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llvm-project/clang/test/CodeGen/libcalls.c
Aaron Ballman 7d644e1215 [C11/C2x] Change the behavior of the implicit function declaration warning 
C89 had a questionable feature where the compiler would implicitly
declare a function that the user called but was never previously
declared. The resulting function would be globally declared as
extern int func(); -- a function without a prototype which accepts zero
or more arguments.

C99 removed support for this questionable feature due to severe
security concerns. However, there was no deprecation period; C89 had
the feature, C99 didn't. So Clang (and GCC) both supported the
functionality as an extension in C99 and later modes.

C2x no longer supports that function signature as it now requires all
functions to have a prototype, and given the known security issues with
the feature, continuing to support it as an extension is not tenable.

This patch changes the diagnostic behavior for the
-Wimplicit-function-declaration warning group depending on the language
mode in effect. We continue to warn by default in C89 mode (due to the
feature being dangerous to use). However, because this feature will not
be supported in C2x mode, we've diagnosed it as being invalid for so
long, the security concerns with the feature, and the trivial
workaround for users (declare the function), we now default the
extension warning to an error in C99-C17 mode. This still gives users
an easy workaround if they are extensively using the extension in those
modes (they can disable the warning or use -Wno-error to downgrade the
error), but the new diagnostic makes it more clear that this feature is
not supported and should be avoided. In C2x mode, we no longer allow an
implicit function to be defined and treat the situation the same as any
other lookup failure.

Differential Revision: https://reviews.llvm.org/D122983
2022-04-20 11:30:12 -04:00

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// RUN: %clang_cc1 -Wno-implicit-function-declaration -fmath-errno -emit-llvm -o - %s -triple i386-unknown-unknown | FileCheck -check-prefix CHECK-YES %s
// RUN: %clang_cc1 -Wno-implicit-function-declaration -emit-llvm -o - %s -triple i386-unknown-unknown | FileCheck -check-prefix CHECK-NO %s
// RUN: %clang_cc1 -Wno-implicit-function-declaration -menable-unsafe-fp-math -emit-llvm -o - %s -triple i386-unknown-unknown | FileCheck -check-prefix CHECK-FAST %s
// CHECK-YES-LABEL: define{{.*}} void @test_sqrt
// CHECK-NO-LABEL: define{{.*}} void @test_sqrt
// CHECK-FAST-LABEL: define{{.*}} void @test_sqrt
void test_sqrt(float a0, double a1, long double a2) {
// CHECK-YES: call float @sqrtf
// CHECK-NO: call float @llvm.sqrt.f32(float
// CHECK-FAST: call reassoc nsz arcp afn float @llvm.sqrt.f32(float
float l0 = sqrtf(a0);
// CHECK-YES: call double @sqrt
// CHECK-NO: call double @llvm.sqrt.f64(double
// CHECK-FAST: call reassoc nsz arcp afn double @llvm.sqrt.f64(double
double l1 = sqrt(a1);
// CHECK-YES: call x86_fp80 @sqrtl
// CHECK-NO: call x86_fp80 @llvm.sqrt.f80(x86_fp80
// CHECK-FAST: call reassoc nsz arcp afn x86_fp80 @llvm.sqrt.f80(x86_fp80
long double l2 = sqrtl(a2);
}
// CHECK-YES: declare float @sqrtf(float noundef)
// CHECK-YES: declare double @sqrt(double noundef)
// CHECK-YES: declare x86_fp80 @sqrtl(x86_fp80 noundef)
// CHECK-NO: declare float @llvm.sqrt.f32(float)
// CHECK-NO: declare double @llvm.sqrt.f64(double)
// CHECK-NO: declare x86_fp80 @llvm.sqrt.f80(x86_fp80)
// CHECK-FAST: declare float @llvm.sqrt.f32(float)
// CHECK-FAST: declare double @llvm.sqrt.f64(double)
// CHECK-FAST: declare x86_fp80 @llvm.sqrt.f80(x86_fp80)
// CHECK-YES-LABEL: define{{.*}} void @test_pow
// CHECK-NO-LABEL: define{{.*}} void @test_pow
void test_pow(float a0, double a1, long double a2) {
// CHECK-YES: call float @powf
// CHECK-NO: call float @llvm.pow.f32
float l0 = powf(a0, a0);
// CHECK-YES: call double @pow
// CHECK-NO: call double @llvm.pow.f64
double l1 = pow(a1, a1);
// CHECK-YES: call x86_fp80 @powl
// CHECK-NO: call x86_fp80 @llvm.pow.f80
long double l2 = powl(a2, a2);
}
// CHECK-YES: declare float @powf(float noundef, float noundef)
// CHECK-YES: declare double @pow(double noundef, double noundef)
// CHECK-YES: declare x86_fp80 @powl(x86_fp80 noundef, x86_fp80 noundef)
// CHECK-NO: declare float @llvm.pow.f32(float, float) [[NUW_RNI:#[0-9]+]]
// CHECK-NO: declare double @llvm.pow.f64(double, double) [[NUW_RNI]]
// CHECK-NO: declare x86_fp80 @llvm.pow.f80(x86_fp80, x86_fp80) [[NUW_RNI]]
// CHECK-YES-LABEL: define{{.*}} void @test_fma
// CHECK-NO-LABEL: define{{.*}} void @test_fma
void test_fma(float a0, double a1, long double a2) {
// CHECK-YES: call float @fmaf
// CHECK-NO: call float @llvm.fma.f32
float l0 = fmaf(a0, a0, a0);
// CHECK-YES: call double @fma
// CHECK-NO: call double @llvm.fma.f64
double l1 = fma(a1, a1, a1);
// CHECK-YES: call x86_fp80 @fmal
// CHECK-NO: call x86_fp80 @llvm.fma.f80
long double l2 = fmal(a2, a2, a2);
}
// CHECK-YES: declare float @fmaf(float noundef, float noundef, float noundef)
// CHECK-YES: declare double @fma(double noundef, double noundef, double noundef)
// CHECK-YES: declare x86_fp80 @fmal(x86_fp80 noundef, x86_fp80 noundef, x86_fp80 noundef)
// CHECK-NO: declare float @llvm.fma.f32(float, float, float) [[NUW_RN2:#[0-9]+]]
// CHECK-NO: declare double @llvm.fma.f64(double, double, double) [[NUW_RN2]]
// CHECK-NO: declare x86_fp80 @llvm.fma.f80(x86_fp80, x86_fp80, x86_fp80) [[NUW_RN2]]
// Just checking to make sure these library functions are marked readnone
void test_builtins(double d, float f, long double ld) {
// CHECK-NO: @test_builtins
// CHECK-YES: @test_builtins
double atan_ = atan(d);
long double atanl_ = atanl(ld);
float atanf_ = atanf(f);
// CHECK-NO: declare double @atan(double noundef) [[NUW_RN:#[0-9]+]]
// CHECK-NO: declare x86_fp80 @atanl(x86_fp80 noundef) [[NUW_RN]]
// CHECK-NO: declare float @atanf(float noundef) [[NUW_RN]]
// CHECK-YES: declare double @atan(double noundef) [[NUW:#[0-9]+]]
// CHECK-YES: declare x86_fp80 @atanl(x86_fp80 noundef) [[NUW]]
// CHECK-YES: declare float @atanf(float noundef) [[NUW]]
double atan2_ = atan2(d, 2);
long double atan2l_ = atan2l(ld, ld);
float atan2f_ = atan2f(f, f);
// CHECK-NO: declare double @atan2(double noundef, double noundef) [[NUW_RN]]
// CHECK-NO: declare x86_fp80 @atan2l(x86_fp80 noundef, x86_fp80 noundef) [[NUW_RN]]
// CHECK-NO: declare float @atan2f(float noundef, float noundef) [[NUW_RN]]
// CHECK-YES: declare double @atan2(double noundef, double noundef) [[NUW]]
// CHECK-YES: declare x86_fp80 @atan2l(x86_fp80 noundef, x86_fp80 noundef) [[NUW]]
// CHECK-YES: declare float @atan2f(float noundef, float noundef) [[NUW]]
double exp_ = exp(d);
long double expl_ = expl(ld);
float expf_ = expf(f);
// CHECK-NO: declare double @llvm.exp.f64(double) [[NUW_RNI]]
// CHECK-NO: declare x86_fp80 @llvm.exp.f80(x86_fp80) [[NUW_RNI]]
// CHECK-NO: declare float @llvm.exp.f32(float) [[NUW_RNI]]
// CHECK-YES: declare double @exp(double noundef) [[NUW]]
// CHECK-YES: declare x86_fp80 @expl(x86_fp80 noundef) [[NUW]]
// CHECK-YES: declare float @expf(float noundef) [[NUW]]
double log_ = log(d);
long double logl_ = logl(ld);
float logf_ = logf(f);
// CHECK-NO: declare double @llvm.log.f64(double) [[NUW_RNI]]
// CHECK-NO: declare x86_fp80 @llvm.log.f80(x86_fp80) [[NUW_RNI]]
// CHECK-NO: declare float @llvm.log.f32(float) [[NUW_RNI]]
// CHECK-YES: declare double @log(double noundef) [[NUW]]
// CHECK-YES: declare x86_fp80 @logl(x86_fp80 noundef) [[NUW]]
// CHECK-YES: declare float @logf(float noundef) [[NUW]]
}
// CHECK-YES: attributes [[NUW]] = { nounwind "frame-pointer"="none" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+cx8,+x87" }
// CHECK-NO-DAG: attributes [[NUW_RN]] = { nounwind readnone{{.*}} }
// CHECK-NO-DAG: attributes [[NUW_RNI]] = { nocallback nofree nosync nounwind readnone speculatable willreturn }
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