[PATCH] D155156: [BOLT] Attach ORC info to instructions in CFG

[Maksim Panchenko via Phabricator via llvm-commits]

maksfb created this revision.
maksfb added reviewers: treapster, jobnoorman, yota9, Amir, ayermolo, rafauler.
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Propagate Linux Kernel ORC information read from the file to the whole
function CFG once the graph has been built. We have a choice to either
attach ORC state annotation to every instruction, or to the first
instruction in the basic block to conserve processing memory. I chose to
attach to every instruction under --print-orc option which is currently
on by default.

Depends on D155153 <https://reviews.llvm.org/D155153>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D155156

Files:
  bolt/lib/Rewrite/LinuxKernelRewriter.cpp


Index: bolt/lib/Rewrite/LinuxKernelRewriter.cpp
===================================================================
--- bolt/lib/Rewrite/LinuxKernelRewriter.cpp
+++ bolt/lib/Rewrite/LinuxKernelRewriter.cpp
@@ -114,6 +114,9 @@
   /// Read ORC unwind information and annotate instructions.
   Error readORCTables();
 
+  /// Update ORC for functions once CFG is constructed.
+  Error processORCPostCFG();
+
   /// Update ORC data in the binary.
   Error rewriteORCTables();
 
@@ -135,6 +138,13 @@
     return Error::success();
   }
 
+  Error postCFGInitializer() override {
+    if (Error E = processORCPostCFG())
+      return E;
+
+    return Error::success();
+  }
+
   Error postEmitFinalizer() override {
     updateLKMarkers();
 
@@ -512,6 +522,41 @@
   return Error::success();
 }
 
+Error LinuxKernelRewriter::processORCPostCFG() {
+  // Propagate ORC to the rest of the function. We can annotate every
+  // instruction in every function, but to minimize the overhead, we annotate
+  // the first // instruction in every basic block to reflect the state at the
+  // entry. This way, the ORC state can be calculated based on annotations
+  // regardless of the basic block layout. Note that if we insert/delete
+  // instructions, we must take care to attach ORC info to the new/deleted ones.
+  for (BinaryFunction &BF : llvm::make_second_range(BC.getBinaryFunctions())) {
+    if (!BF.hasORC())
+      continue;
+
+    std::optional<ORCState> CurrentState;
+    for (BinaryBasicBlock &BB : BF) {
+      for (MCInst &Inst : BB) {
+        ErrorOr<ORCState> State =
+            BC.MIB->tryGetAnnotationAs<ORCState>(Inst, "ORC");
+
+        if (State) {
+          CurrentState = *State;
+          continue;
+        }
+
+        if (!CurrentState)
+          continue;
+
+        // While printing ORC, attach info to every instruction for convenience.
+        if (opts::PrintORC || &Inst == &BB.front())
+          BC.MIB->addAnnotation(Inst, "ORC", *CurrentState);
+      }
+    }
+  }
+
+  return Error::success();
+}
+
 Error LinuxKernelRewriter::rewriteORCTables() {
   // TODO:
   return Error::success();


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