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Auto merge of #121614 - clubby789:no-expect, r=saethlin

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Don't emit `expect`/`assume` in opt-level=0

LLVM does not make use of expect/assume calls in `opt-level=0`, so we can simplify IR by not emitting them in this case.
This commit is contained in:
bors 2024-09-06 00:42:58 +00:00
commit 54fdef7799
4 changed files with 14 additions and 14 deletions
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17
compiler/rustc_codegen_llvm/src/intrinsic.rs
View File

@ -187,9 +187,7 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
Some(instance),
)
}
sym::likely => {
self.call_intrinsic("llvm.expect.i1", &[args[0].immediate(), self.const_bool(true)])
}
sym::likely => self.expect(args[0].immediate(), true),
sym::is_val_statically_known => {
let intrinsic_type = args[0].layout.immediate_llvm_type(self.cx);
let kind = self.type_kind(intrinsic_type);
@ -210,8 +208,7 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
self.const_bool(false)
}
}
sym::unlikely => self
.call_intrinsic("llvm.expect.i1", &[args[0].immediate(), self.const_bool(false)]),
sym::unlikely => self.expect(args[0].immediate(), false),
sym::select_unpredictable => {
let cond = args[0].immediate();
assert_eq!(args[1].layout, args[2].layout);
@ -604,11 +601,17 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
}
fn assume(&mut self, val: Self::Value) {
self.call_intrinsic("llvm.assume", &[val]);
if self.cx.sess().opts.optimize != rustc_session::config::OptLevel::No {
self.call_intrinsic("llvm.assume", &[val]);
}
}
fn expect(&mut self, cond: Self::Value, expected: bool) -> Self::Value {
self.call_intrinsic("llvm.expect.i1", &[cond, self.const_bool(expected)])
if self.cx.sess().opts.optimize != rustc_session::config::OptLevel::No {
self.call_intrinsic("llvm.expect.i1", &[cond, self.const_bool(expected)])
} else {
cond
}
}
fn type_test(&mut self, pointer: Self::Value, typeid: Self::Value) -> Self::Value {

2
compiler/rustc_codegen_ssa/src/mir/rvalue.rs
View File

@ -382,7 +382,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
scalar: abi::Scalar,
backend_ty: Bx::Type,
) {
if matches!(self.cx.sess().opts.optimize, OptLevel::No | OptLevel::Less)
if matches!(self.cx.sess().opts.optimize, OptLevel::No)
// For now, the critical niches are all over `Int`eger values.
// Should floating-point values or pointers ever get more complex
// niches, then this code will probably want to handle them too.

7
compiler/rustc_codegen_ssa/src/mir/statement.rs
View File

@ -1,6 +1,5 @@
use rustc_middle::mir::{self, NonDivergingIntrinsic};
use rustc_middle::span_bug;
use rustc_session::config::OptLevel;
use tracing::instrument;
use super::{FunctionCx, LocalRef};
@ -68,10 +67,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
self.codegen_coverage(bx, kind, statement.source_info.scope);
}
mir::StatementKind::Intrinsic(box NonDivergingIntrinsic::Assume(ref op)) => {
if !matches!(bx.tcx().sess.opts.optimize, OptLevel::No | OptLevel::Less) {
let op_val = self.codegen_operand(bx, op);
bx.assume(op_val.immediate());
}
let op_val = self.codegen_operand(bx, op);
bx.assume(op_val.immediate());
}
mir::StatementKind::Intrinsic(box NonDivergingIntrinsic::CopyNonOverlapping(
mir::CopyNonOverlapping { ref count, ref src, ref dst },

2
tests/codegen/intrinsics/likely.rs
View File

@ -1,4 +1,4 @@
//@ compile-flags: -C no-prepopulate-passes
//@ compile-flags: -C no-prepopulate-passes -Copt-level=1
#![crate_type = "lib"]
#![feature(core_intrinsics)]