a machine function pass. and
+      // static data annotator pass is a module-wide pass. See the file comment
+      // in StaticDataAnnotator.cpp for the motivation.
       addPass(createStaticDataSplitterPass());
+      addPass(createStaticDataAnnotatorPass());
+    }
   }
   // We run the BasicBlockSections pass if either we need BB sections or BB
   // address map (or both).