Replace assertions of types on LLVM instructions in the Executor with a

pass that checks these assertions. This improves several things.

* This pass provides more friendly messages than assertions in that it
just emits a warning and carries on checking the rest of the
instructions.

* The takes the checks outside of the Executor's hot path and so avoids
checking the same instruction multiple times. Now each instruction
is only checked once just before execution starts.

The disadvantage of this approach is the check for invariants we expect
to hold have been pulled far away from where we expect them to hold.
After discussion with @ccadar and @MartinNowack it was decided we will
take this hit to readability for better performance and simpler code in
the Executor.

1 files changed, 17 insertions, 0 deletions

diff --git a/lib/Module/Passes.h b/lib/Module/Passes.h
index 293766c1..2ac57b9b 100644
--- a/lib/Module/Passes.h
+++ b/lib/Module/Passes.h
@@ -189,6 +189,23 @@ private:
 llvm::FunctionPass *createScalarizerPass();
 #endif
 
+/// InstructionOperandTypeCheckPass - Type checks the types of instruction
+/// operands to check that they conform to invariants expected by the Executor.
+///
+/// This is a ModulePass because other pass types are not meant to maintain
+/// state between calls.
+class InstructionOperandTypeCheckPass : public llvm::ModulePass {
+private:
+  bool instructionOperandsConform;
+
+public:
+  static char ID;
+  InstructionOperandTypeCheckPass()
+      : llvm::ModulePass(ID), instructionOperandsConform(true) {}
+  // TODO: Add `override` when we switch to C++11
+  bool runOnModule(llvm::Module &M);
+  bool checkPassed() const { return instructionOperandsConform; }
+};
 }
 
 #endif