codegen: handle dead code with unsafe_store of FCA pointers (#50164)

Fix #50125

Author: vtjnash

src/intrinsics.cpp

@@ -695,7 +695,7 @@ static jl_cgval_t emit_pointerref(jl_codectx_t &ctx, jl_cgval_t *argv)
         ai.decorateInst(load);
         return mark_julia_type(ctx, load, true, ety);
     }
-    else if (!jl_isbits(ety)) {
+    else if (!deserves_stack(ety)) {
         assert(jl_is_datatype(ety));
         uint64_t size = jl_datatype_size(ety);
         Value *strct = emit_allocobj(ctx, (jl_datatype_t*)ety);
@@ -716,7 +716,7 @@ static jl_cgval_t emit_pointerref(jl_codectx_t &ctx, jl_cgval_t *argv)
         assert(!isboxed);
         if (!type_is_ghost(ptrty)) {
             Value *thePtr = emit_unbox(ctx, ptrty->getPointerTo(), e, e.typ);
-            auto load = typed_load(ctx, thePtr, im1, ety, ctx.tbaa().tbaa_data, nullptr, isboxed, AtomicOrdering::NotAtomic, true, align_nb);
+            auto load = typed_load(ctx, thePtr, im1, ety, ctx.tbaa().tbaa_data, nullptr, isboxed, AtomicOrdering::NotAtomic, false, align_nb);
             setName(ctx.emission_context, load.V, "pointerref");
             return load;
         }
@@ -775,7 +775,7 @@ static jl_cgval_t emit_pointerset(jl_codectx_t &ctx, jl_cgval_t *argv)
         jl_aliasinfo_t ai = jl_aliasinfo_t::fromTBAA(ctx, ctx.tbaa().tbaa_data);
         ai.decorateInst(store);
     }
-    else if (!jl_isbits(ety)) {
+    else if (x.ispointer()) {
         thePtr = emit_unbox(ctx, getInt8PtrTy(ctx.builder.getContext()), e, e.typ);
         uint64_t size = jl_datatype_size(ety);
         im1 = ctx.builder.CreateMul(im1, ConstantInt::get(ctx.types().T_size,
@@ -852,7 +852,7 @@ static jl_cgval_t emit_atomic_pointerref(jl_codectx_t &ctx, jl_cgval_t *argv)
         return jl_cgval_t();
     }
 
-    if (!jl_isbits(ety)) {
+    if (!deserves_stack(ety)) {
         assert(jl_is_datatype(ety));
         Value *strct = emit_allocobj(ctx, (jl_datatype_t*)ety);
         setName(ctx.emission_context, strct, "atomic_pointerref_box");
@@ -876,7 +876,7 @@ static jl_cgval_t emit_atomic_pointerref(jl_codectx_t &ctx, jl_cgval_t *argv)
         assert(!isboxed);
         if (!type_is_ghost(ptrty)) {
             Value *thePtr = emit_unbox(ctx, ptrty->getPointerTo(), e, e.typ);
-            auto load = typed_load(ctx, thePtr, nullptr, ety, ctx.tbaa().tbaa_data, nullptr, isboxed, llvm_order, true, nb);
+            auto load = typed_load(ctx, thePtr, nullptr, ety, ctx.tbaa().tbaa_data, nullptr, isboxed, llvm_order, false, nb);
             setName(ctx.emission_context, load.V, "atomic_pointerref");
             return load;
         }
@@ -954,6 +954,7 @@ static jl_cgval_t emit_atomic_pointerop(jl_codectx_t &ctx, intrinsic f, const jl
     }
 
     if (!jl_isbits(ety)) {
+        //if (!deserves_stack(ety))
         //Value *thePtr = emit_unbox(ctx, getInt8PtrTy(ctx.builder.getContext()), e, e.typ);
         //uint64_t size = jl_datatype_size(ety);
         return emit_runtime_call(ctx, f, argv, nargs); // TODO: optimizations