From 4f78f9fbb05145d437540181fda9bcc83d5a53e4 Mon Sep 17 00:00:00 2001 From: Amanieu d'Antras Date: Fri, 26 Jul 2024 19:36:21 +0100 Subject: Force LLVM to use CMOV for binary search Since https://reviews.llvm.org/D118118, LLVM will no longer turn CMOVs into branches if it comes from a `select` marked with an `unpredictable` metadata attribute. This PR introduces `core::intrinsics::select_unpredictable` which emits such a `select` and uses it in the implementation of `binary_search_by`. --- tests/codegen/intrinsics/select_unpredictable.rs | 35 ++++++++++++++++++++++++ 1 file changed, 35 insertions(+) create mode 100644 tests/codegen/intrinsics/select_unpredictable.rs (limited to 'tests/codegen') diff --git a/tests/codegen/intrinsics/select_unpredictable.rs b/tests/codegen/intrinsics/select_unpredictable.rs new file mode 100644 index 00000000000..2054838dd79 --- /dev/null +++ b/tests/codegen/intrinsics/select_unpredictable.rs @@ -0,0 +1,35 @@ +//@ compile-flags: -O + +#![feature(core_intrinsics)] +#![crate_type = "lib"] + +#[no_mangle] +pub fn test_int(p: bool, a: u64, b: u64) -> u64 { + // CHECK-LABEL: define{{.*}} @test_int + // CHECK: select i1 %p, i64 %a, i64 %b, !unpredictable + core::intrinsics::select_unpredictable(p, a, b) +} + +#[no_mangle] +pub fn test_pair(p: bool, a: (u64, u64), b: (u64, u64)) -> (u64, u64) { + // CHECK-LABEL: define{{.*}} @test_pair + // CHECK: select i1 %p, {{.*}}, !unpredictable + core::intrinsics::select_unpredictable(p, a, b) +} + +struct Large { + e: [u64; 100], +} + +#[no_mangle] +pub fn test_struct(p: bool, a: Large, b: Large) -> Large { + // CHECK-LABEL: define{{.*}} @test_struct + // CHECK: select i1 %p, {{.*}}, !unpredictable + core::intrinsics::select_unpredictable(p, a, b) +} + +#[no_mangle] +pub fn test_zst(p: bool, a: (), b: ()) -> () { + // CHECK-LABEL: define{{.*}} @test_zst + core::intrinsics::select_unpredictable(p, a, b) +} -- cgit 1.4.1-3-g733a5