Stop generating assumes for validity ranges

Now that LLVM has implemented range attributes on arguments and returns,
and now that we generate such attributes, we no longer need to use
assumes to represent validity ranges.

Author: erikdesjardins

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -240,13 +240,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 if let OperandValueKind::Immediate(to_scalar) = cast_kind
                     && from_scalar.size(self.cx) == to_scalar.size(self.cx)
                 {
-                    let from_backend_ty = bx.backend_type(operand.layout);
                     let to_backend_ty = bx.backend_type(cast);
                     Some(OperandValue::Immediate(self.transmute_immediate(
                         bx,
                         imm,
                         from_scalar,
-                        from_backend_ty,
                         to_scalar,
                         to_backend_ty,
                     )))
@@ -262,13 +260,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     && in_a.size(self.cx) == out_a.size(self.cx)
                     && in_b.size(self.cx) == out_b.size(self.cx)
                 {
-                    let in_a_ibty = bx.scalar_pair_element_backend_type(operand.layout, 0, false);
-                    let in_b_ibty = bx.scalar_pair_element_backend_type(operand.layout, 1, false);
                     let out_a_ibty = bx.scalar_pair_element_backend_type(cast, 0, false);
                     let out_b_ibty = bx.scalar_pair_element_backend_type(cast, 1, false);
                     Some(OperandValue::Pair(
-                        self.transmute_immediate(bx, imm_a, in_a, in_a_ibty, out_a, out_a_ibty),
-                        self.transmute_immediate(bx, imm_b, in_b, in_b_ibty, out_b, out_b_ibty),
+                        self.transmute_immediate(bx, imm_a, in_a, out_a, out_a_ibty),
+                        self.transmute_immediate(bx, imm_b, in_b, out_b, out_b_ibty),
                     ))
                 } else {
                     None
@@ -292,12 +288,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     ) -> Option<Bx::Value> {
         use abi::Primitive::*;
 
-        // When scalars are passed by value, there's no metadata recording their
-        // valid ranges. For example, `char`s are passed as just `i32`, with no
-        // way for LLVM to know that they're 0x10FFFF at most. Thus we assume
-        // the range of the input value too, not just the output range.
-        self.assume_scalar_range(bx, imm, from_scalar, from_backend_ty);
-
         imm = match (from_scalar.primitive(), to_scalar.primitive()) {
             (Int(_, is_signed), Int(..)) => bx.intcast(imm, to_backend_ty, is_signed),
             (Float(_), Float(_)) => {
@@ -339,21 +329,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         bx: &mut Bx,
         mut imm: Bx::Value,
         from_scalar: abi::Scalar,
-        from_backend_ty: Bx::Type,
         to_scalar: abi::Scalar,
         to_backend_ty: Bx::Type,
     ) -> Bx::Value {
+        use abi::Primitive::*;
+
         assert_eq!(from_scalar.size(self.cx), to_scalar.size(self.cx));
 
-        use abi::Primitive::*;
         imm = bx.from_immediate(imm);
 
-        // When scalars are passed by value, there's no metadata recording their
-        // valid ranges. For example, `char`s are passed as just `i32`, with no
-        // way for LLVM to know that they're 0x10FFFF at most. Thus we assume
-        // the range of the input value too, not just the output range.
-        self.assume_scalar_range(bx, imm, from_scalar, from_backend_ty);
-
         imm = match (from_scalar.primitive(), to_scalar.primitive()) {
             (Int(..) | Float(_), Int(..) | Float(_)) => bx.bitcast(imm, to_backend_ty),
             (Pointer(..), Pointer(..)) => bx.pointercast(imm, to_backend_ty),
@@ -368,55 +352,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 bx.bitcast(int_imm, to_backend_ty)
             }
         };
-        self.assume_scalar_range(bx, imm, to_scalar, to_backend_ty);
         imm = bx.to_immediate_scalar(imm, to_scalar);
         imm
     }
 
-    fn assume_scalar_range(
-        &self,
-        bx: &mut Bx,
-        imm: Bx::Value,
-        scalar: abi::Scalar,
-        backend_ty: Bx::Type,
-    ) {
-        if matches!(self.cx.sess().opts.optimize, OptLevel::No | OptLevel::Less)
-            // 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.
-            || !matches!(scalar.primitive(), abi::Primitive::Int(..))
-            || scalar.is_always_valid(self.cx)
-        {
-            return;
-        }
-
-        let abi::WrappingRange { start, end } = scalar.valid_range(self.cx);
-
-        if start <= end {
-            if start > 0 {
-                let low = bx.const_uint_big(backend_ty, start);
-                let cmp = bx.icmp(IntPredicate::IntUGE, imm, low);
-                bx.assume(cmp);
-            }
-
-            let type_max = scalar.size(self.cx).unsigned_int_max();
-            if end < type_max {
-                let high = bx.const_uint_big(backend_ty, end);
-                let cmp = bx.icmp(IntPredicate::IntULE, imm, high);
-                bx.assume(cmp);
-            }
-        } else {
-            let low = bx.const_uint_big(backend_ty, start);
-            let cmp_low = bx.icmp(IntPredicate::IntUGE, imm, low);
-
-            let high = bx.const_uint_big(backend_ty, end);
-            let cmp_high = bx.icmp(IntPredicate::IntULE, imm, high);
-
-            let or = bx.or(cmp_low, cmp_high);
-            bx.assume(or);
-        }
-    }
-
     pub fn codegen_rvalue_unsized(
         &mut self,
         bx: &mut Bx,

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -8,12 +8,11 @@ use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use rustc_middle::ty::cast::{mir_cast_kind, CastTy};
-use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::ty::util::IntTypeExt;
 use rustc_middle::ty::{self, Ty, UpvarArgs};
 use rustc_span::source_map::Spanned;
 use rustc_span::{Span, DUMMY_SP};
-use rustc_target::abi::{Abi, FieldIdx, Primitive};
+use rustc_target::abi::FieldIdx;
 use tracing::debug;
 
 use crate::build::expr::as_place::PlaceBase;
@@ -201,85 +200,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 {
                     let discr_ty = adt_def.repr().discr_type().to_ty(this.tcx);
                     let temp = unpack!(block = this.as_temp(block, scope, source, Mutability::Not));
-                    let layout = this.tcx.layout_of(this.param_env.and(source_expr.ty));
                     let discr = this.temp(discr_ty, source_expr.span);
                     this.cfg.push_assign(
                         block,
                         source_info,
                         discr,
                         Rvalue::Discriminant(temp.into()),
                     );
-                    let (op, ty) = (Operand::Move(discr), discr_ty);
-
-                    if let Abi::Scalar(scalar) = layout.unwrap().abi
-                        && !scalar.is_always_valid(&this.tcx)
-                        && let Primitive::Int(int_width, _signed) = scalar.primitive()
-                    {
-                        let unsigned_ty = int_width.to_ty(this.tcx, false);
-                        let unsigned_place = this.temp(unsigned_ty, expr_span);
-                        this.cfg.push_assign(
-                            block,
-                            source_info,
-                            unsigned_place,
-                            Rvalue::Cast(CastKind::IntToInt, Operand::Copy(discr), unsigned_ty),
-                        );
-
-                        let bool_ty = this.tcx.types.bool;
-                        let range = scalar.valid_range(&this.tcx);
-                        let merge_op =
-                            if range.start <= range.end { BinOp::BitAnd } else { BinOp::BitOr };
-
-                        let mut comparer = |range: u128, bin_op: BinOp| -> Place<'tcx> {
-                            let range_val = Const::from_bits(
-                                this.tcx,
-                                range,
-                                ty::ParamEnv::empty().and(unsigned_ty),
-                            );
-                            let lit_op = this.literal_operand(expr.span, range_val);
-                            let is_bin_op = this.temp(bool_ty, expr_span);
-                            this.cfg.push_assign(
-                                block,
-                                source_info,
-                                is_bin_op,
-                                Rvalue::BinaryOp(
-                                    bin_op,
-                                    Box::new((Operand::Copy(unsigned_place), lit_op)),
-                                ),
-                            );
-                            is_bin_op
-                        };
-                        let assert_place = if range.start == 0 {
-                            comparer(range.end, BinOp::Le)
-                        } else {
-                            let start_place = comparer(range.start, BinOp::Ge);
-                            let end_place = comparer(range.end, BinOp::Le);
-                            let merge_place = this.temp(bool_ty, expr_span);
-                            this.cfg.push_assign(
-                                block,
-                                source_info,
-                                merge_place,
-                                Rvalue::BinaryOp(
-                                    merge_op,
-                                    Box::new((
-                                        Operand::Move(start_place),
-                                        Operand::Move(end_place),
-                                    )),
-                                ),
-                            );
-                            merge_place
-                        };
-                        this.cfg.push(
-                            block,
-                            Statement {
-                                source_info,
-                                kind: StatementKind::Intrinsic(Box::new(
-                                    NonDivergingIntrinsic::Assume(Operand::Move(assert_place)),
-                                )),
-                            },
-                        );
-                    }
-
-                    (op, ty)
+                    (Operand::Move(discr), discr_ty)
                 } else {
                     let ty = source_expr.ty;
                     let source = unpack!(

src/tools/tidy/src/issues.txt

@@ -3628,7 +3628,6 @@ ui/regions/issue-56537-closure-uses-region-from-container.rs
 ui/regions/issue-6157.rs
 ui/regions/issue-72051-member-region-hang.rs
 ui/regions/issue-78262.rs
-ui/repr/issue-83505-repr-simd.rs
 ui/resolve/auxiliary/issue-112831-aux.rs
 ui/resolve/auxiliary/issue-19452-aux.rs
 ui/resolve/auxiliary/issue-21221-3.rs

tests/codegen/cast-optimized.rs

@@ -1,4 +1,5 @@
 //@ compile-flags: -O -Z merge-functions=disabled
+//@ min-llvm-version: 19
 #![crate_type = "lib"]
 
 // This tests that LLVM can optimize based on the niches in the source or

tests/codegen/enum/enum-bounds-check-derived-idx.rs

@@ -1,6 +1,7 @@
 // This test checks an optimization that is not guaranteed to work. This test case should not block
 // a future LLVM update.
 //@ compile-flags: -O
+//@ min-llvm-version: 19
 
 #![crate_type = "lib"]
 

tests/codegen/enum/enum-bounds-check-issue-13926.rs

@@ -1,6 +1,7 @@
 // This test checks an optimization that is not guaranteed to work. This test case should not block
 // a future LLVM update.
 //@ compile-flags: -O
+//@ min-llvm-version: 19
 
 #![crate_type = "lib"]