[compiler-rt] add check-cmp flag for nsan

[c8ef]

Closes #108435.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: None (c8ef)

Changes

Fixes #108435.

---

Full diff: https://github.com/llvm/llvm-project/pull/108707.diff

2 Files Affected:

• (modified) compiler-rt/lib/nsan/nsan.cpp (+2-2)
• (modified) compiler-rt/lib/nsan/nsan_flags.inc (+4-1)

diff --git a/compiler-rt/lib/nsan/nsan.cpp b/compiler-rt/lib/nsan/nsan.cpp
index 4679bcd589eb45..1c06340549acae 100644
--- a/compiler-rt/lib/nsan/nsan.cpp
+++ b/compiler-rt/lib/nsan/nsan.cpp
@@ -25,7 +25,7 @@
 //          on the runtime configuration. The middle part indicates the type of
 //          the application value, the suffix (f,d,l) indicates the type of the
 //          shadow, and depends on the instrumentation configuration.
-//        * __nsan_fcmp_fail_* emits a warning for an fcmp instruction whose
+//        * __nsan_fcmp_fail_* emits a warning for a fcmp instruction whose
 //          corresponding shadow fcmp result differs.
 //
 //===----------------------------------------------------------------------===//
@@ -682,7 +682,7 @@ void fCmpFailFT(const FT Lhs, const FT Rhs, ShadowFT LhsShadow,
   if (flags().enable_warning_stats)
     nsan_stats->AddWarning(CheckTypeT::kFcmp, pc, bp, 0.0);
 
-  if (flags().disable_warnings)
+  if (flags().disable_warnings || !flags().check_cmp)
     return;
 
   // FIXME: ideally we would print the shadow value as FP128. Right now because
diff --git a/compiler-rt/lib/nsan/nsan_flags.inc b/compiler-rt/lib/nsan/nsan_flags.inc
index 7c9e579d91fc33..760973295a8a50 100644
--- a/compiler-rt/lib/nsan/nsan_flags.inc
+++ b/compiler-rt/lib/nsan/nsan_flags.inc
@@ -49,4 +49,7 @@ NSAN_FLAG(bool, enable_loadtracking_stats, false,
 NSAN_FLAG(bool, poison_in_free, true, "")
 NSAN_FLAG(bool, print_stats_on_exit, false, "If true, print stats on exit.")
 NSAN_FLAG(bool, check_nan, false,
-          "If true, check the floating-point number is nan")
\ No newline at end of file
+          "If true, check the floating-point number is nan")
+NSAN_FLAG(bool, check_cmp, true,
+          "If true, emit a warning for a fcmp instruction whose "
+          "corresponding shadow fcmp result differs.")

[c8ef]

Hi @vitalybuka, could you please take a look at this patch?

[alexander-shaposhnikov]

The patch needs tests

[MaskRay]

Add a test? We typically reserve "fix ..." to mean bug fixes. Implementing a feature can use Close ...

[c8ef]

Add a test? We typically reserve "fix ..." to mean bug fixes. Implementing a feature can use Close ...

Test case added.

[c8ef]

Dear reviewers, could you kindly review this patch again? 🥰
@MaskRay @alexander-shaposhnikov

[c8ef]

Ping. @alexander-shaposhnikov @MaskRay

[alexander-shaposhnikov]

Thanks for the update, I'll come back to this soon

[alexander-shaposhnikov]

LGTM with some minor nits
(the checks in the test need some reorganization, I'll commit it as a follow-up)

[c8ef]

Thanks!