fix: Handle mixed string casting that plagues optix codegen (#1718)

The string situation is still a bit tricky on the OptiX side.  There's
a full overhaul of that coming separately as we continue to shift to
an all-ustringhash world.

But in the mean time, we were getting some testsuite failures that
were because of a mismatch between times we think of a gpu-side
ustring as a char* and when it's a uint64. IN FACT, they are always
the hashes, but we backed ourselves into a corner where sometimes that
64 bit pattern is passed around as a pointer, ugh.

This small patch attempts to catch this case and just do the
appropriate cast to compensate. It's a band-aid, a more comprehensive
fix is coming, as I said.

This gets us down to just ONE filing optix test case, which I will
tackle separately.

Signed-off-by: Larry Gritz <lg@larrygritz.com>

---------

Signed-off-by: Larry Gritz <lg@larrygritz.com>

src/include/OSL/llvm_util.h

@@ -762,6 +762,10 @@ public:
     /// return the llvm::Value of the new pointer.
     llvm::Value* int_to_ptr_cast(llvm::Value* val);
 
+    /// Cast the pointer specified by ptr to an int64, return the llvm::Value
+    /// of the new value.
+    llvm::Value* ptr_to_int64_cast(llvm::Value* ptr);
+
     /// Cast the pointer variable specified by val to a pointer of type
     /// void* return the llvm::Value of the new pointer.
     llvm::Value* void_ptr(llvm::Value* val, const std::string& llname = {});

src/liboslexec/backendllvm.cpp

@@ -665,6 +665,13 @@ BackendLLVM::llvm_store_value(llvm::Value* new_val, llvm::Value* dst_ptr,
         dst_ptr = ll.GEP(dst_ptr, 0, component);
 
     // Finally, store the value.
+    if (t == TypeString && dst_ptr->getType() == ll.type_int64_ptr()
+        && new_val->getType() == ll.type_char_ptr()) {
+        // Special case: we are still ickily storing strings sometimes as a
+        // char* and sometimes as a uint64. Do a little sneaky conversion
+        // here.
+        new_val = ll.ptr_to_int64_cast(new_val);
+    }
     ll.op_store(new_val, dst_ptr);
     return true;
 }

src/liboslexec/llvm_util.cpp

@@ -3429,6 +3429,14 @@ LLVM_Util::int_to_ptr_cast(llvm::Value* val)
 
 
 
+llvm::Value*
+LLVM_Util::ptr_to_int64_cast(llvm::Value* ptr)
+{
+    return builder().CreatePtrToInt(ptr, type_int64());
+}
+
+
+
 llvm::Value*
 LLVM_Util::void_ptr(llvm::Value* val, const std::string& llname)
 {
@@ -5216,6 +5224,7 @@ LLVM_Util::op_store(llvm::Value* val, llvm::Value* ptr)
         std::cerr << "op_store val->getType()=" << std::flush;
         val->getType()->print(llvm::errs());
         std::cerr << std::endl;
+        OSL_DASSERT(0 && "We should not have a pointer type mismatch here");
     }
     if (m_mask_stack.empty() || val->getType()->isVectorTy() == false
         || (!is_masking_required())) {