ASM: Record all assembler id information

Previously, `CMAKE_ASM${DIALECT}_COMPILER_FRONTEND_VARIANT` and
`CMAKE_ASM${DIALECT}_SIMULATE_ID` were not saved in with the build
configuration. As a result, these were left unpopulated on re-configure.
This is particularly problematic when `clang-cl` is used as the
assembler on Windows, since CMake would mistakenly identify the build as
being "GCC on Windows", resulting in include paths being passed with
forward slashes on re-configure, causing a full rebuild.

Fix the issue by saving the information so it persists across
re-configures.

Modules/CMakeASMCompiler.cmake.in

@@ -18,6 +18,8 @@ set(CMAKE_ASM@ASM_DIALECT@_COMPILER_LOADED 1)
 set(CMAKE_ASM@ASM_DIALECT@_COMPILER_ID "@_CMAKE_ASM_COMPILER_ID@")
 set(CMAKE_ASM@ASM_DIALECT@_COMPILER_VERSION "@_CMAKE_ASM_COMPILER_VERSION@")
 set(CMAKE_ASM@ASM_DIALECT@_COMPILER_ENV_VAR "@_CMAKE_ASM_COMPILER_ENV_VAR@")
+set(CMAKE_ASM@ASM_DIALECT@_COMPILER_FRONTEND_VARIANT "@_CMAKE_ASM_COMPILER_FRONTEND_VARIANT@")
+set(CMAKE_ASM@ASM_DIALECT@_SIMULATE_ID "@_CMAKE_ASM_SIMULATE_ID@")
 @_SET_CMAKE_ASM_COMPILER_ID_VENDOR_MATCH@
 set(CMAKE_ASM@ASM_DIALECT@_COMPILER_ARCHITECTURE_ID "@_CMAKE_ASM_COMPILER_ARCHITECTURE_ID@")
 @_SET_CMAKE_ASM_COMPILER_SYSROOT@

Modules/CMakeDetermineASMCompiler.cmake

@@ -297,7 +297,7 @@ endif()
 # configure variables set in this file for fast reload later on
 block()
   foreach(_var IN ITEMS
-      # Keep in sync with Internal/CMakeTestASMLinker.
+      # Keep in sync with Internal/CMakeInspectASMLinker.
       COMPILER
       COMPILER_ID
       COMPILER_ARG1
@@ -306,6 +306,8 @@ block()
       COMPILER_RANLIB
       COMPILER_VERSION
       COMPILER_ARCHITECTURE_ID
+      COMPILER_FRONTEND_VARIANT
+      SIMULATE_ID
       )
     set(_CMAKE_ASM_${_var} "${CMAKE_ASM${ASM_DIALECT}_${_var}}")
   endforeach()

Modules/Internal/CMakeInspectASMLinker.cmake

@@ -14,6 +14,8 @@ block()
       COMPILER_RANLIB
       COMPILER_VERSION
       COMPILER_ARCHITECTURE_ID
+      COMPILER_FRONTEND_VARIANT
+      SIMULATE_ID
       # Linker information.
       COMPILER_LINKER
       COMPILER_LINKER_ID

Tests/RunCMake/CMakeLists.txt

@@ -393,6 +393,7 @@ if(CMAKE_GENERATOR MATCHES "Make|Ninja")
   add_RunCMake_test(Color)
 endif()
 add_RunCMake_test(CompilerChange)
+add_RunCMake_test(CompilerInfo -DPSEUDO_ASM=$<TARGET_FILE:pseudo_asm>)
 add_RunCMake_test(CompilerNotFound)
 if(DEFINED CMake_TEST_OBJC)
   list(APPEND CMake_TEST_LANG_VARS -DCMake_TEST_OBJC=${CMake_TEST_OBJC})
@@ -1288,6 +1289,7 @@ if(CMake_TEST_FindMatlab OR CMake_TEST_FindMatlab_MCR OR (NOT "${CMake_TEST_Find
   set_property(TEST RunCMake.FindMatlab APPEND PROPERTY LABELS "Matlab")
 endif()
 
+add_executable(pseudo_asm pseudo_asm.c)
 add_executable(pseudo_emulator pseudo_emulator.c)
 add_executable(pseudo_emulator_custom_command pseudo_emulator_custom_command.c)
 add_executable(pseudo_emulator_custom_command_arg pseudo_emulator_custom_command_arg.c)

Tests/RunCMake/CompilerInfo/ASM-check-common.cmake

@@ -0,0 +1,17 @@
+# The information file is what a later configure reloads, so load it the same
+# way and check that every field detection computed was recorded.  The caller
+# sets the expect_* values for the assembler flavor under test.
+include("${RunCMake_TEST_BINARY_DIR}/CMakeFiles/${CMAKE_VERSION}/CMakeASMCompiler.cmake")
+
+foreach(var
+    CMAKE_ASM_COMPILER_ID
+    CMAKE_ASM_SIMULATE_ID
+    CMAKE_ASM_COMPILER_FRONTEND_VARIANT
+    )
+  if(NOT "${${var}}" STREQUAL "${expect_${var}}")
+    string(APPEND RunCMake_TEST_FAILED
+      "${var} was not recorded in the assembler information file:\n"
+      "  expected: '${expect_${var}}'\n"
+      "  reloaded: '${${var}}'\n")
+  endif()
+endforeach()

Tests/RunCMake/CompilerInfo/ASM-clang-cl-check.cmake

@@ -0,0 +1,4 @@
+set(expect_CMAKE_ASM_COMPILER_ID "Clang")
+set(expect_CMAKE_ASM_SIMULATE_ID "MSVC")
+set(expect_CMAKE_ASM_COMPILER_FRONTEND_VARIANT "MSVC")
+include("${RunCMake_SOURCE_DIR}/ASM-check-common.cmake")

Tests/RunCMake/CompilerInfo/ASM-clang-cl.cmake

@@ -0,0 +1 @@
+include("${CMAKE_CURRENT_SOURCE_DIR}/ASM-common.cmake")

Tests/RunCMake/CompilerInfo/ASM-clang-gnu-check.cmake

@@ -0,0 +1,5 @@
+# A GNU-like command-line leaves the simulate id empty.
+set(expect_CMAKE_ASM_COMPILER_ID "Clang")
+set(expect_CMAKE_ASM_SIMULATE_ID "")
+set(expect_CMAKE_ASM_COMPILER_FRONTEND_VARIANT "GNU")
+include("${RunCMake_SOURCE_DIR}/ASM-check-common.cmake")

Tests/RunCMake/CompilerInfo/ASM-clang-gnu.cmake

@@ -0,0 +1 @@
+include("${CMAKE_CURRENT_SOURCE_DIR}/ASM-common.cmake")

Tests/RunCMake/CompilerInfo/ASM-common.cmake

@@ -0,0 +1,15 @@
+# Assembler information is detected once and written to
+# CMakeASM<dialect>Compiler.cmake, then reloaded from that file on every later
+# configure.  A field that detection computes but the file does not record
+# comes back empty, so a re-configure sees a different assembler than the one
+# that was detected.  The -check script reloads the file and verifies this.
+
+enable_language(ASM)
+
+# Detection must identify the assembler in the first place.
+if(NOT CMAKE_ASM_COMPILER_ID)
+  message(SEND_ERROR "CMAKE_ASM_COMPILER_ID was not detected")
+endif()
+if(NOT CMAKE_ASM_COMPILER_FRONTEND_VARIANT)
+  message(SEND_ERROR "CMAKE_ASM_COMPILER_FRONTEND_VARIANT was not detected")
+endif()

Tests/RunCMake/CompilerInfo/CMakeLists.txt

@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 4.4)
+project(${RunCMake_TEST} NONE)
+include(${RunCMake_TEST}.cmake)

Tests/RunCMake/CompilerInfo/RunCMakeTest.cmake

@@ -0,0 +1,14 @@
+include(RunCMake)
+
+block()
+  # The stand-in assembler reports an MSVC-like command-line by default and a
+  # GNU-like one when PSEUDO_ASM_GNU is set, which selects the two branches of
+  # assembler identification that populate these fields differently.
+  set(RunCMake_TEST_OPTIONS "-DCMAKE_ASM_COMPILER=${PSEUDO_ASM}")
+
+  run_cmake(ASM-clang-cl)
+
+  set(ENV{PSEUDO_ASM_GNU} 1)
+  run_cmake(ASM-clang-gnu)
+  unset(ENV{PSEUDO_ASM_GNU})
+endblock()

Tests/RunCMake/pseudo_asm.c

@@ -0,0 +1,30 @@
+#ifndef _CRT_SECURE_NO_WARNINGS
+#  define _CRT_SECURE_NO_WARNINGS
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/*
+  Usage: pseudo_asm [--version] [-?]
+
+  --version: print a banner that identifies this program as Clang.
+  -?: return 0 for MSVC-like command-line, 1 for GNU-like command-line,
+      depending on the presence of the PSEUDO_ASM_GNU environment variable.
+*/
+int main(int argc, char* argv[])
+{
+  int i;
+  for (i = 1; i < argc; ++i) {
+    if (strcmp(argv[i], "--version") == 0) {
+      printf("clang version 99.0.0 (pseudo_asm)\n");
+      return 0;
+    }
+    if (strcmp(argv[i], "-?") == 0) {
+      char const* gnu = getenv("PSEUDO_ASM_GNU");
+      return (gnu && *gnu) ? 1 : 0;
+    }
+  }
+  return 0;
+}