Merge #1087

1087: Use loop to initialize repeat arrays r=philberty a=dafaust

This PR changes how we compile initializers for arrays of repeating elements. I use the same approach outlined in the comments of the linked issue, with some tweaks. It is very similar to how the D language front-end compiles, the new function `Gcc_backend::array_initializer` is heavily inspired by the D front-end's `build_array_set`

This fixes the issue where the compiler tries to allocate a vec containing all elements of the array to be constructed, and therefore explodes on huge constructions (e.g. `let x = [0u8; 4 * 1024 * 1024 * 1024 * 1024]`)

However, we can only initialize non-const arrays in this way. For arrays in const contexts we must initialize them at compile time, and therefore continue using the old method.

Fixes: #1068 


Co-authored-by: David Faust <david.faust@oracle.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/gcc/rust/backend/rust-compile-item.cc b/gcc/rust/backend/rust-compile-item.cc
index 21cbb1c..80b7ceb 100644
--- a/gcc/rust/backend/rust-compile-item.cc
+++ b/gcc/rust/backend/rust-compile-item.cc
@@ -92,9 +92,11 @@ CompileItem::visit (HIR::ConstantItem &constant)
   rust_assert (ok);
 
   HIR::Expr *const_value_expr = constant.get_expr ();
+  ctx->push_const_context ();
   tree const_expr
     = compile_constant_item (ctx, resolved_type, canonical_path,
 			     const_value_expr, constant.get_locus ());
+  ctx->pop_const_context ();
 
   ctx->push_const (const_expr);
   ctx->insert_const_decl (constant.get_mappings ().get_hirid (), const_expr);