From 511bf307f03d7045f54a376d389ebdf9786e7a24 Mon Sep 17 00:00:00 2001 From: Scott McMurray Date: Fri, 14 Feb 2025 20:25:43 -0800 Subject: Emit `trunc nuw` for unchecked shifts and `to_immediate_scalar` MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit - For shifts this shrinks the IR by no longer needing an `assume` while still providing the UB information - Having this on the `i8`→`i1` truncations will hopefully help with some places that have to load `i8`s or pass those in LLVM structs without range information --- compiler/rustc_codegen_ssa/src/base.rs | 10 ++-------- compiler/rustc_codegen_ssa/src/traits/builder.rs | 11 +++++++++++ 2 files changed, 13 insertions(+), 8 deletions(-) (limited to 'compiler/rustc_codegen_ssa/src') diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs index e800492dad0..a989e9c64c0 100644 --- a/compiler/rustc_codegen_ssa/src/base.rs +++ b/compiler/rustc_codegen_ssa/src/base.rs @@ -24,7 +24,7 @@ use rustc_middle::query::Providers; use rustc_middle::ty::layout::{HasTyCtxt, HasTypingEnv, LayoutOf, TyAndLayout}; use rustc_middle::ty::{self, Instance, Ty, TyCtxt}; use rustc_session::Session; -use rustc_session::config::{self, CrateType, EntryFnType, OptLevel, OutputType}; +use rustc_session::config::{self, CrateType, EntryFnType, OutputType}; use rustc_span::{DUMMY_SP, Symbol, sym}; use rustc_trait_selection::infer::{BoundRegionConversionTime, TyCtxtInferExt}; use rustc_trait_selection::traits::{ObligationCause, ObligationCtxt}; @@ -364,13 +364,7 @@ pub(crate) fn build_shift_expr_rhs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( let rhs_sz = bx.cx().int_width(rhs_llty); let lhs_sz = bx.cx().int_width(lhs_llty); if lhs_sz < rhs_sz { - if is_unchecked && bx.sess().opts.optimize != OptLevel::No { - // FIXME: Use `trunc nuw` once that's available - let inrange = bx.icmp(IntPredicate::IntULE, rhs, mask); - bx.assume(inrange); - } - - bx.trunc(rhs, lhs_llty) + if is_unchecked { bx.unchecked_utrunc(rhs, lhs_llty) } else { bx.trunc(rhs, lhs_llty) } } else if lhs_sz > rhs_sz { // We zero-extend even if the RHS is signed. So e.g. `(x: i32) << -1i8` will zero-extend the // RHS to `255i32`. But then we mask the shift amount to be within the size of the LHS diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs index 48ae000f2c6..345db313022 100644 --- a/compiler/rustc_codegen_ssa/src/traits/builder.rs +++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs @@ -340,6 +340,17 @@ pub trait BuilderMethods<'a, 'tcx>: } fn trunc(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value; + /// Produces the same value as [`Self::trunc`] (and defaults to that), + /// but is UB unless the *zero*-extending the result can reproduce `val`. + fn unchecked_utrunc(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value { + self.trunc(val, dest_ty) + } + /// Produces the same value as [`Self::trunc`] (and defaults to that), + /// but is UB unless the *sign*-extending the result can reproduce `val`. + fn unchecked_strunc(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value { + self.trunc(val, dest_ty) + } + fn sext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value; fn fptoui_sat(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value; fn fptosi_sat(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value; -- cgit 1.4.1-3-g733a5