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.") diff --git a/compiler-rt/test/nsan/fcmp.cpp b/compiler-rt/test/nsan/fcmp.cpp new file mode 100644 index 00000000000000..e9ec84e05221dc --- /dev/null +++ b/compiler-rt/test/nsan/fcmp.cpp @@ -0,0 +1,28 @@ +// RUN: %clangxx_nsan -O2 -g %s -o %t +// RUN: env NSAN_OPTIONS=check_cmp=true,halt_on_error=0 %run %t 2>&1 | FileCheck %s -check-prefix=CMP_ENABLE +// RUN: env NSAN_OPTIONS=check_cmp=false,halt_on_error=0 %run %t 2>&1 | FileCheck %s -check-prefix=CMP_DISABLE + +#include +#include + +// 0.6/0.2 is slightly below 3, so the comparison will fail after a certain +// threshold that depends on the precision of the computation. +__attribute__((noinline)) // To check call stack reporting. +bool DoCmp(double a, double b, double c, double threshold) { + return c - a / b < threshold; + // CMP_ENABLE: WARNING: NumericalStabilitySanitizer: floating-point comparison results depend on precision + // CMP_ENABLE: double {{ *}}precision dec (native): {{.*}}<{{.*}} + // CMP_ENABLE: __float128{{ *}}precision dec (shadow): {{.*}}<{{.*}} + // CMP_ENABLE: {{#0 .*in DoCmp}} +} + +int main() { + double threshold = 1.0; + for (int i = 0; i < 60; ++i) { + threshold /= 2; + // CMP_DISABLE: value at threshold {{.*}} + printf("value at threshold %.20f: %i\n", threshold, + DoCmp(0.6, 0.2, 3.0, threshold)); + } + return 0; +}