[clang] [CLang][Driver] Add new flags to control IR verification (PR #68172)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov created https://github.com/llvm/llvm-project/pull/68172

None

>From 4aec8113bc23d361164f1e164c8e4e36a9eb0ad0 Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov at gmail.com>
Date: Wed, 4 Oct 2023 04:39:11 +0200
Subject: [PATCH] [CLang][Driver] Add new flags to control IR verification

---
 clang/docs/ReleaseNotes.rst           | 6 ++++++
 clang/include/clang/Driver/Options.td | 6 ++++++
 clang/lib/Driver/ToolChains/Clang.cpp | 6 ++++--
 clang/test/Driver/clang_f_opts.c      | 5 +++++
 4 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 3dce7f6a8f9d56e..1e1433589ddd7c9 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -146,6 +146,12 @@ Non-comprehensive list of changes in this release
 
 New Compiler Flags
 ------------------
+* ``-fdisable-llvm-verifier`` and it's complement ``-fno-disable-llvm-verifier``.
+  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
 -------------------------
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 61e0729974c24d1..6911acb7420ec60 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/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 fdisable_llvm_verifier : Flag<["-"], "fdisable-llvm-verifier">,
+  Group<f_clang_Group>, Visibility<[ClangOption, CLOption, DXCOption]>,
+  HelpText<"Disable verification of LLVM IR">, Flags<[NoXarchOption]>;
+def fno_disable_llvm_verifier : Flag<["-"], "fno-disable-llvm-verifier">,
+  Group<f_clang_Group>, Visibility<[ClangOption, CLOption, DXCOption]>,
+  HelpText<"Do not 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]>;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 129adfb9fcc74d1..1f1afee57ba4259 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/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_fdisable_llvm_verifier,
+                   options::OPT_fno_disable_llvm_verifier, !IsAssertBuild)) {
     CmdArgs.push_back("-disable-llvm-verifier");
+  }
 
   // Discard value names in assert builds unless otherwise specified.
   if (Args.hasFlag(options::OPT_fdiscard_value_names,
diff --git a/clang/test/Driver/clang_f_opts.c b/clang/test/Driver/clang_f_opts.c
index 7a3616a2e9f0a48..f9882c2604cbb18 100644
--- a/clang/test/Driver/clang_f_opts.c
+++ b/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 -fdisable-llvm-verifier %s 2>&1 | FileCheck -check-prefix=CHECK-DISABLE-LLVM-VERIFIER %s
+// RUN: %clang -### -S -fno-disable-llvm-verifier %s 2>&1 | FileCheck -check-prefix=CHECK-NO-DISABLE-LLVM-VERIFIER %s
+// CHECK-DISABLE-LLVM-VERIFIER: "-disable-llvm-verifier"
+// CHECK-NO-DISABLE-LLVM-VERIFIER-NOT: "-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"