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Avoid an unnecessary use of SmallStr.

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I don't know why `SmallStr` was used here; some ad hoc profiling showed
this code is not that hot, the string is usually empty, and when it's
not empty it's usually very short. However, the use of a
`SmallStr<1024>` does result in 1024 byte `memcpy` call on each
execution, which shows up when I do `memcpy` profiling. So using a
normal string makes the code both simpler and very slightly faster.
This commit is contained in:
Nicholas Nethercote 2023-06-28 11:30:27 +10:00
parent 45fcd1d0c5
commit de1914af34
1 changed files with 2 additions and 3 deletions
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5
compiler/rustc_codegen_llvm/src/attributes.rs
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@ -1,7 +1,6 @@
//! Set and unset common attributes on LLVM values. //! Set and unset common attributes on LLVM values.
use rustc_codegen_ssa::traits::*; use rustc_codegen_ssa::traits::*;
use rustc_data_structures::small_str::SmallStr;
use rustc_hir::def_id::DefId; use rustc_hir::def_id::DefId;
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags; use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use rustc_middle::ty::{self, TyCtxt}; use rustc_middle::ty::{self, TyCtxt};
@ -481,8 +480,8 @@ pub fn from_fn_attrs<'ll, 'tcx>(
let global_features = cx.tcx.global_backend_features(()).iter().map(|s| s.as_str()); let global_features = cx.tcx.global_backend_features(()).iter().map(|s| s.as_str());
let function_features = function_features.iter().map(|s| s.as_str()); let function_features = function_features.iter().map(|s| s.as_str());
let target_features = let target_features: String =
global_features.chain(function_features).intersperse(",").collect::<SmallStr<1024>>(); global_features.chain(function_features).intersperse(",").collect();
if !target_features.is_empty() { if !target_features.is_empty() {
to_add.push(llvm::CreateAttrStringValue(cx.llcx, "target-features", &target_features)); to_add.push(llvm::CreateAttrStringValue(cx.llcx, "target-features", &target_features));
} }