From f6a8c3afb5b2c0cb1be044b9dc4368bfc8403991 Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Thu, 2 Nov 2023 16:03:26 +0000
Subject: [PATCH] Add real implementation of _xgetbv()

---
 src/inline_asm.rs          | 80 ++++++++++++++++++++++++++++++++++++++
 src/intrinsics/llvm_x86.rs | 11 ++----
 2 files changed, 83 insertions(+), 8 deletions(-)

diff --git a/src/inline_asm.rs b/src/inline_asm.rs
index ee7d5bcc9f7..ce0eecca8a8 100644
--- a/src/inline_asm.rs
+++ b/src/inline_asm.rs
@@ -729,3 +729,83 @@ fn call_inline_asm<'tcx>(
         place.write_cvalue(fx, CValue::by_val(value, place.layout()));
     }
 }
+
+pub(crate) fn codegen_xgetbv<'tcx>(
+    fx: &mut FunctionCx<'_, '_, 'tcx>,
+    xcr_no: Value,
+    ret: CPlace<'tcx>,
+) {
+    // FIXME add .eh_frame unwind info directives
+
+    let operands = vec![
+        CInlineAsmOperand::In {
+            reg: InlineAsmRegOrRegClass::Reg(InlineAsmReg::X86(X86InlineAsmReg::cx)),
+            value: xcr_no,
+        },
+        CInlineAsmOperand::Out {
+            reg: InlineAsmRegOrRegClass::Reg(InlineAsmReg::X86(X86InlineAsmReg::ax)),
+            late: true,
+            place: Some(ret),
+        },
+        CInlineAsmOperand::Out {
+            reg: InlineAsmRegOrRegClass::Reg(InlineAsmReg::X86(X86InlineAsmReg::dx)),
+            late: true,
+            place: None,
+        },
+    ];
+    let options = InlineAsmOptions::NOSTACK | InlineAsmOptions::PURE | InlineAsmOptions::NOMEM;
+
+    let mut inputs = Vec::new();
+    let mut outputs = Vec::new();
+
+    let mut asm_gen = InlineAssemblyGenerator {
+        tcx: fx.tcx,
+        arch: fx.tcx.sess.asm_arch.unwrap(),
+        enclosing_def_id: fx.instance.def_id(),
+        template: &[InlineAsmTemplatePiece::String(
+            "
+            xgetbv
+            // out = rdx << 32 | rax
+            shl rdx, 32
+            or rax, rdx
+            "
+            .to_string(),
+        )],
+        operands: &operands,
+        options,
+        registers: Vec::new(),
+        stack_slots_clobber: Vec::new(),
+        stack_slots_input: Vec::new(),
+        stack_slots_output: Vec::new(),
+        stack_slot_size: Size::from_bytes(0),
+    };
+    asm_gen.allocate_registers();
+    asm_gen.allocate_stack_slots();
+
+    let inline_asm_index = fx.cx.inline_asm_index.get();
+    fx.cx.inline_asm_index.set(inline_asm_index + 1);
+    let asm_name = format!(
+        "__inline_asm_{}_n{}",
+        fx.cx.cgu_name.as_str().replace('.', "__").replace('-', "_"),
+        inline_asm_index
+    );
+
+    let generated_asm = asm_gen.generate_asm_wrapper(&asm_name);
+    fx.cx.global_asm.push_str(&generated_asm);
+
+    for (i, operand) in operands.iter().enumerate() {
+        match operand {
+            CInlineAsmOperand::In { reg: _, value } => {
+                inputs.push((asm_gen.stack_slots_input[i].unwrap(), *value));
+            }
+            CInlineAsmOperand::Out { reg: _, late: _, place } => {
+                if let Some(place) = place {
+                    outputs.push((asm_gen.stack_slots_output[i].unwrap(), *place));
+                }
+            }
+            _ => unreachable!(),
+        }
+    }
+
+    call_inline_asm(fx, &asm_name, asm_gen.stack_slot_size, inputs, outputs);
+}
diff --git a/src/intrinsics/llvm_x86.rs b/src/intrinsics/llvm_x86.rs
index ea5997a14bb..6fd85ab8bf1 100644
--- a/src/intrinsics/llvm_x86.rs
+++ b/src/intrinsics/llvm_x86.rs
@@ -20,16 +20,11 @@ pub(crate) fn codegen_x86_llvm_intrinsic_call<'tcx>(
 
         // Used by is_x86_feature_detected!();
         "llvm.x86.xgetbv" => {
-            // FIXME use the actual xgetbv instruction
-            intrinsic_args!(fx, args => (v); intrinsic);
+            intrinsic_args!(fx, args => (xcr_no); intrinsic);
 
-            let v = v.load_scalar(fx);
+            let xcr_no = xcr_no.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)));
+            crate::inline_asm::codegen_xgetbv(fx, xcr_no, ret);
         }
 
         "llvm.x86.sse.cmp.ps" | "llvm.x86.sse2.cmp.pd" => {