[COFF, ARM64] Add MS intrinsics: __getReg, _ReadStatusReg, _WriteStatusReg

[mgrang]

Summary

Added declarations for the intrinsics in intrin.h. These are defined in MSVC libs and are needed for
certain spec2000 benchmarks.

[mstorsjo]

In MSVC, these ones seem to be declared in intrin.h, not in the arm64intr.h subheader, so to match closely perhaps we should declare them there as well?

The test, arm64-microsoft-intrinsics.c, doesn't actually include intrin.h nor arm64intr.h, so this test doesn't actually test anything of what this changes (this test would pass just as well before this change). Not sure if a test for this is mandatory or how we handle tests for lib/Headers though.

[mgrang]

Thanks @mstorsjo. I have addressed your comments.

[rnk]

This just adds declarations. Are these functions provided by some Windows runtime library? Don't you need to implement the intrinsics somewhere in order for the apps that use them to run or link? Ideally, they should be implemented as builtins.

[mgrang]

Will abandon this patch since I have implementations of these which I will upstream soon.

[dmajor]

In D51204#1253230, @mgrang wrote:

Will abandon this patch since I have implementations of these which I will upstream soon.

Just to link up the reviews: these landed in D52838 and D53115. (Thanks @mgrang!)

[glandium]

In D51204#1271564, @dmajor wrote:

In D51204#1253230, @mgrang wrote:

Will abandon this patch since I have implementations of these which I will upstream soon.

Just to link up the reviews: these landed in D52838 and D53115. (Thanks @mgrang!)

Except not really... D53115 got the types wrong, and used int instead of __int64.

[glandium]

Opened D57636

lib/Headers/intrin.h

 }
 static __inline__ void __DEFAULT_FN_ATTRS
 __nop(void) {
   __asm__ volatile ("nop");
 }
 #endif
 
 /*----------------------------------------------------------------------------*\
+|* MS AArch64 specific
+\*----------------------------------------------------------------------------*/
+#if defined(__aarch64__)
+unsigned __int64 __getReg(int);
+__int64 _ReadStatusReg(int);
+void _WriteStatusReg(int, __int64);
+#endif
+
+/*----------------------------------------------------------------------------*\
 |* Privileged intrinsics
 \*----------------------------------------------------------------------------*/
 #if defined(__i386__) || defined(__x86_64__)
 static __inline__ unsigned __int64 __DEFAULT_FN_ATTRS
 __readmsr(unsigned long __register) {
   // Loads the contents of a 64-bit model specific register (MSR) specified in
   // the ECX register into registers EDX:EAX. The EDX register is loaded with
   // the high-order 32 bits of the MSR and the EAX register is loaded with the

test/Headers/arm64-ms-intrin.cpp

+// RUN: %clang_cc1 -triple arm64-windows -S -emit-llvm -o - %s \
+// RUN: -fms-compatibility -fms-compatibility-version=17.00 \
+// RUN: -isystem %S/Inputs/include 2>&1 | FileCheck %s
+
+#include <intrin.h>
+
+unsigned __int64 check__getReg() {
+  return __getReg(1);
+}
+// CHECK: call i64 @__getReg(i32 1)
+
+__int64 check_ReadStatusReg() {
+  return _ReadStatusReg(1);
+}
+// CHECK: call i64 @_ReadStatusReg(i32 1)
+
+void check_WriteStatusReg() {
+  __int64 x;
+  _WriteStatusReg(1, x);
+}
+// CHECK: call void @_WriteStatusReg(i32 1, i64 %0)