From 8cad29a5297712e7828a8ba2f87c9de3903f86cd Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Fri, 23 Jun 2023 10:05:18 +0000
Subject: [PATCH] Implement _xgetbv

---
 src/intrinsics/llvm_x86.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/intrinsics/llvm_x86.rs b/src/intrinsics/llvm_x86.rs
index 980d3262b67..5b2b3ab2b62 100644
--- a/src/intrinsics/llvm_x86.rs
+++ b/src/intrinsics/llvm_x86.rs
@@ -18,6 +18,20 @@ pub(crate) fn codegen_x86_llvm_intrinsic_call<'tcx>(
             // Spin loop hint
         }
 
+        // Used by is_x86_feature_detected!();
+        "llvm.x86.xgetbv" => {
+            // FIXME use the actual xgetbv instruction
+            intrinsic_args!(fx, args => (v); intrinsic);
+
+            let v = v.load_scalar(fx);
+
+            // As of writing on XCR0 exists
+            fx.bcx.ins().trapnz(v, TrapCode::UnreachableCodeReached);
+
+            let res = fx.bcx.ins().iconst(types::I64, 1 /* bit 0 must be set */);
+            ret.write_cvalue(fx, CValue::by_val(res, fx.layout_of(fx.tcx.types.i64)));
+        }
+
         // Used by `_mm_movemask_epi8` and `_mm256_movemask_epi8`
         "llvm.x86.sse2.pmovmskb.128"
         | "llvm.x86.avx2.pmovmskb"