bjoernager/rust
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Auto merge of #137271 - nikic:gep-nuw-2, r=scottmcm

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Emit getelementptr inbounds nuw for pointer::add()

Lower pointer::add (via intrinsic::offset with unsigned offset) to getelementptr inbounds nuw on LLVM versions that support it. This lets LLVM make use of the pre-condition that the offset addition does not wrap in an unsigned sense. Together with inbounds, this also implies that the offset is non-negative.

Fixes https://github.com/rust-lang/rust/issues/137217.
This commit is contained in:
bors 2025-02-24 03:06:16 +00:00
commit e0be1a0262
10 changed files with 93 additions and 29 deletions
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2
compiler/rustc_codegen_ssa/src/mir/place.rs
View file

@ -423,7 +423,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
layout.size
};
let llval = bx.inbounds_gep(bx.cx().backend_type(layout), self.val.llval, &[llindex]);
let llval = bx.inbounds_nuw_gep(bx.cx().backend_type(layout), self.val.llval, &[llindex]);
let align = self.val.align.restrict_for_offset(offset);
PlaceValue::new_sized(llval, align).with_type(layout)
}

29
compiler/rustc_codegen_ssa/src/mir/rvalue.rs
View file

@ -666,9 +666,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
lhs.layout.ty,
),
(OperandValue::Immediate(lhs_val), OperandValue::Immediate(rhs_val)) => {
self.codegen_scalar_binop(bx, op, lhs_val, rhs_val, lhs.layout.ty)
}
(OperandValue::Immediate(lhs_val), OperandValue::Immediate(rhs_val)) => self
.codegen_scalar_binop(
bx,
op,
lhs_val,
rhs_val,
lhs.layout.ty,
rhs.layout.ty,
),
_ => bug!(),
};
@ -889,10 +895,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
op: mir::BinOp,
lhs: Bx::Value,
rhs: Bx::Value,
input_ty: Ty<'tcx>,
lhs_ty: Ty<'tcx>,
rhs_ty: Ty<'tcx>,
) -> Bx::Value {
let is_float = input_ty.is_floating_point();
let is_signed = input_ty.is_signed();
let is_float = lhs_ty.is_floating_point();
let is_signed = lhs_ty.is_signed();
match op {
mir::BinOp::Add => {
if is_float {
@ -958,9 +965,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
mir::BinOp::BitAnd => bx.and(lhs, rhs),
mir::BinOp::BitXor => bx.xor(lhs, rhs),
mir::BinOp::Offset => {
let pointee_type = input_ty
let pointee_type = lhs_ty
.builtin_deref(true)
.unwrap_or_else(|| bug!("deref of non-pointer {:?}", input_ty));
.unwrap_or_else(|| bug!("deref of non-pointer {:?}", lhs_ty));
let pointee_layout = bx.cx().layout_of(pointee_type);
if pointee_layout.is_zst() {
// `Offset` works in terms of the size of pointee,
@ -968,7 +975,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
lhs
} else {
let llty = bx.cx().backend_type(pointee_layout);
bx.inbounds_gep(llty, lhs, &[rhs])
if !rhs_ty.is_signed() {
bx.inbounds_nuw_gep(llty, lhs, &[rhs])
} else {
bx.inbounds_gep(llty, lhs, &[rhs])
}
}
}
mir::BinOp::Shl | mir::BinOp::ShlUnchecked => {

8
compiler/rustc_codegen_ssa/src/traits/builder.rs
View file

@ -325,6 +325,14 @@ pub trait BuilderMethods<'a, 'tcx>:
ptr: Self::Value,
indices: &[Self::Value],
) -> Self::Value;
fn inbounds_nuw_gep(
&mut self,
ty: Self::Type,
ptr: Self::Value,
indices: &[Self::Value],
) -> Self::Value {
self.inbounds_gep(ty, ptr, indices)
}
fn ptradd(&mut self, ptr: Self::Value, offset: Self::Value) -> Self::Value {
self.gep(self.cx().type_i8(), ptr, &[offset])
}