[llvm] [BOLT] Run PatchEntries pass before LongJmp (PR #137236)

[Maksim Panchenko via llvm-commits]

https://github.com/maksfb created https://github.com/llvm/llvm-project/pull/137236

With --force-patch option, every original function entry point is overwritten with a trampoline to a new version of the function to prevent the execution of the original code.

If the function size is too small for the trampoline code, we are forced to bail out on rewriting the function. That presented a problem on AArch64 due to LongJmp pass that assumed the presence of the new copy of the function. If the new copy was not emitted it could have lead to a relocation overflow.

Run PatchEntries pass before LongJmp and make the latter aware of the functions that are not going to be emitted. Make --force-patch option behavior on AArch64 consistent with other architectures.

>From b747548c33e976be92669e41d5cac54f8b0e4c8d Mon Sep 17 00:00:00 2001
From: Maksim Panchenko <maks at fb.com>
Date: Wed, 23 Apr 2025 15:26:18 -0700
Subject: [PATCH] [BOLT] Run PatchEntries pass before LongJmp

With --force-patch option, every original function entry point is
overwritten with a trampoline to a new version of the function to
prevent the execution of the original code.

If the function size is too small for the trampoline code, we are forced
to bail out on rewriting the function. That presented a problem on
AArch64 due to LongJmp pass that assumed the presence of the new copy of
the function. If the new copy was not emitted it could have lead to a
relocation overflow.

Run PatchEntries pass before LongJmp and make the latter aware of the
functions that are not going to be emitted. Make --force-patch option
behavior on AArch64 consistent with other architectures.
---
 bolt/lib/Passes/PatchEntries.cpp       | 13 +------------
 bolt/lib/Rewrite/BinaryPassManager.cpp |  8 ++++----
 2 files changed, 5 insertions(+), 16 deletions(-)

diff --git a/bolt/lib/Passes/PatchEntries.cpp b/bolt/lib/Passes/PatchEntries.cpp
index 8a2f0a39a56cc..4877e7dd8fdf3 100644
--- a/bolt/lib/Passes/PatchEntries.cpp
+++ b/bolt/lib/Passes/PatchEntries.cpp
@@ -98,21 +98,10 @@ Error PatchEntries::runOnFunctions(BinaryContext &BC) {
     });
 
     if (!Success) {
-      // We can't change output layout for AArch64 due to LongJmp pass
-      if (BC.isAArch64()) {
-        if (opts::ForcePatch) {
-          BC.errs() << "BOLT-ERROR: unable to patch entries in " << Function
-                    << "\n";
-          return createFatalBOLTError("");
-        }
-
-        continue;
-      }
-
       // If the original function entries cannot be patched, then we cannot
       // safely emit new function body.
       BC.errs() << "BOLT-WARNING: failed to patch entries in " << Function
-                << ". The function will not be optimized.\n";
+                << ". The function will not be optimized\n";
       Function.setIgnored();
       continue;
     }
diff --git a/bolt/lib/Rewrite/BinaryPassManager.cpp b/bolt/lib/Rewrite/BinaryPassManager.cpp
index dd48653931eb9..996d2e972599d 100644
--- a/bolt/lib/Rewrite/BinaryPassManager.cpp
+++ b/bolt/lib/Rewrite/BinaryPassManager.cpp
@@ -497,6 +497,10 @@ Error BinaryFunctionPassManager::runAllPasses(BinaryContext &BC) {
   // memory profiling data.
   Manager.registerPass(std::make_unique<ReorderData>());
 
+  // Patch original function entries
+  if (BC.HasRelocations)
+    Manager.registerPass(std::make_unique<PatchEntries>());
+
   if (BC.isAArch64()) {
     Manager.registerPass(
         std::make_unique<ADRRelaxationPass>(PrintAdrRelaxation));
@@ -524,10 +528,6 @@ Error BinaryFunctionPassManager::runAllPasses(BinaryContext &BC) {
   // Assign each function an output section.
   Manager.registerPass(std::make_unique<AssignSections>());
 
-  // Patch original function entries
-  if (BC.HasRelocations)
-    Manager.registerPass(std::make_unique<PatchEntries>());
-
   // This pass turns tail calls into jumps which makes them invisible to
   // function reordering. It's unsafe to use any CFG or instruction analysis
   // after this point.