From 4b0cada1baa6ea14bc9d253f0545c24c3f08a422 Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Wed, 13 Jun 2018 17:54:52 +0000 Subject: [PATCH] [CodeGen] make nan builtins pure rather than const (PR37778) https://bugs.llvm.org/show_bug.cgi?id=37778 ...shows a miscompile resulting from marking nan builtins as 'const'. The nan libcalls/builtins take a pointer argument: http://www.cplusplus.com/reference/cmath/nan-function/ ...and the chars dereferenced by that arg are used to fill in the NaN constant payload bits. "const" means that the pointer argument isn't dereferenced. That's translated to "readnone" in LLVM. "pure" means that the pointer argument may be dereferenced. That's translated to "readonly" in LLVM. This change prevents the IR optimizer from killing the lead-up to the nan call here: double a() { char buf[4]; buf[0] = buf[1] = buf[2] = '9'; buf[3] = '\0'; return __builtin_nan(buf); } ...the optimizer isn't currently able to simplify this to a constant as we might hope, but this patch should solve the miscompile. Differential Revision: https://reviews.llvm.org/D48134 git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@334628 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/clang/Basic/Builtins.def | 16 +++++++------- test/CodeGen/math-builtins.c | 36 +++++++++++++++++--------------- 2 files changed, 27 insertions(+), 25 deletions(-) diff --git a/include/clang/Basic/Builtins.def b/include/clang/Basic/Builtins.def index 6f39c16302..dd0730f961 100644 --- a/include/clang/Basic/Builtins.def +++ b/include/clang/Basic/Builtins.def @@ -137,14 +137,14 @@ BUILTIN(__builtin_ldexpl, "LdLdi", "Fne") BUILTIN(__builtin_modf , "ddd*" , "Fn") BUILTIN(__builtin_modff, "fff*" , "Fn") BUILTIN(__builtin_modfl, "LdLdLd*", "Fn") -BUILTIN(__builtin_nan, "dcC*" , "ncF") -BUILTIN(__builtin_nanf, "fcC*" , "ncF") -BUILTIN(__builtin_nanl, "LdcC*", "ncF") -BUILTIN(__builtin_nanf128, "LLdcC*", "ncF") -BUILTIN(__builtin_nans, "dcC*" , "ncF") -BUILTIN(__builtin_nansf, "fcC*" , "ncF") -BUILTIN(__builtin_nansl, "LdcC*", "ncF") -BUILTIN(__builtin_nansf128, "LLdcC*", "ncF") +BUILTIN(__builtin_nan, "dcC*" , "FnU") +BUILTIN(__builtin_nanf, "fcC*" , "FnU") +BUILTIN(__builtin_nanl, "LdcC*", "FnU") +BUILTIN(__builtin_nanf128, "LLdcC*", "FnU") +BUILTIN(__builtin_nans, "dcC*" , "FnU") +BUILTIN(__builtin_nansf, "fcC*" , "FnU") +BUILTIN(__builtin_nansl, "LdcC*", "FnU") +BUILTIN(__builtin_nansf128, "LLdcC*", "FnU") BUILTIN(__builtin_powi , "ddi" , "Fnc") BUILTIN(__builtin_powif, "ffi" , "Fnc") BUILTIN(__builtin_powil, "LdLdi", "Fnc") diff --git a/test/CodeGen/math-builtins.c b/test/CodeGen/math-builtins.c index 4be8981ec3..82f049bdd1 100644 --- a/test/CodeGen/math-builtins.c +++ b/test/CodeGen/math-builtins.c @@ -90,25 +90,25 @@ void foo(double *d, float f, float *fp, long double *l, int *i, const char *c) { __builtin_nan(c); __builtin_nanf(c); __builtin_nanl(c); __builtin_nanf128(c); -// NO__ERRNO: declare double @nan(i8*) [[READNONE]] -// NO__ERRNO: declare float @nanf(i8*) [[READNONE]] -// NO__ERRNO: declare x86_fp80 @nanl(i8*) [[READNONE]] -// NO__ERRNO: declare fp128 @nanf128(i8*) [[READNONE]] -// HAS_ERRNO: declare double @nan(i8*) [[READNONE:#[0-9]+]] -// HAS_ERRNO: declare float @nanf(i8*) [[READNONE]] -// HAS_ERRNO: declare x86_fp80 @nanl(i8*) [[READNONE]] -// HAS_ERRNO: declare fp128 @nanf128(i8*) [[READNONE]] +// NO__ERRNO: declare double @nan(i8*) [[PURE:#[0-9]+]] +// NO__ERRNO: declare float @nanf(i8*) [[PURE]] +// NO__ERRNO: declare x86_fp80 @nanl(i8*) [[PURE]] +// NO__ERRNO: declare fp128 @nanf128(i8*) [[PURE]] +// HAS_ERRNO: declare double @nan(i8*) [[PURE:#[0-9]+]] +// HAS_ERRNO: declare float @nanf(i8*) [[PURE]] +// HAS_ERRNO: declare x86_fp80 @nanl(i8*) [[PURE]] +// HAS_ERRNO: declare fp128 @nanf128(i8*) [[PURE]] __builtin_nans(c); __builtin_nansf(c); __builtin_nansl(c); __builtin_nansf128(c); -// NO__ERRNO: declare double @nans(i8*) [[READNONE]] -// NO__ERRNO: declare float @nansf(i8*) [[READNONE]] -// NO__ERRNO: declare x86_fp80 @nansl(i8*) [[READNONE]] -// NO__ERRNO: declare fp128 @nansf128(i8*) [[READNONE]] -// HAS_ERRNO: declare double @nans(i8*) [[READNONE]] -// HAS_ERRNO: declare float @nansf(i8*) [[READNONE]] -// HAS_ERRNO: declare x86_fp80 @nansl(i8*) [[READNONE]] -// HAS_ERRNO: declare fp128 @nansf128(i8*) [[READNONE]] +// NO__ERRNO: declare double @nans(i8*) [[PURE]] +// NO__ERRNO: declare float @nansf(i8*) [[PURE]] +// NO__ERRNO: declare x86_fp80 @nansl(i8*) [[PURE]] +// NO__ERRNO: declare fp128 @nansf128(i8*) [[PURE]] +// HAS_ERRNO: declare double @nans(i8*) [[PURE]] +// HAS_ERRNO: declare float @nansf(i8*) [[PURE]] +// HAS_ERRNO: declare x86_fp80 @nansl(i8*) [[PURE]] +// HAS_ERRNO: declare fp128 @nansf128(i8*) [[PURE]] __builtin_pow(f,f); __builtin_powf(f,f); __builtin_powl(f,f); @@ -188,7 +188,7 @@ void foo(double *d, float f, float *fp, long double *l, int *i, const char *c) { // NO__ERRNO: declare double @cbrt(double) [[READNONE]] // NO__ERRNO: declare float @cbrtf(float) [[READNONE]] // NO__ERRNO: declare x86_fp80 @cbrtl(x86_fp80) [[READNONE]] -// HAS_ERRNO: declare double @cbrt(double) [[READNONE]] +// HAS_ERRNO: declare double @cbrt(double) [[READNONE:#[0-9]+]] // HAS_ERRNO: declare float @cbrtf(float) [[READNONE]] // HAS_ERRNO: declare x86_fp80 @cbrtl(x86_fp80) [[READNONE]] @@ -581,9 +581,11 @@ void foo(double *d, float f, float *fp, long double *l, int *i, const char *c) { // NO__ERRNO: attributes [[READNONE]] = { {{.*}}readnone{{.*}} } // NO__ERRNO: attributes [[READNONE_INTRINSIC]] = { {{.*}}readnone{{.*}} } // NO__ERRNO: attributes [[NOT_READNONE]] = { nounwind "correctly{{.*}} } +// NO__ERRNO: attributes [[PURE]] = { {{.*}}readonly{{.*}} } // HAS_ERRNO: attributes [[NOT_READNONE]] = { nounwind "correctly{{.*}} } // HAS_ERRNO: attributes [[READNONE_INTRINSIC]] = { {{.*}}readnone{{.*}} } +// HAS_ERRNO: attributes [[PURE]] = { {{.*}}readonly{{.*}} } // HAS_ERRNO: attributes [[READNONE]] = { {{.*}}readnone{{.*}} } // HAS_ERRNO_GNU: attributes [[READNONE_INTRINSIC]] = { {{.*}}readnone{{.*}} } -- 2.50.1