[gccrs,COMMIT] gccrs: Evaluate non-unit tail expressions before drops
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Commit Message
From: Lishin <lishin1008@gmail.com>
A non-unit tail call could run after local drops. Store the tail expression
result before emitting drops, then return the stored value.
gcc/rust/ChangeLog:
* backend/rust-compile-base.cc
(HIRCompileBase::compile_function_body): Store non-unit tail expression
results before emitting current scope drops.
gcc/testsuite/ChangeLog:
* rust/execute/drop-function-scope-non-unit-tail.rs: New test.
Signed-off-by: Lishin <lishin1008@gmail.com>
---
This change was merged into the gccrs repository and is posted here for
upstream visibility and potential drive-by review, as requested by GCC
release managers.
Each commit email contains a link to its details on github from where you can
find the Pull-Request and associated discussions.
Commit on github: https://github.com/Rust-GCC/gccrs/commit/99edb212c204385d994c72b85e8098be6f464226
The commit has NOT been mentioned in any issue.
The commit has been mentioned in the following pull-request(s):
- https://github.com/Rust-GCC/gccrs/pull/4602
gcc/rust/backend/rust-compile-base.cc | 22 ++++++++-
.../drop-function-scope-non-unit-tail.rs | 46 +++++++++++++++++++
2 files changed, 67 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/rust/execute/drop-function-scope-non-unit-tail.rs
base-commit: 25ab7ba2877cec8bb831ddfeea9ecb72ef23c9d5
@@ -708,10 +708,30 @@ HIRCompileBase::compile_function_body (tree fndecl,
return_value = coercion_site (id, return_value, actual, expected,
lvalue_locus, rvalue_locus);
+ /* Save the non-unit tail expression result before emitting scope
+ drops, so a tail call like foo() is evaluated before locals are
+ dropped. Conceptually, this changes lowering from:
+
+ drop (_x);
+ return foo ();
+
+ to:
+
+ ret_slot = foo ();
+ drop (_x);
+ return ret_slot; */
+ fncontext fnctx = ctx->peek_fn ();
+ tree result_reference
+ = Backend::var_expression (fnctx.ret_addr, lvalue_locus);
+ tree assignment = Backend::assignment_statement (result_reference,
+ return_value, locus);
+ ctx->add_statement (assignment);
+
CompileDrop (ctx).emit_current_scope_drop_calls ();
+ result_reference = Backend::var_expression (fnctx.ret_addr, locus);
tree return_stmt
- = Backend::return_statement (fndecl, return_value, locus);
+ = Backend::return_statement (fndecl, result_reference, locus);
ctx->add_statement (return_stmt);
}
else
new file mode 100644
@@ -0,0 +1,46 @@
+// { dg-output "f\r*\nd\r*\n" }
+// { dg-additional-options "-w" }
+#![feature(no_core)]
+#![feature(lang_items)]
+#![no_core]
+
+extern "C" {
+ fn printf(s: *const i8, ...);
+}
+
+#[lang = "sized"]
+pub trait Sized {}
+
+#[lang = "drop"]
+pub trait Drop {
+ fn drop(&mut self);
+}
+
+struct Droppable;
+
+impl Drop for Droppable {
+ fn drop(&mut self) {
+ let msg = "d\n\0" as *const str as *const i8;
+ unsafe {
+ printf(msg);
+ }
+ }
+}
+
+fn foo() -> i32 {
+ let msg = "f\n\0" as *const str as *const i8;
+ unsafe {
+ printf(msg);
+ }
+
+ 0
+}
+
+fn f() -> i32 {
+ let _x = Droppable;
+ foo()
+}
+
+fn main() -> i32 {
+ f()
+}