revert making Type{()} a bitstype since this cause ambiguity. also fi…

…x emission of variables in dead code (having type Union())

src/cgutils.cpp

@@ -543,11 +543,6 @@ DLLEXPORT Type *julia_type_to_llvm(jl_value_t *jt)
  }
  return julia_struct_to_llvm(jt);
  }
- if (jl_is_type_type(jt)) {
- jl_value_t *tp = jl_tparam0(jt);
- if (jl_tuple_len(tp) == 0) // Type{()} is a bitstype
- return T_void;
- }
  return jl_pvalue_llvmt;
 }
 }

src/codegen.cpp

@@ -1382,11 +1382,6 @@ static bool is_getfield_nonallocating(jl_datatype_t *ty, jl_value_t *fld)
 
 static bool jltupleisbits(jl_value_t *jt, bool allow_unsized)
 {
- if (jl_is_type_type(jt)) {
- jl_value_t *tp = jl_tparam0(jt);
- if (jl_tuple_len(tp) == 0) // Type{()} is a bitstype
- return true;
- }
  if (!jl_is_tuple(jt))
  return jl_isbits(jt) && jl_is_leaf_type(jt) && (allow_unsized ||
  ((jl_is_bitstype(jt) && jl_datatype_size(jt) > 0) ||
@@ -2839,12 +2834,11 @@ static Value *emit_var(jl_sym_t *sym, jl_value_t *ty, jl_codectx_t *ctx, bool is
 static Value* emit_assignment(Value *bp, jl_value_t *r, jl_value_t *declType, bool isVolatile, bool used, jl_codectx_t *ctx) {
  Value *rval;
  jl_value_t *rt = expr_type(r,ctx);
- if ((jl_is_symbol(r) || jl_is_symbolnode(r)) && rt == jl_bottom_type) {
- // sometimes x = y::Union() occurs
- if (builder.GetInsertBlock()->getTerminator() != NULL)
- return NULL;
- }
  if (bp != NULL) {
+ if ((jl_is_symbol(r) || jl_is_symbolnode(r) || jl_is_gensym(r)) && rt == jl_bottom_type) {
+ // sometimes x = y::Union() occurs
+ return UndefValue::get(bp->getType()->getContainedType(0));
+ }
  Type *vt = bp->getType();
  if (vt != jl_ppvalue_llvmt) { // unboxed store (in an alloca)
  // `rt` is technically correct here, but sometimes we're not propagating type information
@@ -2866,8 +2860,12 @@ static Value* emit_assignment(Value *bp, jl_value_t *r, jl_value_t *declType, bo
  }
  else {
  rval = emit_expr(r, ctx, true);
- if (!used)
- return NULL;
+
+ // don't need to store this if it isn't used
+ // and sometimes we can get x::Union() = Expr(:tuple)::() in dead code
+ if (!used || declType == jl_bottom_type)
+ return UndefValue::get(rval->getType());
+
  // Make sure this is already boxed. If not, there was
  // something wrong in the earlier analysis as this should
  // have been alloca'd
@@ -2905,14 +2903,6 @@ static void emit_assignment(jl_value_t *l, jl_value_t *r, jl_codectx_t *ctx)
  else {
  jl_varinfo_t &vi = ctx->vars[s];
  Value *rval = emit_assignment(bp, r, vi.declType, vi.isVolatile, vi.used, ctx);
- if (rval == NULL) return; // don't actually do the assignment if the var is never read
-
- if (builder.GetInsertBlock()->getTerminator() == NULL) {
- jl_arrayvar_t *av = arrayvar_for(l, ctx);
- if (av != NULL) {
- assign_arrayvar(*av, rval);
- }
- }
 
  if (vi.isSA &&
  ((bp == NULL) ||
@@ -2921,6 +2911,13 @@ static void emit_assignment(jl_value_t *l, jl_value_t *r, jl_codectx_t *ctx)
  // use SSA value instead of GC frame load for var access
  vi.SAvalue = rval;
  }
+
+ if (!isa<UndefValue>(rval) && builder.GetInsertBlock()->getTerminator() == NULL) {
+ jl_arrayvar_t *av = arrayvar_for(l, ctx);
+ if (av != NULL) {
+ assign_arrayvar(*av, rval);
+ }
+ }
  }
 }
 
@@ -4171,7 +4168,9 @@ static Function *emit_function(jl_lambda_info_t *lam, bool cstyle)
  vi.passedAs = NULL;
  }
  else {
- vi.isGhost = false;
+ // this might happen if the arg is also used as a local variable or
+ // if the argument being passed is an empty tuple since ()::Type{()}
+ //vi.isGhost = false;
  //vi.passedAs = ???; //XXX
  //builder.CreateStore(???,vi.memvalue); //XXX
  }