From 631cd5845e8de329d0e227aaa707d7ea228b8f8f Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:20:29 +0200 Subject: Merging upstream version 1.70.0+dfsg1. Signed-off-by: Daniel Baumann --- .../issues/issue-96497-slice-size-nowrap.rs | 29 ++++++++++++++++++++++ 1 file changed, 29 insertions(+) create mode 100644 tests/codegen/issues/issue-96497-slice-size-nowrap.rs (limited to 'tests/codegen/issues/issue-96497-slice-size-nowrap.rs') diff --git a/tests/codegen/issues/issue-96497-slice-size-nowrap.rs b/tests/codegen/issues/issue-96497-slice-size-nowrap.rs new file mode 100644 index 000000000..0413ed6b2 --- /dev/null +++ b/tests/codegen/issues/issue-96497-slice-size-nowrap.rs @@ -0,0 +1,29 @@ +// This test case checks that LLVM is aware that computing the size of a slice cannot wrap. +// The possibility of wrapping results in an additional branch when dropping boxed slices +// in some situations, see https://github.com/rust-lang/rust/issues/96497#issuecomment-1112865218 + +// compile-flags: -O +// min-llvm-version: 15.0 + +#![crate_type="lib"] + +// CHECK-LABEL: @simple_size_of_nowrap +#[no_mangle] +pub fn simple_size_of_nowrap(x: &[u32]) -> usize { + // Make sure the shift used to compute the size has a nowrap flag. + + // CHECK: [[A:%.*]] = shl nsw {{.*}}, 2 + // CHECK-NEXT: ret {{.*}} [[A]] + core::mem::size_of_val(x) +} + +// CHECK-LABEL: @drop_write +#[no_mangle] +pub fn drop_write(mut x: Box<[u32]>) { + // Check that this write is optimized out. + // This depends on the size calculation not wrapping, + // since otherwise LLVM can't tell that the memory is always deallocated if the slice len > 0. + + // CHECK-NOT: store i32 42 + x[1] = 42; +} -- cgit v1.2.3