From deedd2888175224b48b00eec4c74f0ab8625eb1e Mon Sep 17 00:00:00 2001
From: Antoni Boucher <bouanto@zoho.com>
Date: Thu, 4 Aug 2022 20:11:36 -0400
Subject: [PATCH] Fix the mxcsr builtins

---
 src/builder.rs        |  3 ++-
 src/intrinsic/llvm.rs | 24 +++++++++++++++++++++++-
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/builder.rs b/src/builder.rs
index 616fc01b00c..bcbaad39044 100644
--- a/src/builder.rs
+++ b/src/builder.rs
@@ -279,6 +279,7 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
         let gcc_func = func_ptr.get_type().dyncast_function_ptr_type().expect("function ptr");
         let func_name = format!("{:?}", func_ptr);
         let previous_arg_count = args.len();
+        let orig_args = args;
         let args = llvm::adjust_intrinsic_arguments(&self, gcc_func, args.into(), &func_name);
         let args_adjusted = args.len() != previous_arg_count;
         let args = self.check_ptr_call("call", func_ptr, &*args);
@@ -292,7 +293,7 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
         if return_type != void_type {
             unsafe { RETURN_VALUE_COUNT += 1 };
             let return_value = self.cx.context.new_call_through_ptr(None, func_ptr, &args);
-            let return_value = llvm::adjust_intrinsic_return_value(&self, return_value, &func_name, &args, args_adjusted);
+            let return_value = llvm::adjust_intrinsic_return_value(&self, return_value, &func_name, &args, args_adjusted, orig_args);
             let result = current_func.new_local(None, return_value.get_type(), &format!("ptrReturnValue{}", unsafe { RETURN_VALUE_COUNT }));
             self.block.add_assignment(None, result, return_value);
             result.to_rvalue()
diff --git a/src/intrinsic/llvm.rs b/src/intrinsic/llvm.rs
index f00c1b30109..20f500e34e9 100644
--- a/src/intrinsic/llvm.rs
+++ b/src/intrinsic/llvm.rs
@@ -1,6 +1,7 @@
 use std::borrow::Cow;
 
 use gccjit::{Function, FunctionPtrType, RValue, ToRValue, UnaryOp};
+use rustc_codegen_ssa::traits::BuilderMethods;
 
 use crate::{context::CodegenCx, builder::Builder};
 
@@ -277,6 +278,15 @@ pub fn adjust_intrinsic_arguments<'a, 'b, 'gcc, 'tcx>(builder: &Builder<'a, 'gcc
                 *arg3 = builder.context.new_unary_op(None, UnaryOp::Minus, arg3.get_type(), *arg3);
                 args = new_args.into();
             },
+            "__builtin_ia32_ldmxcsr" => {
+                // The builtin __builtin_ia32_ldmxcsr takes an integer value while llvm.x86.sse.ldmxcsr takes a pointer,
+                // so dereference the pointer.
+                let mut new_args = args.to_vec();
+                let uint_ptr_type = builder.uint_type.make_pointer();
+                let arg1 = builder.context.new_cast(None, args[0], uint_ptr_type);
+                new_args[0] = arg1.dereference(None).to_rvalue();
+                args = new_args.into();
+            },
             _ => (),
         }
     }
@@ -284,7 +294,7 @@ pub fn adjust_intrinsic_arguments<'a, 'b, 'gcc, 'tcx>(builder: &Builder<'a, 'gcc
     args
 }
 
-pub fn adjust_intrinsic_return_value<'a, 'gcc, 'tcx>(builder: &Builder<'a, 'gcc, 'tcx>, mut return_value: RValue<'gcc>, func_name: &str, args: &[RValue<'gcc>], args_adjusted: bool) -> RValue<'gcc> {
+pub fn adjust_intrinsic_return_value<'a, 'gcc, 'tcx>(builder: &Builder<'a, 'gcc, 'tcx>, mut return_value: RValue<'gcc>, func_name: &str, args: &[RValue<'gcc>], args_adjusted: bool, orig_args: &[RValue<'gcc>]) -> RValue<'gcc> {
     match func_name {
         "__builtin_ia32_vfmaddss3_round" | "__builtin_ia32_vfmaddsd3_round" => {
             #[cfg(feature="master")]
@@ -306,6 +316,18 @@ pub fn adjust_intrinsic_return_value<'a, 'gcc, 'tcx>(builder: &Builder<'a, 'gcc,
                 return_value = builder.context.new_struct_constructor(None, struct_type.as_type(), None, &[return_value, last_arg.dereference(None).to_rvalue()]);
             }
         },
+        "__builtin_ia32_stmxcsr" => {
+            // The builtin __builtin_ia32_stmxcsr returns a value while llvm.x86.sse.stmxcsr writes
+            // the result in its pointer argument.
+            // We removed the argument since __builtin_ia32_stmxcsr takes no arguments, so we need
+            // to get back the original argument to get the pointer we need to write the result to.
+            let uint_ptr_type = builder.uint_type.make_pointer();
+            let ptr = builder.context.new_cast(None, orig_args[0], uint_ptr_type);
+            builder.llbb().add_assignment(None, ptr.dereference(None), return_value);
+            // The return value was assigned to the result pointer above. In order to not call the
+            // builtin twice, we overwrite the return value with a dummy value.
+            return_value = builder.context.new_rvalue_zero(builder.int_type);
+        },
         _ => (),
     }