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From: Thomas Schwinge <tschwinge@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc/devel/rust/master] transmute: Fix behavior by always performing the raw copy Date: Thu, 11 Aug 2022 19:19:11 +0000 (GMT) [thread overview] Message-ID: <20220811191911.88C8D3857BAB@sourceware.org> (raw) https://gcc.gnu.org/g:71b5bc8705c789fa61ad0d7858441da861213356 commit 71b5bc8705c789fa61ad0d7858441da861213356 Author: Arthur Cohen <arthur.cohen@embecosm.com> Date: Tue Aug 9 13:50:39 2022 +0200 transmute: Fix behavior by always performing the raw copy This desugars calls to transmute the following way: `transmute::<T1, T2>(value)` -> `*((T2 *) &value)` This always ends up being optimized into a simple copy for small types and a memcpy for larger types. Co-authored-by: philberty <philip.herron@embecosm.com> Diff: --- gcc/rust/backend/rust-compile-intrinsic.cc | 36 ++++++------------------ gcc/testsuite/rust/execute/torture/transmute1.rs | 23 +++++++++++++++ 2 files changed, 32 insertions(+), 27 deletions(-) diff --git a/gcc/rust/backend/rust-compile-intrinsic.cc b/gcc/rust/backend/rust-compile-intrinsic.cc index ebf1ed61f55..75e8c99158b 100644 --- a/gcc/rust/backend/rust-compile-intrinsic.cc +++ b/gcc/rust/backend/rust-compile-intrinsic.cc @@ -390,33 +390,15 @@ transmute_intrinsic_handler (Context *ctx, TyTy::BaseType *fntype_tyty) ctx->push_block (code_block); // BUILTIN transmute FN BODY BEGIN - tree result_type_tree = TREE_TYPE (DECL_RESULT (fndecl)); - tree result_expr = error_mark_node; - if (AGGREGATE_TYPE_P (TREE_TYPE (convert_me_expr))) - { - // Return *(orig_type*)&decl. */ - // tree t = build_fold_addr_expr_loc (location.gcc_location (), this->t_); - // t = fold_build1_loc (location.gcc_location (), NOP_EXPR, - // build_pointer_type (this->orig_type_), t); - // return build_fold_indirect_ref_loc (location.gcc_location (), t); - - // result_expr = fold_build1_loc (Location ().gcc_location (), - // CONVERT_EXPR, - // result_type_tree, convert_me_expr); - - tree t = build_fold_addr_expr_loc (Location ().gcc_location (), - convert_me_expr); - t = fold_build1_loc (Location ().gcc_location (), NOP_EXPR, - build_pointer_type (target_type_expr), t); - result_expr - = build_fold_indirect_ref_loc (Location ().gcc_location (), t); - } - else - { - result_expr = ctx->get_backend ()->convert_expression (result_type_tree, - convert_me_expr, - Location ()); - } + + // Return *((orig_type*)&decl) */ + + tree t + = build_fold_addr_expr_loc (Location ().gcc_location (), convert_me_expr); + t = fold_build1_loc (Location ().gcc_location (), NOP_EXPR, + build_pointer_type (target_type_expr), t); + tree result_expr + = build_fold_indirect_ref_loc (Location ().gcc_location (), t); auto return_statement = ctx->get_backend ()->return_statement (fndecl, {result_expr}, diff --git a/gcc/testsuite/rust/execute/torture/transmute1.rs b/gcc/testsuite/rust/execute/torture/transmute1.rs new file mode 100644 index 00000000000..b9ec38ca618 --- /dev/null +++ b/gcc/testsuite/rust/execute/torture/transmute1.rs @@ -0,0 +1,23 @@ +// { dg-additional-options "-w" } + +extern "rust-intrinsic" { + fn transmute<T, U>(value: T) -> U; +} + +struct WrapI { + inner: i32, +} + +struct WrapF { + inner: f32, +} + +fn main() -> i32 { + let f = 15.4f32; + let f_wrap = WrapF { inner: f }; + + let fst = unsafe { transmute::<f32, i32>(f) }; + let snd = unsafe { transmute::<WrapF, WrapI>(f_wrap) }; + + fst - snd.inner +}
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