Core/Executor: Fix unaligned write of fp80 arguments

... in Executor::callExternalFunction.

Fixes the following error reported in Feature/VarArg{Alignment,LongDouble}.c
tests:

lib/Expr/Expr.cpp:366:5: runtime error: store to misaligned address
    0x7ffc011d3528 for type 'long double', which requires 16 byte alignment

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/Core/Executor.cpp b/lib/Core/Executor.cpp
index c50e4520..85413a42 100644
--- a/lib/Core/Executor.cpp
+++ b/lib/Core/Executor.cpp
@@ -3881,6 +3881,10 @@ void Executor::callExternalFunction(ExecutionState &state,
     } else {
       ref<Expr> arg = toUnique(state, *ai);
       if (ConstantExpr *ce = dyn_cast<ConstantExpr>(arg)) {
+        // fp80 must be aligned to 16 according to the System V AMD 64 ABI
+        if (ce->getWidth() == Expr::Fl80 && wordIndex & 0x01)
+          wordIndex++;
+
         // XXX kick toMemory functions from here
         ce->toMemory(&args[wordIndex]);
         wordIndex += (ce->getWidth()+63)/64;