[Interpreter] Fix out-of-bounds access in ffiInvoke

[eush]

Summary

This commit fixes "attempt to subscript container with out-of-bounds
index" error reported by the GNU C++ Library in debug mode (enabled by
LLVM_ENABLE_EXPENSIVE_CHECKS).

[nicholas]

test/ExecutionEngine/Interpreter/rand.ll

1

This matches the style in intrinsics.ll, but alias.ll uses "%lli -force-interpreter %s", the differences being that it uses %lli instead of lli and does not use < redirection. I do not know which style is correct or preferred.

[eush]

I grepped the code base, and it seems that the style in alias.ll is much
more common, in particular intrinsics.ll is the only test that runs lli with
input redirection, so I changed the test to match the style in alias.ll
instead.

I also renamed the test to better indicate what it is about.

[eush]

test/ExecutionEngine/Interpreter/rand.ll

1

I created https://llvm.org/PR39524 about using lli vs %lli in tests. There is no resolution on that yet.

[eush]

Could you commit this patch on my behalf?

[nicholas]

In D53556#1291564, @eush wrote:

Could you commit this patch on my behalf?

I have been away from the LLVM community for a few years and am not comfortable committing a patch without review from a current committer.

Could someone on llvm-commits please take a look?

[lhames]

LGTM. Committed as r347281. Thanks Eugene!

lib/ExecutionEngine/Interpreter/ExternalFunctions.cpp

for (Function::const_arg_iterator A = F->arg_begin(), E = F->arg_end();
     Type *ArgTy = FTy->getParamType(ArgNo);
     values[ArgNo] = ffiValueFor(ArgTy, ArgVals[ArgNo], ArgDataPtr);
     ArgDataPtr += TD.getTypeStoreSize(ArgTy);
   }
 
   Type *RetTy = FTy->getReturnType();
   ffi_type *rtype = ffiTypeFor(RetTy);
 
-  if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, NumArgs, rtype, &args[0]) == FFI_OK) {
+  if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, NumArgs, rtype, args.data()) ==
+      FFI_OK) {
     SmallVector<uint8_t, 128> ret;
     if (RetTy->getTypeID() != Type::VoidTyID)
       ret.resize(TD.getTypeStoreSize(RetTy));
     ffi_call(&cif, Fn, ret.data(), values.data());
     switch (RetTy->getTypeID()) {
       case Type::IntegerTyID:
         switch (cast<IntegerType>(RetTy)->getBitWidth()) {
           case 8:  Result.IntVal = APInt(8 , *(int8_t *) ret.data()); break;

test/ExecutionEngine/Interpreter/rand.ll

+; RUN: lli -O0 -force-interpreter < %s
+
+declare void @exit(i32)
+declare i32 @rand()
+
+define i32 @main() {
+  %ret = call i32 @rand()
+  call void @exit(i32 0)
+  ret i32 %ret
+}