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`.

1 files changed, 8 insertions, 0 deletions

diff --git a/lib/Module/Passes.h b/lib/Module/Passes.h
index 417ebe7d..6a302819 100644
--- a/lib/Module/Passes.h
+++ b/lib/Module/Passes.h
@@ -185,6 +185,14 @@ public:
   bool runOnModule(llvm::Module &M) override;
 };
 #endif
+
+/// Instruments every function that contains a KLEE function call as nonopt
+class OptNonePass : public llvm::ModulePass {
+public:
+  static char ID;
+  OptNonePass() : llvm::ModulePass(ID) {}
+  bool runOnModule(llvm::Module &M) override;
+};
 } // namespace klee
 
 #endif