[ClangTidy] Add new performance-type-promotion-in-math-fn check.

[jlebar]

Summary

This checks for calls to double-precision math.h with single-precision
arguments. For example, it suggests replacing ::sin(0.f) with
::sinf(0.f).

[Eugene.Zelenko]

Please mention this check in docs/ReleaseNotes.rst (in alphabetical order).

clang-tools-extra/docs/clang-tidy/checks/performance-type-promotion-in-math-fn.rst

6

Please enclose math.h, float and double into ``.

Will be good idea to mention cmath too.

8

Please enclose functions into ``. Same in other places.

9

Please fix double space.

[jlebar]

Formatting fixes in documentation.

clang-tools-extra/docs/clang-tidy/checks/performance-type-promotion-in-math-fn.rst

6

Please enclose math.h, float and double into ``.

Done. I used two backticks, I hope that's the right thing.

Will be good idea to mention cmath too.

What about cmath, exactly?

[Eugene.Zelenko]

clang-tools-extra/docs/clang-tidy/checks/performance-type-promotion-in-math-fn.rst

6

cmath is proper C++ header for math functions prototypes.

[jlebar]

Note that the relevant functions may come from <cmath>.

[alexfh]

Thank you for the new check! A few comments.

clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.cpp

23

const auto * is preferred to avoid duplication of the type name.

63–68

I guess, functions with arbitrary number of parameters can all be handled using forEachArgumentWithParam. Roughly like this:

forEachArgumentWithParam(
   hasType(isBuiltinType(FloatTy)),
   parmVarDecl(hasType(isBuiltinType(DoubleTy)))

One difference to your existing implementation will be that it will match calls where at least one parameter is double and argument is float, not all of them. Do you expect this to make the check more noisy?

146

getLocWithOffset makes the code quite brittle. Imagine whitespace around ::, for example. Same below. In order to make this kind of code more robust, you can operate on tokens (using Lexer).

Same below.

clang-tools-extra/test/clang-tidy/performance-type-promotion-in-math-fn.cpp

71

We usually truncate repeated static parts of CHECK patterns (except for the first one) to make tests a bit less verbose. You can at least truncate the check name in all but the first check pattern.

[jlebar]

Update test, use "auto". Still need to figure out how to lex these function calls properly.

clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.cpp

63–68

Do you expect this to make the check more noisy?

Yes, to the point of not being worth doing, I think.

Specifically, I think there is nothing wrong with calling a two-arg function double function with one float and one double arg and expecting the float arg to be promoted: ::hypot(3.f, 4.) probably *should* call the double version.

So checking that the arg types are all float is important, I think. Checking that the parameter types are all double is less important but also worth doing, I think, so if you declare some bizarre function in the global namespace called e.g. ::hypot, we won't suggest changing that to ::hypotf.

146

Hm. I agree this is super-brittle. But I am having a lot of difficulty using the Lexer successfully.

For one thing, there may be comments basically anywhere in this stream, and I have to skip over them. I see getPreviousNonCommentToken, but it doesn't quite work if I need to go *forward* in the stream. I looked at a bunch of other uses of the Lexer in clang-tidy and they all looked pretty different from what I'm trying to do here, which also suggested that maybe I'm doing the wrong thing.

Is there no way to get the source location of "sin" out of the DeclRefExpr for "::sin"? I don't see it, but it seems bizarre that it wouldn't be there.

Any tips would be much appreciated.

[alexfh]

clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.cpp

63–68

Fair enough. I don't like the verbosity of the code here, but it may really be valuable to be strict here.

146

Skipping from :: to the next identifier should be straightforward using Lexer::getRawToken and Lexer::getLocForEndOfToken. Tell me if you need more details.

[jlebar]

Suggest std::foo instead of ::foof.

I spoke with rtrieu IRL and he suggested I do this to match what he did in
SemaChecking.cpp for calls to "abs". Seems reasonable to me. This also lets
me sidestep the question of lexing the qualifiers, which is nice.

[jlebar]

Thank you very much for the reviews, @alexfh.

[jlebar]

@alexfh , friendly ping. I'm not in a huge rush on this or anything, but I don't want one or both of us to lose all context here...

[alexfh]

LG with one nit.

clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.cpp

146–154

Maybe just make a static StringSet of all the names and check whether the name is in it?

168–169

We definitely should. See the use of IncludeInserter in UnnecessaryValueParamCheck, for example. Fine for a follow-up.

[malcolm.parsons]

In D27284#609937, @Eugene.Zelenko wrote:

Please mention this check in docs/ReleaseNotes.rst (in alphabetical order).

This has not been done.

[jlebar]

In D27284#621052, @malcolm.parsons wrote:

In D27284#609937, @Eugene.Zelenko wrote:

Please mention this check in docs/ReleaseNotes.rst (in alphabetical order).

This has not been done.

Indeed, sorry I missed that. Done now, will be reflected when I submit.

clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.cpp

168–169

OK, would rather send a followup because this patch is already nontrivial. I'll get to work on that -- thank you for the pointer.

[jlebar]

Sent D27748 for #include suggestion.

clang-tools-extra/clang-tidy/performance/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS support)
 
 add_clang_library(clangTidyPerformanceModule
   FasterStringFindCheck.cpp
   ForRangeCopyCheck.cpp
   ImplicitCastInLoopCheck.cpp
   InefficientStringConcatenationCheck.cpp
   PerformanceTidyModule.cpp
+  TypePromotionInMathFnCheck.cpp
   UnnecessaryCopyInitialization.cpp
   UnnecessaryValueParamCheck.cpp
 
   LINK_LIBS
   clangAST
   clangASTMatchers
   clangBasic
   clangLex
   clangTidy
   clangTidyUtils
   )

clang-tools-extra/clang-tidy/performance/PerformanceTidyModule.cpp

 //===--- PeformanceTidyModule.cpp - clang-tidy ----------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "../ClangTidy.h"
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
-#include "InefficientStringConcatenationCheck.h"
-
 #include "FasterStringFindCheck.h"
 #include "ForRangeCopyCheck.h"
 #include "ImplicitCastInLoopCheck.h"
+#include "InefficientStringConcatenationCheck.h"
+#include "TypePromotionInMathFnCheck.h"
 #include "UnnecessaryCopyInitialization.h"
 #include "UnnecessaryValueParamCheck.h"
 
 namespace clang {
 namespace tidy {
 namespace performance {
 
 class PerformanceModule : public ClangTidyModule {
 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
     CheckFactories.registerCheck<FasterStringFindCheck>(
         "performance-faster-string-find");
     CheckFactories.registerCheck<ForRangeCopyCheck>(
         "performance-for-range-copy");
     CheckFactories.registerCheck<ImplicitCastInLoopCheck>(
         "performance-implicit-cast-in-loop");
     CheckFactories.registerCheck<InefficientStringConcatenationCheck>(
         "performance-inefficient-string-concatenation");
+    CheckFactories.registerCheck<TypePromotionInMathFnCheck>(
+        "performance-type-promotion-in-math-fn");
     CheckFactories.registerCheck<UnnecessaryCopyInitialization>(
         "performance-unnecessary-copy-initialization");
     CheckFactories.registerCheck<UnnecessaryValueParamCheck>(
         "performance-unnecessary-value-param");
   }
 };
 
 // Register the PerformanceModule using this statically initialized variable.

clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.h

+//===--- TypePromotionInMathFnCheck.h - clang-tidy---------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_TYPE_PROMOTION_IN_MATH_FN_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_TYPE_PROMOTION_IN_MATH_FN_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace performance {
+
+/// Finds calls to math.h functions with implicit float to double promotions.
+///
+/// For example, warns on ::sin(0.f), because this funciton's parameter is a
+/// double.  You probably meant to call ::sinf(0.f).
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/performance-type-promotion-in-math-fn.html
+class TypePromotionInMathFnCheck : public ClangTidyCheck {
+public:
+  TypePromotionInMathFnCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace performance
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_TYPE_PROMOTION_IN_MATH_FN_H

clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.cpp

+//===--- TypePromotionInMathFnCheck.cpp - clang-tidy-----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "TypePromotionInMathFnCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace performance {
+
+namespace {
+AST_MATCHER_P(Type, isBuiltinType, BuiltinType::Kind, Kind) {
+  if (const BuiltinType *BT = dyn_cast<BuiltinType>(&Node)) {
+    return BT->getKind() == Kind;
+  }
+  return false;
+}
+} // anonymous namespace
+
+void TypePromotionInMathFnCheck::registerMatchers(MatchFinder *Finder) {
+  constexpr BuiltinType::Kind IntTy = BuiltinType::Int;
+  constexpr BuiltinType::Kind LongTy = BuiltinType::Long;
+  constexpr BuiltinType::Kind FloatTy = BuiltinType::Float;
+  constexpr BuiltinType::Kind DoubleTy = BuiltinType::Double;
+  constexpr BuiltinType::Kind LongDoubleTy = BuiltinType::LongDouble;
+
+  auto hasBuiltinTyParam = [](int Pos, BuiltinType::Kind Kind) {
+    return hasParameter(Pos, hasType(isBuiltinType(Kind)));
+  };
+  auto hasBuiltinTyArg = [](int Pos, BuiltinType::Kind Kind) {
+    return hasArgument(Pos, hasType(isBuiltinType(Kind)));
+  };
+
+  // Match calls to foo(double) with a float argument.
+  auto OneDoubleArgFns = hasAnyName(
+      "::acos", "::acosh", "::asin", "::asinh", "::atan", "::atan2", "::atanh",
+      "::cbrt", "::ceil", "::cos", "::cosh", "::erf", "::erfc", "::exp",
+      "::exp2", "::expm1", "::fabs", "::floor", "::ilogb", "::lgamma",
+      "::llrint", "::log", "::log10", "::log1p", "::log2", "::logb", "::lrint",
+      "::modf", "::nearbyint", "::rint", "::round", "::sin", "::sinh", "::sqrt",
+      "::tan", "::tanh", "::tgamma", "::trunc", "::llround", "::lround");
+  Finder->addMatcher(
+      callExpr(callee(functionDecl(OneDoubleArgFns, parameterCountIs(1),
+                                   hasBuiltinTyParam(0, DoubleTy))),
+               hasBuiltinTyArg(0, FloatTy))
+          .bind("call"),
+      this);
+
+  // Match calls to foo(double, double) where both args are floats.
+  auto TwoDoubleArgFns =
+      hasAnyName("::copysign", "::fdim", "::fmax", "::fmin", "::fmod",
+                 "::hypot", "::ldexp", "::nextafter", "::pow", "::remainder");
+  Finder->addMatcher(
+      callExpr(callee(functionDecl(TwoDoubleArgFns, parameterCountIs(2),
+                                   hasBuiltinTyParam(0, DoubleTy),
+                                   hasBuiltinTyParam(1, DoubleTy))),
+               hasBuiltinTyArg(0, FloatTy), hasBuiltinTyArg(1, FloatTy))
+          .bind("call"),
+      this);
+
+  // Match calls to fma(double, double, double) where all args are floats.
+  Finder->addMatcher(
+      callExpr(callee(functionDecl(hasName("::fma"), parameterCountIs(3),
+                                   hasBuiltinTyParam(0, DoubleTy),
+                                   hasBuiltinTyParam(1, DoubleTy),
+                                   hasBuiltinTyParam(2, DoubleTy))),
+               hasBuiltinTyArg(0, FloatTy), hasBuiltinTyArg(1, FloatTy),
+               hasBuiltinTyArg(2, FloatTy))
+          .bind("call"),
+      this);
+
+  // Match calls to frexp(double, int*) where the first arg is a float.
+  Finder->addMatcher(
+      callExpr(callee(functionDecl(
+                   hasName("::frexp"), parameterCountIs(2),
+                   hasBuiltinTyParam(0, DoubleTy),
+                   hasParameter(1, parmVarDecl(hasType(pointerType(
+                                       pointee(isBuiltinType(IntTy)))))))),
+               hasBuiltinTyArg(0, FloatTy))
+          .bind("call"),
+      this);
+
+  // Match calls to nexttoward(double, long double) where the first arg is a
+  // float.
+  Finder->addMatcher(
+      callExpr(callee(functionDecl(hasName("::nexttoward"), parameterCountIs(2),
+                                   hasBuiltinTyParam(0, DoubleTy),
+                                   hasBuiltinTyParam(1, LongDoubleTy))),
+               hasBuiltinTyArg(0, FloatTy))
+          .bind("call"),
+      this);
+
+  // Match calls to remquo(double, double, int*) where the first two args are
+  // floats.
+  Finder->addMatcher(
+      callExpr(
+          callee(functionDecl(
+              hasName("::remquo"), parameterCountIs(3),
+              hasBuiltinTyParam(0, DoubleTy), hasBuiltinTyParam(1, DoubleTy),
+              hasParameter(2, parmVarDecl(hasType(pointerType(
+                                  pointee(isBuiltinType(IntTy)))))))),
+          hasBuiltinTyArg(0, FloatTy), hasBuiltinTyArg(1, FloatTy))
+          .bind("call"),
+      this);
+
+  // Match calls to scalbln(double, long) where the first arg is a float.
+  Finder->addMatcher(
+      callExpr(callee(functionDecl(hasName("::scalbln"), parameterCountIs(2),
+                                   hasBuiltinTyParam(0, DoubleTy),
+                                   hasBuiltinTyParam(1, LongTy))),
+               hasBuiltinTyArg(0, FloatTy))
+          .bind("call"),
+      this);
+
+  // Match calls to scalbn(double, int) where the first arg is a float.
+  Finder->addMatcher(
+      callExpr(callee(functionDecl(hasName("::scalbn"), parameterCountIs(2),
+                                   hasBuiltinTyParam(0, DoubleTy),
+                                   hasBuiltinTyParam(1, IntTy))),
+               hasBuiltinTyArg(0, FloatTy))
+          .bind("call"),
+      this);
+
+  // modf(double, double*) is omitted because the second parameter forces the
+  // type -- there's no conversion from float* to double*.
+}
+
+void TypePromotionInMathFnCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Call = Result.Nodes.getNodeAs<CallExpr>("call");
+  assert(Call != nullptr);
+
+  SourceLocation FnNameStart = Call->getExprLoc();
+  if (auto *D = dyn_cast<DeclRefExpr>(Call->getCallee()->IgnoreImplicit()))
+    if (D->hasQualifier()) {
+      // Skip the "::" following the qualifier.
+      FnNameStart = D->getQualifierLoc().getEndLoc().getLocWithOffset(2);
+    }
+
+  auto FnNameSourceRange = CharSourceRange::getCharRange(
+      FnNameStart, Call->getArg(0)->getExprLoc().getLocWithOffset(-1));
+
+  StringRef FnName = Call->getDirectCallee()->getName();
+  diag(Call->getExprLoc(), "call to '%0' promotes float to double")
+      << FnName << FixItHint::CreateReplacement(
+                       FnNameSourceRange, (llvm::Twine(FnName) + "f").str());
+}
+
+} // namespace performance
+} // namespace tidy
+} // namespace clang

clang-tools-extra/docs/clang-tidy/checks/list.rst

.. toctree::
    modernize-use-transparent-functors
    modernize-use-using
    mpi-buffer-deref
    mpi-type-mismatch
    performance-faster-string-find
    performance-for-range-copy
    performance-implicit-cast-in-loop
    performance-inefficient-string-concatenation
+   performance-type-promotion-in-math-fn
    performance-unnecessary-copy-initialization
    performance-unnecessary-value-param
    readability-avoid-const-params-in-decls
    readability-braces-around-statements
    readability-container-size-empty
    readability-deleted-default
    readability-else-after-return
    readability-function-size

clang-tools-extra/docs/clang-tidy/checks/performance-type-promotion-in-math-fn.rst

+.. title:: clang-tidy - performance-type-promotion-in-math-fn
+
+performance-type-promotion-in-math-fn
+=====================================
+
+Finds calls to math.h functions with implicit float to double promotions.
+
+For example, warns on `::sin(0.f)`, because this funciton's parameter is a
+double.  You probably meant to call `::sinf(0.f)`, or maybe `std::sin(0.f)`.

clang-tools-extra/test/clang-tidy/performance-type-promotion-in-math-fn.cpp

+// RUN: %check_clang_tidy %s performance-type-promotion-in-math-fn %t
+
+double acos(double);
+double acosh(double);
+double asin(double);
+double asinh(double);
+double atan2(double);
+double atan(double);
+double atanh(double);
+double cbrt(double);
+double ceil(double);
+double copysign(double, double);
+double cos(double);
+double cosh(double);
+double erfc(double);
+double erf(double);
+double exp2(double);
+double exp(double);
+double expm1(double);
+double fabs(double);
+double fdim(double, double);
+double floor(double);
+double fma(double, double, double);
+double fmax(double, double);
+double fmin(double, double);
+double fmod(double, double);
+double frexp(double, int *);
+double hypot(double, double);
+double ilogb(double);
+double ldexp(double, double);
+double lgamma(double);
+long long llrint(double);
+double log10(double);
+double log1p(double);
+double log2(double);
+double logb(double);
+double log(double);
+long lrint(double);
+double modf(double);
+double nearbyint(double);
+double nextafter(double, double);
+double nexttoward(double, long double);
+double pow(double, double);
+double remainder(double, double);
+double remquo(double, double, int *);
+double rint(double);
+double round(double);
+double scalbln(double, long);
+double scalbn(double, int);
+double sin(double);
+double sinh(double);
+double sqrt(double);
+double tan(double);
+double tanh(double);
+double tgamma(double);
+double trunc(double);
+long long llround(double);
+long lround(double);
+
+void check_all_fns() {
+  float a, b, c;
+  int i;
+  long l;
+  int *int_ptr;
+
+  acos(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'acos' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  acosf(a);{{$}}
+  acosh(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'acosh' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  acoshf(a);{{$}}
+  asin(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'asin' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  asinf(a);{{$}}
+  asinh(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'asinh' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  asinhf(a);{{$}}
+  atan2(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'atan2' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  atan2f(a);{{$}}
+  atan(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'atan' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  atanf(a);{{$}}
+  atanh(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'atanh' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  atanhf(a);{{$}}
+  cbrt(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'cbrt' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  cbrtf(a);{{$}}
+  ceil(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'ceil' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  ceilf(a);{{$}}
+  copysign(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'copysign' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  copysignf(a, b);{{$}}
+  cos(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'cos' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  cosf(a);{{$}}
+  cosh(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'cosh' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  coshf(a);{{$}}
+  erf(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'erf' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  erff(a);{{$}}
+  erfc(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'erfc' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  erfcf(a);{{$}}
+  exp2(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'exp2' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  exp2f(a);{{$}}
+  exp(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'exp' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  expf(a);{{$}}
+  expm1(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'expm1' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  expm1f(a);{{$}}
+  fabs(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'fabs' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  fabsf(a);{{$}}
+  fdim(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'fdim' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  fdimf(a, b);{{$}}
+  floor(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'floor' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  floorf(a);{{$}}
+  fma(a, b, c);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'fma' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  fmaf(a, b, c);{{$}}
+  fmax(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'fmax' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  fmaxf(a, b);{{$}}
+  fmin(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'fmin' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  fminf(a, b);{{$}}
+  fmod(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'fmod' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  fmodf(a, b);{{$}}
+  frexp(a, int_ptr);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'frexp' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  frexpf(a, int_ptr);{{$}}
+  hypot(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'hypot' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  hypotf(a, b);{{$}}
+  ilogb(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'ilogb' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  ilogbf(a);{{$}}
+  ldexp(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'ldexp' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  ldexpf(a, b);{{$}}
+  lgamma(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'lgamma' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  lgammaf(a);{{$}}
+  llrint(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'llrint' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  llrintf(a);{{$}}
+  llround(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'llround' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  llroundf(a);{{$}}
+  log10(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'log10' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  log10f(a);{{$}}
+  log1p(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'log1p' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  log1pf(a);{{$}}
+  log2(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'log2' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  log2f(a);{{$}}
+  log(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'log' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  logf(a);{{$}}
+  logb(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'logb' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  logbf(a);{{$}}
+  lrint(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'lrint' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  lrintf(a);{{$}}
+  lround(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'lround' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  lroundf(a);{{$}}
+  nearbyint(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'nearbyint' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  nearbyintf(a);{{$}}
+  nextafter(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'nextafter' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  nextafterf(a, b);{{$}}
+  nexttoward(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'nexttoward' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  nexttowardf(a, b);{{$}}
+  pow(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'pow' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  powf(a, b);{{$}}
+  remainder(a, b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'remainder' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  remainderf(a, b);{{$}}
+  remquo(a, b, int_ptr);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'remquo' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  remquof(a, b, int_ptr);{{$}}
+  rint(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'rint' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  rintf(a);{{$}}
+  round(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'round' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  roundf(a);{{$}}
+  scalbln(a, l);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'scalbln' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  scalblnf(a, l);{{$}}
+  scalbn(a, i);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'scalbn' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  scalbnf(a, i);{{$}}
+  sin(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'sin' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  sinf(a);{{$}}
+  sinh(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'sinh' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  sinhf(a);{{$}}
+  sqrt(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'sqrt' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  sqrtf(a);{{$}}
+  tan(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'tan' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  tanf(a);{{$}}
+  tanh(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'tanh' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  tanhf(a);{{$}}
+  tgamma(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'tgamma' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  tgammaf(a);{{$}}
+  trunc(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'trunc' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  truncf(a);{{$}}
+}
+
+// nexttoward/nexttowardf are weird -- the second param is always long double.
+// So we warn if the first arg is a float, regardless of what the second arg is.
+void check_nexttoward() {
+  nexttoward(0.f, 0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'nexttoward' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  nexttowardf(0.f, 0);{{$}}
+  nexttoward(0.f, 0l);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'nexttoward' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  nexttowardf(0.f, 0l);{{$}}
+  nexttoward(0.f, 0.f);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'nexttoward' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  nexttowardf(0.f, 0.f);{{$}}
+  nexttoward(0.f, 0.);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'nexttoward' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  nexttowardf(0.f, 0.);{{$}}
+
+  // No warnings for these.
+  nexttoward(0., 0);
+  nexttoward(0., 0.f);
+  nexttoward(0., 0.);
+}
+
+// The second parameter to scalbn and scalbnf is an int, so we don't care what
+// type you pass as that argument; we warn iff the first argument is a float.
+void check_scalbn() {
+  scalbn(0.f, 0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'scalbn' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  scalbnf(0.f, 0);{{$}}
+  scalbn(0.f, static_cast<char>(0));
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'scalbn' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  scalbnf(0.f, static_cast<char>(0));{{$}}
+
+  // No warnings for these.
+  scalbn(0., 0);
+  scalbn(0., static_cast<char>(0));
+}
+
+// scalbln/scalblnf are like scalbn/scalbnf except their second arg is a long.
+// Again, doesn't matter what we pass for the second arg; we warn iff the first
+// arg is a float.
+void check_scalbln() {
+  scalbln(0.f, 0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'scalbln' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  scalblnf(0.f, 0);{{$}}
+  scalbln(0.f, 0l);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'scalbln' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  scalblnf(0.f, 0l);{{$}}
+
+  // No warnings for these.
+  scalbln(0., 0);
+  scalbln(0., 0l);
+}
+
+// Check that we preserve the leading "::" in our fixit.
+void fixit_preserves_qualifier() {
+  ::sin(0.f);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: call to 'sin' promotes float to double [performance-type-promotion-in-math-fn]
+  // CHECK-FIXES: {{^}}  ::sinf(0.f);{{$}}
+}
+
+float cosf(float);
+double foo(double);         // not a math.h function
+float cos(float);           // not a math.h function (wrong signature)
+double cos(double, double); // not a math.h function (wrong signature)
+
+namespace std {
+void cos(float);
+} // namespace std
+
+void check_no_warnings() {
+  foo(0.); // no warning because not a math.h function.
+
+  sin(0);        // no warning because arg is an int
+  cos(0.);       // no warning because arg is a double
+  std::cos(0.f); // no warning because not ::cos.
+  cosf(0.f);     // no warning; we expect this to take a float
+  cos(0.f);      // does not match the expected signature of ::cos
+  cos(0.f, 0.f); // does not match the expected signature of ::cos
+
+  // No warnings because all args are not floats.
+  remainder(0., 0.f);
+  remainder(0.f, 0.);
+  remainder(0, 0.f);
+  remainder(0.f, 0);
+  fma(0.f, 0.f, 0);
+  fma(0.f, 0.f, 0.);
+  fma(0.f, 0., 0.f);
+  fma(0., 0.f, 0.f);
+}