Rollup merge of #105583 - luqmana:bitcast-immediates, r=oli-obk

Operand::extract_field: only cast llval if it's a pointer and replace bitcast w/ pointercast.

Fixes #105439.

Also cc `@erikdesjardins,` looks like another place to cleanup as part of #105545

compiler/rustc_codegen_ssa/src/mir/operand.rs

@@ -2,6 +2,7 @@ use super::place::PlaceRef;
 use super::{FunctionCx, LocalRef};
 
 use crate::base;
+use crate::common::TypeKind;
 use crate::glue;
 use crate::traits::*;
 use crate::MemFlags;
@@ -236,19 +237,47 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
         };
 
         match (&mut val, field.abi) {
-            (OperandValue::Immediate(llval), _) => {
+            (
+                OperandValue::Immediate(llval),
+                Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. },
+            ) => {
                 // Bools in union fields needs to be truncated.
                 *llval = bx.to_immediate(*llval, field);
                 // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
-                *llval = bx.bitcast(*llval, bx.cx().immediate_backend_type(field));
+                let ty = bx.cx().immediate_backend_type(field);
+                if bx.type_kind(ty) == TypeKind::Pointer {
+                    *llval = bx.pointercast(*llval, ty);
+                }
             }
             (OperandValue::Pair(a, b), Abi::ScalarPair(a_abi, b_abi)) => {
                 // Bools in union fields needs to be truncated.
                 *a = bx.to_immediate_scalar(*a, a_abi);
                 *b = bx.to_immediate_scalar(*b, b_abi);
                 // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
-                *a = bx.bitcast(*a, bx.cx().scalar_pair_element_backend_type(field, 0, true));
-                *b = bx.bitcast(*b, bx.cx().scalar_pair_element_backend_type(field, 1, true));
+                let a_ty = bx.cx().scalar_pair_element_backend_type(field, 0, true);
+                let b_ty = bx.cx().scalar_pair_element_backend_type(field, 1, true);
+                if bx.type_kind(a_ty) == TypeKind::Pointer {
+                    *a = bx.pointercast(*a, a_ty);
+                }
+                if bx.type_kind(b_ty) == TypeKind::Pointer {
+                    *b = bx.pointercast(*b, b_ty);
+                }
+            }
+            // Newtype vector of array, e.g. #[repr(simd)] struct S([i32; 4]);
+            (OperandValue::Immediate(llval), Abi::Aggregate { sized: true }) => {
+                assert!(matches!(self.layout.abi, Abi::Vector { .. }));
+
+                let llty = bx.cx().backend_type(self.layout);
+                let llfield_ty = bx.cx().backend_type(field);
+
+                // Can't bitcast an aggregate, so round trip through memory.
+                let lltemp = bx.alloca(llfield_ty, field.align.abi);
+                let llptr = bx.pointercast(lltemp, bx.cx().type_ptr_to(llty));
+                bx.store(*llval, llptr, field.align.abi);
+                *llval = bx.load(llfield_ty, lltemp, field.align.abi);
+            }
+            (OperandValue::Immediate(_), Abi::Uninhabited | Abi::Aggregate { sized: false }) => {
+                bug!()
             }
             (OperandValue::Pair(..), _) => bug!(),
             (OperandValue::Ref(..), _) => bug!(),

tests/ui/simd/issue-105439.rs

@@ -0,0 +1,25 @@
+// run-pass
+// compile-flags: -O -Zverify-llvm-ir
+
+#![feature(repr_simd)]
+#![feature(platform_intrinsics)]
+
+#[allow(non_camel_case_types)]
+#[derive(Clone, Copy)]
+#[repr(simd)]
+struct i32x4([i32; 4]);
+
+extern "platform-intrinsic" {
+    pub(crate) fn simd_add<T>(x: T, y: T) -> T;
+}
+
+#[inline(always)]
+fn to_array(a: i32x4) -> [i32; 4] {
+    a.0
+}
+
+fn main() {
+    let a = i32x4([1, 2, 3, 4]);
+    let b = unsafe { simd_add(a, a) };
+    assert_eq!(to_array(b), [2, 4, 6, 8]);
+}