[clang] [Clang][Driver] Add new flags to control machine instruction verification (PR #70282)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov updated https://github.com/llvm/llvm-project/pull/70282

>From 9f3711c112159c57becae105561bc988a0caaeb5 Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov at gmail.com>
Date: Thu, 26 Oct 2023 06:07:57 +0200
Subject: [PATCH 1/2] [clang][driver] remove accidentally added NoXarchOption
 flag

This flag was accidentally added in 6da382d27bb5c21dfce8ae5239ab5797bc191cab
Explained in https://github.com/llvm/llvm-project/pull/70282#discussion_r1372537230
---
 clang/include/clang/Driver/Options.td | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index c6b1903a32a0621..f9bf170c32ba25e 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1922,10 +1922,10 @@ defm safe_buffer_usage_suggestions : BoolFOption<"safe-buffer-usage-suggestions"
   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]>;
+  HelpText<"Enable verification of LLVM IR">;
 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]>;
+  HelpText<"Disable verification of LLVM IR">;
 def fdiscard_value_names : Flag<["-"], "fdiscard-value-names">,
   Group<f_clang_Group>, Visibility<[ClangOption, DXCOption]>,
   HelpText<"Discard value names in LLVM IR">, Flags<[NoXarchOption]>;

>From c4b858b791792626e0a5584a0a2aeb877a0151c9 Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov at gmail.com>
Date: Wed, 4 Oct 2023 12:09:15 +0200
Subject: [PATCH 2/2] [Clang][Driver] Add new flags to control machine
 instruction verification

---
 clang/docs/ReleaseNotes.rst           | 7 +++++++
 clang/include/clang/Driver/Options.td | 6 ++++++
 clang/lib/Driver/ToolChains/Clang.cpp | 8 ++++++++
 clang/test/Driver/clang_f_opts.c      | 5 +++++
 4 files changed, 26 insertions(+)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 42f20b9a9bb0410..80cebbe3210983f 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/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
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index f9bf170c32ba25e..092b54967ccdab0 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1926,6 +1926,12 @@ 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">, Flags<[NoXarchOption]>;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 601bbfb927746fc..6b7ae896863e4da 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/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)) {
diff --git a/clang/test/Driver/clang_f_opts.c b/clang/test/Driver/clang_f_opts.c
index ebe8a0520bf0fca..e6bb6f80f00368b 100644
--- a/clang/test/Driver/clang_f_opts.c
+++ b/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"