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

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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
This commit is contained in:
Huan Nguyen 2022-06-10 15:48:13 -07:00 committed by Amir Ayupov
parent e90b56e411
commit 82095bd5ed
3 changed files with 10 additions and 5 deletions
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6
bolt/lib/Core/BinaryContext.cpp
View File

@ -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();

3
bolt/lib/Rewrite/RewriteInstance.cpp
View File

@ -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;
}

6
bolt/test/X86/split-func-icf.s
View File

@ -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