From 6db68938ac3cb510f196c2649cea397aba403c9c Mon Sep 17 00:00:00 2001
From: Eduard-Mihai Burtescu <edy.burt@gmail.com>
Date: Wed, 15 Nov 2017 03:35:35 +0200
Subject: [PATCH] MIR: hide .rodata constants vs by-ref ABI clash in trans.
---
src/librustc/mir/mod.rs | 7 ++++---
src/librustc_mir/build/expr/into.rs | 8 +-------
src/librustc_trans/mir/block.rs | 11 ++++++++++-
src/test/mir-opt/nll/liveness-call-subtlety.rs | 12 +++---------
.../nll/region-liveness-drop-no-may-dangle.rs | 2 +-
.../nll/region-liveness-two-disjoint-uses.rs | 2 +-
src/test/run-pass/mir_trans_calls.rs | 17 ++++++++++++++++-
7 files changed, 36 insertions(+), 23 deletions(-)
diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs
index bea273c84a92e..3cc159978a873 100644
--- a/src/librustc/mir/mod.rs
+++ b/src/librustc/mir/mod.rs
@@ -684,9 +684,10 @@ pub enum TerminatorKind<'tcx> {
Call {
/// The function that’s being called
func: Operand<'tcx>,
- /// Arguments the function is called with. These are owned by the callee, which is free to
- /// modify them. This is important as "by-value" arguments might be passed by-reference at
- /// the ABI level.
+ /// Arguments the function is called with.
+ /// These are owned by the callee, which is free to modify them.
+ /// This allows the memory occupied by "by-value" arguments to be
+ /// reused across function calls without duplicating the contents.
args: Vec<Operand<'tcx>>,
/// Destination for the return value. If some, the call is converging.
destination: Option<(Lvalue<'tcx>, BasicBlock)>,
diff --git a/src/librustc_mir/build/expr/into.rs b/src/librustc_mir/build/expr/into.rs
index 280e1c8196636..cdbcb43370fe0 100644
--- a/src/librustc_mir/build/expr/into.rs
+++ b/src/librustc_mir/build/expr/into.rs
@@ -247,13 +247,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
} else {
let args: Vec<_> =
args.into_iter()
- .map(|arg| {
- let scope = this.local_scope();
- // Function arguments are owned by the callee, so we need as_temp()
- // instead of as_operand() to enforce copies
- let operand = unpack!(block = this.as_temp(block, scope, arg));
- Operand::Consume(Lvalue::Local(operand))
- })
+ .map(|arg| unpack!(block = this.as_local_operand(block, arg)))
.collect();
let success = this.cfg.start_new_block();
diff --git a/src/librustc_trans/mir/block.rs b/src/librustc_trans/mir/block.rs
index 11d992bd4cf0e..bd26c961bb28b 100644
--- a/src/librustc_trans/mir/block.rs
+++ b/src/librustc_trans/mir/block.rs
@@ -524,7 +524,16 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
}
}
- let op = self.trans_operand(&bcx, arg);
+ let mut op = self.trans_operand(&bcx, arg);
+
+ // The callee needs to own the argument memory if we pass it
+ // by-ref, so make a local copy of non-immediate constants.
+ if let (&mir::Operand::Constant(_), Ref(..)) = (arg, op.val) {
+ let tmp = LvalueRef::alloca(&bcx, op.ty, "const");
+ self.store_operand(&bcx, tmp.llval, tmp.alignment.to_align(), op);
+ op.val = Ref(tmp.llval, tmp.alignment);
+ }
+
self.trans_argument(&bcx, op, &mut llargs, &fn_ty,
&mut idx, &mut llfn, &def);
}
diff --git a/src/test/mir-opt/nll/liveness-call-subtlety.rs b/src/test/mir-opt/nll/liveness-call-subtlety.rs
index 2de3e7d704d56..59a1d4891f66f 100644
--- a/src/test/mir-opt/nll/liveness-call-subtlety.rs
+++ b/src/test/mir-opt/nll/liveness-call-subtlety.rs
@@ -31,21 +31,15 @@ fn main() {
// | Live variables at bb0[0]: []
// StorageLive(_1);
// | Live variables at bb0[1]: []
-// StorageLive(_2);
-// | Live variables at bb0[2]: []
-// _2 = const 22usize;
-// | Live variables at bb0[3]: [_2]
-// _1 = const <std::boxed::Box<T>>::new(_2) -> bb1;
+// _1 = const <std::boxed::Box<T>>::new(const 22usize) -> bb1;
// }
// END rustc.main.nll.0.mir
// START rustc.main.nll.0.mir
// | Live variables on entry to bb1: [_1 (drop)]
// bb1: {
// | Live variables at bb1[0]: [_1 (drop)]
-// StorageDead(_2);
+// StorageLive(_2);
// | Live variables at bb1[1]: [_1 (drop)]
-// StorageLive(_3);
-// | Live variables at bb1[2]: [_1 (drop)]
-// _3 = const can_panic() -> [return: bb2, unwind: bb4];
+// _2 = const can_panic() -> [return: bb2, unwind: bb4];
// }
// END rustc.main.nll.0.mir
diff --git a/src/test/mir-opt/nll/region-liveness-drop-no-may-dangle.rs b/src/test/mir-opt/nll/region-liveness-drop-no-may-dangle.rs
index 2968ae7d485b1..aaeebe7495166 100644
--- a/src/test/mir-opt/nll/region-liveness-drop-no-may-dangle.rs
+++ b/src/test/mir-opt/nll/region-liveness-drop-no-may-dangle.rs
@@ -46,5 +46,5 @@ impl<T> Drop for Wrap<T> {
// END RUST SOURCE
// START rustc.main.nll.0.mir
-// | '_#5r: {bb1[3], bb1[4], bb1[5], bb2[0], bb2[1], bb2[2], bb3[0], bb3[1], bb3[2], bb4[0], bb4[1], bb4[2], bb6[0], bb7[0], bb7[1], bb7[2], bb8[0]}
+// | '_#5r: {bb1[3], bb1[4], bb1[5], bb2[0], bb2[1], bb2[2], bb3[0], bb4[0], bb4[1], bb4[2], bb6[0], bb7[0], bb7[1], bb8[0]}
// END rustc.main.nll.0.mir
diff --git a/src/test/mir-opt/nll/region-liveness-two-disjoint-uses.rs b/src/test/mir-opt/nll/region-liveness-two-disjoint-uses.rs
index 736d2902ec63f..5c28746126a64 100644
--- a/src/test/mir-opt/nll/region-liveness-two-disjoint-uses.rs
+++ b/src/test/mir-opt/nll/region-liveness-two-disjoint-uses.rs
@@ -45,5 +45,5 @@ fn main() {
// ...
// _2 = &'_#1r _1[_3];
// ...
-// _2 = &'_#3r (*_11);
+// _2 = &'_#3r (*_10);
// END rustc.main.nll.0.mir
diff --git a/src/test/run-pass/mir_trans_calls.rs b/src/test/run-pass/mir_trans_calls.rs
index d429c681bbe4a..d02e3287bc38a 100644
--- a/src/test/run-pass/mir_trans_calls.rs
+++ b/src/test/run-pass/mir_trans_calls.rs
@@ -8,7 +8,9 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
-#![feature(fn_traits)]
+#![feature(fn_traits, test)]
+
+extern crate test;
fn test1(a: isize, b: (i32, i32), c: &[i32]) -> (isize, (i32, i32), &[i32]) {
// Test passing a number of arguments including a fat pointer.
@@ -156,6 +158,16 @@ fn test_fn_nested_pair(x: &((f32, f32), u32)) -> (f32, f32) {
(z.0, z.1)
}
+fn test_fn_const_arg_by_ref(mut a: [u64; 4]) -> u64 {
+ // Mutate the by-reference argument, which won't work with
+ // a non-immediate constant unless it's copied to the stack.
+ let a = test::black_box(&mut a);
+ a[0] += a[1];
+ a[0] += a[2];
+ a[0] += a[3];
+ a[0]
+}
+
fn main() {
assert_eq!(test1(1, (2, 3), &[4, 5, 6]), (1, (2, 3), &[4, 5, 6][..]));
assert_eq!(test2(98), 98);
@@ -182,4 +194,7 @@ fn main() {
assert_eq!(test_fn_ignored_pair_0(), ());
assert_eq!(test_fn_ignored_pair_named(), (Foo, Foo));
assert_eq!(test_fn_nested_pair(&((1.0, 2.0), 0)), (1.0, 2.0));
+
+ const ARRAY: [u64; 4] = [1, 2, 3, 4];
+ assert_eq!(test_fn_const_arg_by_ref(ARRAY), 1 + 2 + 3 + 4);
}