Add clang warning

Author: MacDue

clang/include/clang/Basic/DiagnosticDriverKinds.td

@@ -502,6 +502,9 @@ def err_sls_hardening_arm_not_supported : Error<
 def warn_drv_large_data_threshold_invalid_code_model: Warning<
   "'%0' only applies to medium and large code models">,
   InGroup<UnusedCommandLineArgument>;
+def warn_drv_math_errno_reenabled_after_veclib: Warning<
+  "math errno re-enabled by '%0' after it was implicitly disabled by '%1',"
+  " this may prevent vectorization with the specified vector library">;
 
 def note_drv_command_failed_diag_msg : Note<
   "diagnostic msg: %0">;

clang/lib/Driver/ToolChains/Clang.cpp

@@ -41,6 +41,7 @@
 #include "clang/Driver/SanitizerArgs.h"
 #include "clang/Driver/Types.h"
 #include "clang/Driver/XRayArgs.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/BinaryFormat/Magic.h"
@@ -2857,6 +2858,10 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
   // List of veclibs which when used with -fveclib imply -fno-math-errno.
   constexpr std::array VecLibImpliesNoMathErrno{llvm::StringLiteral("ArmPL"),
                                                 llvm::StringLiteral("SLEEF")};
+  bool NoMathErrnoWasImpliedByVecLib = false;
+  const Arg *VecLibArg = nullptr;
+  // Track the arg (if any) that reenabled errno after -fveclib for diagnostics.
+  const Arg *ArgThatReenabledMathErrnoAfterVecLib = nullptr;
 
   // Handle various floating point optimization flags, mapping them to the
   // appropriate LLVM code generation flags. This is complicated by several
@@ -2964,6 +2969,12 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
   }
 
   for (const Arg *A : Args) {
+    auto CheckMathErrnoForVecLib =
+        llvm::make_scope_exit([&, MathErrnoBeforeArg = MathErrno] {
+          if (NoMathErrnoWasImpliedByVecLib && !MathErrnoBeforeArg && MathErrno)
+            ArgThatReenabledMathErrnoAfterVecLib = A;
+        });
+
     switch (A->getOption().getID()) {
     // If this isn't an FP option skip the claim below
     default: continue;
@@ -3130,8 +3141,11 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
       FPExceptionBehavior = "strict";
       break;
     case options::OPT_fveclib:
-      if (llvm::is_contained(VecLibImpliesNoMathErrno, A->getValue()))
+      VecLibArg = A;
+      if (llvm::is_contained(VecLibImpliesNoMathErrno, A->getValue())) {
         MathErrno = false;
+        NoMathErrnoWasImpliedByVecLib = true;
+      }
       break;
     case options::OPT_fno_trapping_math:
       if (!TrappingMathPresent && !FPExceptionBehavior.empty() &&
@@ -3346,8 +3360,13 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
   if (ApproxFunc)
     CmdArgs.push_back("-fapprox-func");
 
-  if (MathErrno)
+  if (MathErrno) {
     CmdArgs.push_back("-fmath-errno");
+    if (NoMathErrnoWasImpliedByVecLib)
+      D.Diag(clang::diag::warn_drv_math_errno_reenabled_after_veclib)
+          << ArgThatReenabledMathErrnoAfterVecLib->getAsString(Args)
+          << VecLibArg->getAsString(Args);
+  }
 
  if (AssociativeMath && ReciprocalMath && !SignedZeros && ApproxFunc &&
      !TrappingMath)

clang/test/Driver/fveclib.c

@@ -75,10 +75,22 @@
 // CHECK-ERRNO-ARMPL: "-fveclib=ArmPL"
 // CHECK-ERRNO-ARMPL-NOT: "-fmath-errno"
 
-// RUN: %clang -### --target=aarch64-linux-gnu -fveclib=ArmPL -fmath-errno %s 2>&1 | FileCheck --check-prefix=CHECK-FORCE-ERRNO-ARMPL %s
-// CHECK-FORCE-ERRNO-ARMPL: "-fveclib=ArmPL"
-// CHECK-FORCE-ERRNO-ARMPL-SAME: "-fmath-errno"
-
-// RUN: %clang -### --target=aarch64-linux-gnu -fveclib=SLEEF -fmath-errno %s 2>&1 | FileCheck --check-prefix=CHECK-FORCE-ERRNO-SLEEF %s
-// CHECK-FORCE-ERRNO-SLEEF: "-fveclib=SLEEF"
-// CHECK-FORCE-ERRNO-SLEEF-SAME: "-fmath-errno"
+// RUN: %clang -### --target=aarch64-linux-gnu -fveclib=ArmPL -fmath-errno %s 2>&1 | FileCheck --check-prefix=CHECK-REENABLE-ERRNO-ARMPL %s
+// CHECK-REENABLE-ERRNO-ARMPL: math errno re-enabled by '-fmath-errno' after it was implicitly disabled by '-fveclib=ArmPL', this may prevent vectorization with the specified vector library
+// CHECK-REENABLE-ERRNO-ARMPL: "-fveclib=ArmPL"
+// CHECK-REENABLE-ERRNO-ARMPL-SAME: "-fmath-errno"
+
+// RUN: %clang -### --target=aarch64-linux-gnu -fveclib=SLEEF -fmath-errno %s 2>&1 | FileCheck --check-prefix=CHECK-REENABLE-ERRNO-SLEEF %s
+// CHECK-REENABLE-ERRNO-SLEEF: math errno re-enabled by '-fmath-errno' after it was implicitly disabled by '-fveclib=SLEEF', this may prevent vectorization with the specified vector library
+// CHECK-REENABLE-ERRNO-SLEEF: "-fveclib=SLEEF"
+// CHECK-REENABLE-ERRNO-SLEEF-SAME: "-fmath-errno"
+
+// RUN: %clang -### --target=aarch64-linux-gnu -fveclib=ArmPL -fno-fast-math %s 2>&1 | FileCheck --check-prefix=CHECK-REENABLE-ERRNO-NFM %s
+// CHECK-REENABLE-ERRNO-NFM: math errno re-enabled by '-fno-fast-math' after it was implicitly disabled by '-fveclib=ArmPL', this may prevent vectorization with the specified vector library
+// CHECK-REENABLE-ERRNO-NFM: "-fveclib=ArmPL"
+// CHECK-REENABLE-ERRNO-NFM-SAME: "-fmath-errno"
+
+// RUN: %clang -### --target=aarch64-linux-gnu -fveclib=ArmPL -ffp-model=strict %s 2>&1 | FileCheck --check-prefix=CHECK-REENABLE-ERRNO-FP-MODEL %s
+// CHECK-REENABLE-ERRNO-FP-MODEL: math errno re-enabled by '-ffp-model=strict' after it was implicitly disabled by '-fveclib=ArmPL', this may prevent vectorization with the specified vector library
+// CHECK-REENABLE-ERRNO-FP-MODEL: "-fveclib=ArmPL"
+// CHECK-REENABLE-ERRNO-FP-MODEL-SAME: "-fmath-errno"