From 130a1df71ea73ab9d66d3cb8fc9cdb43155d514b Mon Sep 17 00:00:00 2001 From: Augie Fackler Date: Mon, 21 Mar 2022 15:30:54 -0400 Subject: codegen: use new {re,de,}allocator annotations in llvm This obviates the patch that teaches LLVM internals about _rust_{re,de}alloc functions by putting annotations directly in the IR for the optimizer. The sole test change is required to anchor FileCheck to the body of the `box_uninitialized` method, so it doesn't see the `allocalign` on `__rust_alloc` and get mad about the string `alloca` showing up. Since I was there anyway, I added some checks on the attributes to prove the right attributes got set. While we're here, we also emit allocator attributes on __rust_alloc_zeroed. This should allow LLVM to perform more optimizations for zeroed blocks, and probably fixes #90032. [This comment](https://github.com/rust-lang/rust/issues/24194#issuecomment-308791157) mentions "weird UB-like behaviour with bitvec iterators in rustc_data_structures" so we may need to back this change out if things go wrong. The new test cases require LLVM 15, so we copy them into LLVM 14-supporting versions, which we can delete when we drop LLVM 14. --- compiler/rustc_middle/src/middle/codegen_fn_attrs.rs | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'compiler/rustc_middle') diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs index 321fcd43797..45d33a1659f 100644 --- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs +++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs @@ -50,7 +50,7 @@ bitflags! { /// the hot path. const COLD = 1 << 0; /// `#[rustc_allocator]`: a hint to LLVM that the pointer returned from this - /// function is never null. + /// function is never null and the function has no side effects other than allocating. const ALLOCATOR = 1 << 1; /// An indicator that function will never unwind. Will become obsolete /// once C-unwind is fully stabilized. @@ -91,6 +91,12 @@ bitflags! { const NO_COVERAGE = 1 << 15; /// `#[used(linker)]`: indicates that LLVM nor the linker can eliminate this function. const USED_LINKER = 1 << 16; + /// `#[rustc_deallocator]`: a hint to LLVM that the function only deallocates memory. + const DEALLOCATOR = 1 << 17; + /// `#[rustc_reallocator]`: a hint to LLVM that the function only reallocates memory. + const REALLOCATOR = 1 << 18; + /// `#[rustc_allocator_zeroed]`: a hint to LLVM that the function only allocates zeroed memory. + const ALLOCATOR_ZEROED = 1 << 19; } } -- cgit 1.4.1-3-g733a5