factor SIMD bool handling into helper functions

Author: RalfJung

src/helpers.rs

@@ -758,3 +758,18 @@ pub fn immty_from_uint_checked<'tcx>(
         err_unsup_format!("unsigned value {:#x} does not fit in {} bits", int, layout.size.bits())
     })?)
 }
+
+pub fn bool_to_simd_element(b: bool, size: Size) -> Scalar<Tag> {
+    // SIMD uses all-1 as pattern for "true"
+    let val = if b { -1 } else { 0 };
+    Scalar::from_int(val, size)
+}
+
+pub fn simd_element_to_bool<'tcx>(elem: ImmTy<'tcx, Tag>) -> InterpResult<'tcx, bool> {
+    let val = elem.to_scalar()?.to_int(elem.layout.size)?;
+    Ok(match val {
+        0 => false,
+        -1 => true,
+        _ => throw_ub_format!("each element of a SIMD mask must be all-0-bits or all-1-bits"),
+    })
+}

src/shims/intrinsics.rs

@@ -8,7 +8,7 @@ use rustc_middle::{mir, mir::BinOp, ty, ty::FloatTy};
 use rustc_target::abi::{Align, Integer};
 
 use crate::*;
-use helpers::check_arg_count;
+use helpers::{bool_to_simd_element, check_arg_count, simd_element_to_bool};
 
 pub enum AtomicOp {
     MirOp(mir::BinOp, bool),
@@ -365,8 +365,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                         // Special handling for boolean-returning operations
                         assert_eq!(ty, this.tcx.types.bool);
                         let val = val.to_bool().unwrap();
-                        let val = if val { -1 } else { 0 }; // SIMD uses all-1 as pattern for "true"
-                        let val = Scalar::from_int(val, dest.layout.size);
+                        let val = bool_to_simd_element(val, dest.layout.size);
                         this.write_scalar(val, &dest.into())?;
                     } else {
                         assert_eq!(ty, dest.layout.ty);
@@ -381,16 +380,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let mut res = false; // the neutral element
                 for i in 0..arg_len {
                     let op = this.read_immediate(&this.mplace_index(&arg, i)?.into())?;
-                    // We convert it to a *signed* integer and expect either 0 or -1 (the latter means all bits were set).
-                    let val = op.to_scalar()?.to_int(op.layout.size)?;
-                    let val = match val {
-                        0 => false,
-                        -1 => true,
-                        _ =>
-                            throw_ub_format!(
-                                "each element of a simd_reduce_any operand must be all-0-bits or all-1-bits"
-                            ),
-                    };
+                    let val = simd_element_to_bool(op)?;
                     res = res | val;
                 }