Handle SIMD8/LONG recasts for LCL_FLD

Lowering needs to insert a `BITCAST` in the case of a `STORE_LCL_FLD` with mismatched `TYP_SIMD8`/`TYP_LONG` operands, just as for `STORE_LCL_VAR`.

2 files changed, 94 insertions, 0 deletions

diff --git a/tests/src/JIT/Regression/JitBlue/DevDiv_590358/DevDiv_590358.cs b/tests/src/JIT/Regression/JitBlue/DevDiv_590358/DevDiv_590358.cs
new file mode 100644
index 0000000000..dd690d1d52
--- /dev/null
+++ b/tests/src/JIT/Regression/JitBlue/DevDiv_590358/DevDiv_590358.cs
@@ -0,0 +1,57 @@
+using System;
+using System.Numerics;
+
+// In this test case, we have a struct S that contains a single Vector2 field (Vector),
+// with an implicit conversion from an array of float to S.
+// We inline a call to this op_Implicit, and then the constructor that it invokes.
+// The op_Implicit RET_EXPR is TYP_LONG, since that's how the value is returned from the method.
+// It is then stored to the Vector field which is TYP_SIMD8.
+//
+// Bug: The JIT had code to deal with this kind of retyping (which must be made explicit by
+//      Lowering, as the two types require different register types), when it involves locals
+//      (GT_LCL_VAR) but not fields of locals (GT_LCL_FLD).
+//
+// Perf Issue: What we wind up with is this: (V05 & V07 are both TYP_SIMD8, V01 is the struct type S
+//          V05 = *(TYP_SIMD8)numbers
+//          V07 = V05
+//          LCL_FLD(V01) = LCL_FLD(V07)  // Both re-typed as TYP_LONG
+// This generates:
+//          vmovsd   xmm0, qword ptr [rax+16]
+//          vmovsd   qword ptr[rsp + 28H], xmm0
+//          vmovsd   xmm0, qword ptr[rsp + 28H]
+//          vmovsd   qword ptr[rsp + 20H], xmm0
+//          vmovsd   xmm0, qword ptr[rsp + 20H]
+//          vmovsd   qword ptr[rsp + 30H], xmm0
+//
+// We should be able to elide these excessive copies and unnecessary retyping, producing close to this:
+//          vmovsd   xmm0, qword ptr [rax+16]
+//          vmovsd   qword ptr[rsp + 30H], xmm0
+
+namespace Repro
+{
+    class Program
+    {
+	    struct S
+	    {
+	        public Vector2 Vector;
+	        public S(float[] numbers)
+	        {
+		        Vector = new Vector2(numbers[0], numbers[1]);
+	        }
+	        public static implicit operator S(float[] numbers) => new S(numbers);
+	    }
+	    static int Main(string[] args)
+	    {
+	        S s = new float[] { 1.0f, 2.0f };
+	        Console.WriteLine(s.Vector);
+            if ((s.Vector.X != 1.0f) || (s.Vector.Y != 2.0f))
+            {
+                return -1;
+            }
+            else
+            {
+                return 100;
+            }
+	    }
+    }
+}
diff --git a/tests/src/JIT/Regression/JitBlue/DevDiv_590358/DevDiv_590358.csproj b/tests/src/JIT/Regression/JitBlue/DevDiv_590358/DevDiv_590358.csproj
new file mode 100644
index 0000000000..6d58ab0227
--- /dev/null
+++ b/tests/src/JIT/Regression/JitBlue/DevDiv_590358/DevDiv_590358.csproj
@@ -0,0 +1,37 @@
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+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
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+  <ItemGroup>
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