[BOLT] Mark fragments related to split jump table as non-simple

Mark fragments related to split jump table as non-simple.

A function could be splitted into hot and cold fragments. A split jump table is
challenging for correctly reconstructing control flow graphs, so it was marked
as ignored. This update marks those fragments as non-simple, allowing them
to be printed and partial control flow graph construction.

Test Plan:
```
llvm-lit -a tools/bolt/test/X86/split-func-icf.s
```
This test has two functions (main, main2), each has a jump table target to the
same cold portion main2.cold.1(*2). We try to print out only this cold portion.
If it is ignored, it cannot be printed. If it is non-simple, it can be printed. We
verify that it can be printed.

Reviewed By: Amir

Differential Revision: https://reviews.llvm.org/D127464

diff --git a/bolt/lib/Core/BinaryContext.cpp b/bolt/lib/Core/BinaryContext.cpp
index f5fc26d..db66a73 100644 (file)
--- a/bolt/lib/Core/BinaryContext.cpp
+++ b/bolt/lib/Core/BinaryContext.cpp
@@ -715,13 +715,15 @@ void BinaryContext::skipMarkedFragments() {
            "internal error in traversing function fragments");
     if (opts::Verbosity >= 1)
       errs() << "BOLT-WARNING: Ignoring " << BF->getPrintName() << '\n';
-    BF->setIgnored();
+    BF->setSimple(false);
+    BF->setHasSplitJumpTable(true);
+
     std::for_each(BF->Fragments.begin(), BF->Fragments.end(), addToWorklist);
     std::for_each(BF->ParentFragments.begin(), BF->ParentFragments.end(),
                   addToWorklist);
   }
   if (!FragmentsToSkip.empty())
-    errs() << "BOLT-WARNING: ignored " << FragmentsToSkip.size() << " function"
+    errs() << "BOLT-WARNING: skipped " << FragmentsToSkip.size() << " function"
            << (FragmentsToSkip.size() == 1 ? "" : "s")
            << " due to cold fragments\n";
   FragmentsToSkip.clear();

diff --git a/bolt/lib/Rewrite/RewriteInstance.cpp b/bolt/lib/Rewrite/RewriteInstance.cpp
index b4e9613..41055d2 100644 (file)
--- a/bolt/lib/Rewrite/RewriteInstance.cpp
+++ b/bolt/lib/Rewrite/RewriteInstance.cpp
@@ -2925,7 +2925,8 @@ void RewriteInstance::disassembleFunctions() {
       continue;
 
     if (!Function.isSimple()) {
-      assert((!BC->HasRelocations || Function.getSize() == 0) &&
+      assert((!BC->HasRelocations || Function.getSize() == 0 ||
+              Function.hasSplitJumpTable()) &&
              "unexpected non-simple function in relocation mode");
       continue;
     }

diff --git a/bolt/test/X86/split-func-icf.s b/bolt/test/X86/split-func-icf.s
index 00fe628..eac4174 100644 (file)
--- a/bolt/test/X86/split-func-icf.s
+++ b/bolt/test/X86/split-func-icf.s
@@ -8,15 +8,17 @@
 # RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown %s -o %t.o
 # RUN: llvm-strip --strip-unneeded %t.o
 # RUN: %clang %cflags %t.o -o %t.exe -Wl,-q
-# RUN: llvm-bolt %t.exe -o %t.out -lite=0 -v=1 2>&1 | FileCheck %s
+# RUN: llvm-bolt %t.exe -o %t.out -v=1 --print-only=main2.cold.1 --print-disasm 2>&1 | FileCheck %s
 
 # CHECK-NOT: unclaimed PC-relative relocations left in data
 # CHECK-DAG: BOLT-INFO: marking main2.cold.1(*2) as a fragment of main
 # CHECK-DAG: BOLT-INFO: marking main2.cold.1(*2) as a fragment of main2
+# CHECK: Binary Function "main2.cold.1(*2)" after disassembly
+# CHECK: End of Function "main2.cold.1(*2)"
 # CHECK-DAG: BOLT-WARNING: Ignoring main2
 # CHECK-DAG: BOLT-WARNING: Ignoring main
 # CHECK-DAG: BOLT-WARNING: Ignoring main2.cold.1(*2)
-# CHECK: BOLT-WARNING: ignored 3 functions due to cold fragments
+# CHECK: BOLT-WARNING: skipped 3 functions due to cold fragments
   .text
   .globl main
   .type main, %function