add support for Elbrus 2000 (e2k)

[SSE4]

Summary

original patch from:
https://bugs.llvm.org/show_bug.cgi?id=42828
https://lists.gnu.org/archive/html/config-patches/2015-03/msg00000.html

fixes only build for e2k, it doesn't include support for e2k backend

• update config.guess to include e2k-linux
• fix "#error You need to define CycleTimer for your OS and CPU" for e2k
• update root CMakeLists.txt to recognize e2k architecture
• compiler flag "-fdiagnostics-color" is not supported by MCST LCC compiler, add flag only if supported
• attribute "[[clang::warn_unused_result]]" is incorrectly reported as supported by MCST LCC compiler

[SSE4]

add support for Elbrus 2000 (e2k)

[lebedev.ri]

Please can you submit llvm/utils/benchmark/ changes upstream first?

[SSE4]

In D95940#2561525, @lebedev.ri wrote:

Please can you submit llvm/utils/benchmark/ changes upstream first?

submitted: https://github.com/google/benchmark/pull/1091

[lebedev.ri]

@SSE4 please abandon this review (also, i can't even remove myself as reviewer since you disabled editing here)

llvm/cmake/config-ix.cmake

 elseif (LLVM_NATIVE_ARCH MATCHES "wasm32")
   set(LLVM_NATIVE_ARCH WebAssembly)
 elseif (LLVM_NATIVE_ARCH MATCHES "wasm64")
   set(LLVM_NATIVE_ARCH WebAssembly)
 elseif (LLVM_NATIVE_ARCH MATCHES "riscv32")
   set(LLVM_NATIVE_ARCH RISCV)
 elseif (LLVM_NATIVE_ARCH MATCHES "riscv64")
   set(LLVM_NATIVE_ARCH RISCV)
+elseif (LLVM_NATIVE_ARCH MATCHES "e2k")
+  set(LLVM_NATIVE_ARCH E2K)
 else ()
   message(FATAL_ERROR "Unknown architecture ${LLVM_NATIVE_ARCH}")
 endif ()
 
 # If build targets includes "host", then replace with native architecture.
 list(FIND LLVM_TARGETS_TO_BUILD "host" idx)
 if( NOT idx LESS 0 )
   list(REMOVE_AT LLVM_TARGETS_TO_BUILD ${idx})

llvm/cmake/config.guess

EOF
   echo cris-axis-linux-gnu
   exit ;;
     crisv32:Linux:*:*)
   echo crisv32-axis-linux-gnu
   exit ;;
     frv:Linux:*:*)
   echo frv-unknown-linux-gnu
   exit ;;
+    e2k:Linux:*:*)
+  echo ${UNAME_MACHINE}-unknown-linux-gnu
+  exit ;;
     i*86:Linux:*:*)
   LIBC=gnu
   eval $set_cc_for_build
   sed 's/^ //' << EOF >$dummy.c
   #ifdef __dietlibc__
   LIBC=dietlibc
   #endif
 EOF

llvm/cmake/modules/HandleLLVMOptions.cmake

 add_definitions( -D__STDC_LIMIT_MACROS )
 
 # clang and gcc don't default-print colored diagnostics when invoked from Ninja.
 if (UNIX AND
     CMAKE_GENERATOR STREQUAL "Ninja" AND
     (CMAKE_CXX_COMPILER_ID MATCHES "Clang" OR
      (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND
       NOT (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.9))))
-  append("-fdiagnostics-color" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+  add_flag_if_supported("-fdiagnostics-color" FDIAGNOSTICS_COLOR)
 endif()
 
 # lld doesn't print colored diagnostics when invoked from Ninja
 if (UNIX AND CMAKE_GENERATOR STREQUAL "Ninja")
   include(CheckLinkerFlag)
   check_linker_flag("-Wl,--color-diagnostics" LINKER_SUPPORTS_COLOR_DIAGNOSTICS)
   append_if(LINKER_SUPPORTS_COLOR_DIAGNOSTICS "-Wl,--color-diagnostics"
     CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)

llvm/include/llvm/Support/Compiler.h

 //===-- llvm/Support/Compiler.h - Compiler abstraction support --*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //

 #endif
 
 /// LLVM_NODISCARD - Warn if a type or return value is discarded.
 
 // Use the 'nodiscard' attribute in C++17 or newer mode.
 #if defined(__cplusplus) && __cplusplus > 201402L && LLVM_HAS_CPP_ATTRIBUTE(nodiscard)
 #define LLVM_NODISCARD [[nodiscard]]
 #elif LLVM_HAS_CPP_ATTRIBUTE(clang::warn_unused_result)
+#if defined(__LCC__) && defined(__e2k__)
+#define LLVM_NODISCARD
+#else
 #define LLVM_NODISCARD [[clang::warn_unused_result]]
+#endif
 // Clang in C++14 mode claims that it has the 'nodiscard' attribute, but also
 // warns in the pedantic mode that 'nodiscard' is a C++17 extension (PR33518).
 // Use the 'nodiscard' attribute in C++14 mode only with GCC.
 // TODO: remove this workaround when PR33518 is resolved.
 #elif defined(__GNUC__) && LLVM_HAS_CPP_ATTRIBUTE(nodiscard)
 #define LLVM_NODISCARD [[nodiscard]]
 #else
 #define LLVM_NODISCARD

llvm/utils/benchmark/src/cycleclock.h

 // ----------------------------------------------------------------------
 // CycleClock
 //    A CycleClock tells you the current time in Cycles.  The "time"
 //    is actually time since power-on.  This is like time() but doesn't
 //    involve a system call and is much more precise.
 //
 // NOTE: Not all cpu/platform/kernel combinations guarantee that this
 // clock increments at a constant rate or is synchronized across all logical
asm volatile(
       "and %1, %1, %0\n"
       : "=r"(cycles_hi0), "=r"(cycles_lo), "=r"(cycles_hi1));
   return (static_cast<uint64_t>(cycles_hi1) << 32) | cycles_lo;
 #else
   uint64_t cycles;
   asm volatile("rdcycle %0" : "=r"(cycles));
   return cycles;
 #endif
+#elif defined(__e2k__) || defined(__elbrus__)
+  struct timeval tv;
+  gettimeofday(&tv, nullptr);
+  return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
 #else
 // The soft failover to a generic implementation is automatic only for ARM.
 // For other platforms the developer is expected to make an attempt to create
 // a fast implementation and use generic version if nothing better is available.
 #error You need to define CycleTimer for your OS and CPU
 #endif
 }
 }  // end namespace cycleclock
 }  // end namespace benchmark
 
 #endif  // BENCHMARK_CYCLECLOCK_H_