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| author | Xiang Fan <sfanxiang@gmail.com> | 2019-06-06 08:39:20 +0800 |
|---|---|---|
| committer | Xiang Fan <sfanxiang@gmail.com> | 2019-09-28 04:45:08 +0800 |
| commit | f71e0daa29b232d8f689f77fecb84dcb87fce6da (patch) | |
| tree | 7e450a5f114b0973aad2b5b7799bc7f54c6776c7 /src/test/codegen/alloc-optimisation.rs | |
| parent | a37fe2de697bb1a9d304e4e811836e125f944cd5 (diff) | |
| download | rust-f71e0daa29b232d8f689f77fecb84dcb87fce6da.tar.gz rust-f71e0daa29b232d8f689f77fecb84dcb87fce6da.zip | |
Add llvm.sideeffect to potential infinite loops and recursions
LLVM assumes that a thread will eventually cause side effect. This is
not true in Rust if a loop or recursion does nothing in its body,
causing undefined behavior even in common cases like `loop {}`.
Inserting llvm.sideeffect fixes the undefined behavior.
As a micro-optimization, only insert llvm.sideeffect when jumping back
in blocks or calling a function.
A patch for LLVM is expected to allow empty non-terminate code by
default and fix this issue from LLVM side.
https://github.com/rust-lang/rust/issues/28728
Diffstat (limited to 'src/test/codegen/alloc-optimisation.rs')
| -rw-r--r-- | src/test/codegen/alloc-optimisation.rs | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/test/codegen/alloc-optimisation.rs b/src/test/codegen/alloc-optimisation.rs index c3ffaeb9547..c1e36a17ec2 100644 --- a/src/test/codegen/alloc-optimisation.rs +++ b/src/test/codegen/alloc-optimisation.rs @@ -7,7 +7,8 @@ pub fn alloc_test(data: u32) { // CHECK-LABEL: @alloc_test // CHECK-NEXT: start: - // CHECK-NEXT: ret void + // CHECK-NOT: alloc + // CHECK: ret void let x = Box::new(data); drop(x); } |