From 842966d5f2921e807ddc348505ee710eba3ad86d Mon Sep 17 00:00:00 2001
From: Martin Nowack <m.nowack@imperial.ac.uk>
Date: Sat, 16 Mar 2019 23:27:20 +0000
Subject: Disable optimisation for functions that contain KLEE calls

Compilers are allowed to hoist function calls and do GVE.
This is currently done even without `--optimization` enabled.

This is unfortunate in the context of KLEE function calls that might
depend on specific code position without direct control flow
dependencies. In such cases, function calls can be hoisted.

To circumvent this, disallow to optimise functions that contain such
calls by default. This might reduce optimisation for some functions
containing such function calls but still allows it for all others.

This patch adds an additional pass, that detects all functions starting with a
prefix `klee_` and disable optimisations for functions containing such
calls.

This is enabled by default but can be disabled by
`--klee-call-optimisation=false`.
---
 lib/Module/OptNone.cpp | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 lib/Module/OptNone.cpp

(limited to 'lib/Module/OptNone.cpp')

diff --git a/lib/Module/OptNone.cpp b/lib/Module/OptNone.cpp
new file mode 100644
index 00000000..08837488
--- /dev/null
+++ b/lib/Module/OptNone.cpp
@@ -0,0 +1,59 @@
+//===-- OptNone.cpp -------------------------------------------------------===//
+//
+//                     The KLEE Symbolic Virtual Machine
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Passes.h"
+
+#include "klee/Config/Version.h"
+
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/Module.h"
+
+namespace klee {
+
+char OptNonePass::ID;
+
+bool OptNonePass::runOnModule(llvm::Module &M) {
+  // Find list of functions that start with `klee_`
+  // and mark all functions that contain such call or invoke as optnone
+  llvm::SmallPtrSet<llvm::Function *,16> CallingFunctions;
+  for (auto &F : M) {
+    if (!F.hasName() || !F.getName().startswith("klee_"))
+      continue;
+#if LLVM_VERSION_CODE >= LLVM_VERSION(3, 5)
+    for (auto *U : F.users()) {
+      // skip non-calls and non-invokes
+      if (!llvm::isa<llvm::CallInst>(U) && !llvm::isa<llvm::InvokeInst>(U))
+        continue;
+      auto *Inst = llvm::cast<llvm::Instruction>(U);
+      CallingFunctions.insert(Inst->getParent()->getParent());
+    }
+#else
+    for (auto i = F.use_begin(), e = F.use_end(); i != e; ++i) {
+      if (auto Inst = llvm::dyn_cast<llvm::Instruction>(*i)) {
+        CallingFunctions.insert(Inst->getParent()->getParent());
+      }
+    }
+#endif
+  }
+
+  bool changed = false;
+  for (auto F : CallingFunctions) {
+    // Skip if already annotated
+    if (F->hasFnAttribute(llvm::Attribute::OptimizeNone))
+      continue;
+    F->addFnAttr(llvm::Attribute::OptimizeNone);
+    F->addFnAttr(llvm::Attribute::NoInline);
+    changed = true;
+  }
+
+  return changed;
+}
+} // namespace klee
-- 
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