[Clang][Driver] Add new flags to control machine instruction verification

Author: mizvekov

clang/docs/ReleaseNotes.rst

@@ -206,6 +206,13 @@ New Compiler Flags
   Since enabling the verifier adds a non-trivial cost of a few percent impact on
   build times, it's disabled by default, unless your LLVM distribution itself is
   compiled with runtime checks enabled.
+* ``-fverify-machine-code`` and its complement ``-fno-verify-machine-code``.
+  Enable or disable the verification of the generated machine code.
+  Users can pass this to turn on extra verification to catch certain types of
+  compiler bugs at the cost of extra compile time.
+  This verifier adds a huge overhead to compile time, it's expected that build times
+  can double, so this is disabled by default.
+  This flag is currently limited to non-LTO builds.
 * ``-fkeep-system-includes`` modifies the behavior of the ``-E`` option,
   preserving ``#include`` directives for "system" headers instead of copying
   the preprocessed text to the output. This can greatly reduce the size of the

clang/include/clang/Driver/Options.td

@@ -1925,6 +1925,12 @@ def fverify_intermediate_code : Flag<["-"], "fverify-intermediate-code">,
 def fno_verify_intermediate_code : Flag<["-"], "fno-verify-intermediate-code">,
   Group<f_clang_Group>, Visibility<[ClangOption, CLOption, DXCOption]>,
   HelpText<"Disable verification of LLVM IR">;
+def fverify_machine_code : Flag<["-"], "fverify-machine-code">,
+  Group<f_clang_Group>, Visibility<[ClangOption, CLOption, DXCOption]>,
+  HelpText<"Enable verification of generated machine code">;
+def fno_verify_machine_code : Flag<["-"], "fno-verify-machine-code">,
+  Group<f_clang_Group>, Visibility<[ClangOption, CLOption, DXCOption]>,
+  HelpText<"Disable verification of generated machine code">;
 def fdiscard_value_names : Flag<["-"], "fdiscard-value-names">,
   Group<f_clang_Group>, Visibility<[ClangOption, DXCOption]>,
   HelpText<"Discard value names in LLVM IR">;

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5175,6 +5175,14 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("-disable-llvm-verifier");
   }
 
+  // Enable the machine code verification pass. Note that this is force enabled
+  // elsewhere with LLVM_ENABLE_EXPENSIVE_CHECKS.
+  if (Args.hasFlag(options::OPT_fverify_machine_code,
+                   options::OPT_fno_verify_machine_code, false)) {
+    CmdArgs.push_back("-mllvm");
+    CmdArgs.push_back("-verify-machineinstrs");
+  }
+
   // Discard value names in assert builds unless otherwise specified.
   if (Args.hasFlag(options::OPT_fdiscard_value_names,
                    options::OPT_fno_discard_value_names, !IsAssertBuild)) {

clang/test/Driver/clang_f_opts.c

@@ -525,6 +525,11 @@
 // CHECK-VERIFY-INTERMEDIATE-CODE-NOT: "-disable-llvm-verifier"
 // CHECK-NO-VERIFY-INTERMEDIATE-CODE: "-disable-llvm-verifier"
 
+// RUN: %clang -### -S -fverify-machine-code %s 2>&1 | FileCheck -check-prefix=CHECK-VERIFY-MACHINE-CODE %s
+// RUN: %clang -### -S -fno-verify-machine-code %s 2>&1 | FileCheck -check-prefix=CHECK-NO-VERIFY-MACHINE-CODE %s
+// CHECK-VERIFY-MACHINE-CODE: "-mllvm" "-verify-machineinstrs"
+// CHECK-NO-VERIFY-MACHINE-CODE-NOT: "-mllvm" "-verify-machineinstrs"
+
 // RUN: %clang -### -S -fdiscard-value-names %s 2>&1 | FileCheck -check-prefix=CHECK-DISCARD-NAMES %s
 // RUN: %clang -### -S -fno-discard-value-names %s 2>&1 | FileCheck -check-prefix=CHECK-NO-DISCARD-NAMES %s
 // CHECK-DISCARD-NAMES: "-discard-value-names"