[Clang][Driver] Add new flags to control IR verification

Author: mizvekov

clang/docs/ReleaseNotes.rst

@@ -146,6 +146,13 @@ Non-comprehensive list of changes in this release
 
 New Compiler Flags
 ------------------
+* ``-fverify-intermediate-code`` and it's complement ``-fno-verify-intermediate-code``.
+  Enables or disables verification of the generated LLVM IR.
+  It's strongly encouraged to enable this verification, as it can catch hard to
+  find code generation bugs.
+  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.
 
 Deprecated Compiler Flags
 -------------------------

clang/include/clang/Driver/Options.td

@@ -1905,6 +1905,12 @@ defm safe_buffer_usage_suggestions : BoolFOption<"safe-buffer-usage-suggestions"
   PosFlag<SetTrue, [], [ClangOption, CC1Option],
           "Display suggestions to update code associated with -Wunsafe-buffer-usage warnings">,
   NegFlag<SetFalse>>;
+def fverify_intermediate_code : Flag<["-"], "fverify-intermediate-code">,
+  Group<f_clang_Group>, Visibility<[ClangOption, CLOption, DXCOption]>,
+  HelpText<"Enable verification of LLVM IR">, Flags<[NoXarchOption]>;
+def fno_verify_intermediate_code : Flag<["-"], "fno-verify-intermediate-code">,
+  Group<f_clang_Group>, Visibility<[ClangOption, CLOption, DXCOption]>,
+  HelpText<"Disable verification of LLVM IR">, Flags<[NoXarchOption]>;
 def fdiscard_value_names : Flag<["-"], "fdiscard-value-names">,
   Group<f_clang_Group>, Visibility<[ClangOption, DXCOption]>,
   HelpText<"Discard value names in LLVM IR">, Flags<[NoXarchOption]>;

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5150,9 +5150,11 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   const bool IsAssertBuild = true;
 #endif
 
-  // Disable the verification pass in -asserts builds.
-  if (!IsAssertBuild)
+  // Disable the verification pass in asserts builds unless otherwise specified.
+  if (Args.hasFlag(options::OPT_fno_verify_intermediate_code,
+                   options::OPT_fverify_intermediate_code, !IsAssertBuild)) {
     CmdArgs.push_back("-disable-llvm-verifier");
+  }
 
   // Discard value names in assert builds unless otherwise specified.
   if (Args.hasFlag(options::OPT_fdiscard_value_names,

clang/test/Driver/clang_f_opts.c

@@ -520,6 +520,11 @@
 // CHECK-COVERAGE-COMPILATION-DIR: "-fcoverage-compilation-dir=."
 // CHECK-COVERAGE-COMPILATION-DIR-NOT: "-ffile-compilation-dir=."
 
+// RUN: %clang -### -S -fverify-intermediate-code %s 2>&1 | FileCheck -check-prefix=CHECK-VERIFY-INTERMEDIATE-CODE %s
+// RUN: %clang -### -S -fno-verify-intermediate-code %s 2>&1 | FileCheck -check-prefix=CHECK-NO-VERIFY-INTERMEDIATE-CODE %s
+// CHECK-VERIFY-INTERMEDIATE-CODE-NOT: "-disable-llvm-verifier"
+// CHECK-NO-VERIFY-INTERMEDIATE-CODE: "-disable-llvm-verifier"
+
 // 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"