add shim for _mm512_permutexvar_epi32

Author: folkertdev

src/tools/miri/src/shims/x86/avx512.rs

@@ -95,6 +95,26 @@ pub(super) trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
                 pmaddbw(this, left, right, dest)?;
             }
+            // Used to implement the _mm512_permutexvar_epi32 function.
+            "permvar.si.512" => {
+                let [left, right] =
+                    this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
+
+                let (left, left_len) = this.project_to_simd(left)?;
+                let (right, right_len) = this.project_to_simd(right)?;
+                let (dest, dest_len) = this.project_to_simd(dest)?;
+
+                assert_eq!(dest_len, left_len);
+                assert_eq!(dest_len, right_len);
+
+                for i in 0..dest_len {
+                    let dest = this.project_index(&dest, i)?;
+                    let right = this.read_scalar(&this.project_index(&right, i)?)?.to_u32()?;
+                    let left = this.project_index(&left, (right & 0b1111).into())?;
+
+                    this.copy_op(&left, &dest)?;
+                }
+            }
             _ => return interp_ok(EmulateItemResult::NotSupported),
         }
         interp_ok(EmulateItemResult::NeedsReturn)

src/tools/miri/tests/pass/shims/x86/intrinsics-x86-avx512.rs

@@ -97,6 +97,52 @@ unsafe fn test_avx512() {
         assert_eq_m512i(r, e);
     }
     test_mm512_maddubs_epi16();
+
+    #[target_feature(enable = "avx512f")]
+    unsafe fn test_mm512_permutexvar_epi32() {
+        let a = _mm512_set_epi32(
+            15, 14, 13, 12, //
+            11, 10, 9, 8, //
+            7, 6, 5, 4, //
+            3, 2, 1, 0, //
+        );
+
+        let idx_identity = _mm512_set_epi32(
+            15, 14, 13, 12, //
+            11, 10, 9, 8, //
+            7, 6, 5, 4, //
+            3, 2, 1, 0, //
+        );
+        let r_id = _mm512_permutexvar_epi32(idx_identity, a);
+        assert_eq_m512i(r_id, a);
+
+        // Test some out-of-bounds indices.
+        let edge_cases = _mm512_set_epi32(
+            0,
+            -1,
+            -128,
+            i32::MIN,
+            15,
+            16,
+            128,
+            i32::MAX,
+            0,
+            -1,
+            -128,
+            i32::MIN,
+            15,
+            16,
+            128,
+            i32::MAX,
+        );
+
+        let r = _mm512_permutexvar_epi32(edge_cases, a);
+
+        let e = _mm512_set_epi32(0, 15, 0, 0, 15, 0, 0, 15, 0, 15, 0, 0, 15, 0, 0, 15);
+
+        assert_eq_m512i(r, e);
+    }
+    test_mm512_permutexvar_epi32();
 }
 
 // Some of the constants in the tests below are just bit patterns. They should not