[libc] Enable remaining string functions on the GPU

Summary: We previously had to disable these string functions because they were not compatible with the definitions coming from the GNU / host environment. The GPU, when exporting its declarations, has a very difficult requirement that it be compatible with the host environment as both sides of the compilation need to agree on definitions and what's present. This patch more or less gives up an just copies the definitions as expected by `glibc` if they are provided that way, otherwise we fall back to the accepted way. This is the alternative solution to an existing PR which instead disable's GCC's handling.

Author: jhuber6

clang/lib/Headers/llvm_libc_wrappers/string.h

@@ -13,9 +13,6 @@
 #error "This file is for GPU offloading compilation only"
 #endif
 
-// FIXME: The GNU headers provide C++ standard compliant headers when in C++
-// mode and the LLVM libc does not. We cannot enable memchr, strchr, strchrnul,
-// strpbrk, strrchr, strstr, or strcasestr until this is addressed.
 #include_next <string.h>
 
 #if __has_include(<llvm-libc-decls/string.h>)
@@ -26,8 +23,70 @@
 
 #pragma omp begin declare target
 
+// The GNU headers provide C++ standard compliant headers when in C++ mode and
+// the LLVM libc does not. We need to manually provide the definitions using the
+// same prototypes.
+#if defined(__cplusplus) && defined(__GLIBC__) && \
+ defined(__CORRECT_ISO_CPP_STRING_H_PROTO)
+
+#ifndef __LIBC_ATTRS
+#define __LIBC_ATTRS
+#endif
+
+extern "C" {
+void *memccpy(void *__restrict, const void *__restrict, int,
+ size_t) __LIBC_ATTRS;
+int memcmp(const void *, const void *, size_t) __LIBC_ATTRS;
+void *memcpy(void *__restrict, const void *__restrict, size_t) __LIBC_ATTRS;
+void *memmem(const void *, size_t, const void *, size_t) __LIBC_ATTRS;
+void *memmove(void *, const void *, size_t) __LIBC_ATTRS;
+void *mempcpy(void *__restrict, const void *__restrict, size_t) __LIBC_ATTRS;
+void *memset(void *, int, size_t) __LIBC_ATTRS;
+char *stpcpy(char *__restrict, const char *__restrict) __LIBC_ATTRS;
+char *stpncpy(char *__restrict, const char *__restrict, size_t) __LIBC_ATTRS;
+char *strcat(char *__restrict, const char *__restrict) __LIBC_ATTRS;
+int strcmp(const char *, const char *) __LIBC_ATTRS;
+int strcoll(const char *, const char *) __LIBC_ATTRS;
+char *strcpy(char *__restrict, const char *__restrict) __LIBC_ATTRS;
+size_t strcspn(const char *, const char *) __LIBC_ATTRS;
+char *strdup(const char *) __LIBC_ATTRS;
+size_t strlen(const char *) __LIBC_ATTRS;
+char *strncat(char *, const char *, size_t) __LIBC_ATTRS;
+int strncmp(const char *, const char *, size_t) __LIBC_ATTRS;
+char *strncpy(char *__restrict, const char *__restrict, size_t) __LIBC_ATTRS;
+char *strndup(const char *, size_t) __LIBC_ATTRS;
+size_t strnlen(const char *, size_t) __LIBC_ATTRS;
+size_t strspn(const char *, const char *) __LIBC_ATTRS;
+char *strtok(char *__restrict, const char *) __LIBC_ATTRS;
+char *strtok_r(char *__restrict, const char *__restrict,
+ char **__restrict) __LIBC_ATTRS;
+size_t strxfrm(char *__restrict, const char *__restrict, size_t) __LIBC_ATTRS;
+}
+
+extern "C++" {
+char *strstr(char *, const char *) noexcept __LIBC_ATTRS;
+const char *strstr(const char *, const char *) noexcept __LIBC_ATTRS;
+char *strpbrk(char *, const char *) noexcept __LIBC_ATTRS;
+const char *strpbrk(const char *, const char *) noexcept __LIBC_ATTRS;
+char *strrchr(char *, int) noexcept __LIBC_ATTRS;
+const char *strrchr(const char *, int) noexcept __LIBC_ATTRS;
+char *strchr(char *, int) noexcept __LIBC_ATTRS;
+const char *strchr(const char *, int) noexcept __LIBC_ATTRS;
+char *strchrnul(char *, int) noexcept __LIBC_ATTRS;
+const char *strchrnul(const char *, int) noexcept __LIBC_ATTRS;
+char *strcasestr(char *, const char *) noexcept __LIBC_ATTRS;
+const char *strcasestr(const char *, const char *) noexcept __LIBC_ATTRS;
+void *memrchr(void *__s, int __c, size_t __n) noexcept __LIBC_ATTRS;
+const void *memrchr(const void *__s, int __c, size_t __n) noexcept __LIBC_ATTRS;
+void *memchr(void *__s, int __c, size_t __n) noexcept __LIBC_ATTRS;
+const void *memchr(const void *__s, int __c, size_t __n) noexcept __LIBC_ATTRS;
+}
+
+#else
 #include <llvm-libc-decls/string.h>
 
+#endif
+
 #pragma omp end declare target
 
 #undef __LIBC_ATTRS

libc/config/gpu/entrypoints.txt

@@ -22,32 +22,48 @@ set(TARGET_LIBC_ENTRYPOINTS
 
  # string.h entrypoints
  libc.src.string.bcmp
+ libc.src.string.bcopy
  libc.src.string.bzero
+ libc.src.string.index
  libc.src.string.memccpy
+ libc.src.string.memchr
  libc.src.string.memcmp
  libc.src.string.memcpy
  libc.src.string.memmem
  libc.src.string.memmove
  libc.src.string.mempcpy
+ libc.src.string.memrchr
  libc.src.string.memset
+ libc.src.string.rindex
  libc.src.string.stpcpy
  libc.src.string.stpncpy
  libc.src.string.strcasecmp
+ libc.src.string.strcasestr
  libc.src.string.strcat
+ libc.src.string.strchr
+ libc.src.string.strchrnul
  libc.src.string.strcmp
+ libc.src.string.strcoll
  libc.src.string.strcpy
  libc.src.string.strcspn
+ libc.src.string.strdup
  libc.src.string.strlcat
  libc.src.string.strlcpy
  libc.src.string.strlen
  libc.src.string.strncasecmp
  libc.src.string.strncat
  libc.src.string.strncmp
  libc.src.string.strncpy
+ libc.src.string.strndup
  libc.src.string.strnlen
+ libc.src.string.strpbrk
+ libc.src.string.strrchr
+ libc.src.string.strsep
  libc.src.string.strspn
+ libc.src.string.strstr
  libc.src.string.strtok
  libc.src.string.strtok_r
+ libc.src.string.strxfrm
 
  # stdlib.h entrypoints
  libc.src.stdlib.abs

libc/docs/gpu/support.rst

@@ -45,37 +45,48 @@ string.h
 Function Name Available RPC Required
 ============= ========= ============
 bcmp |check|
+bcopy |check|
 bzero |check|
+index |check|
 memccpy |check|
-memchr 
+memchr |check|
 memcmp |check|
 memcpy |check|
+memmem |check|
 memmove |check|
 mempcpy |check|
-memrchr
+memrchr |check|
 memset |check|
+rindex |check|
 stpcpy |check|
 stpncpy |check|
+strcasecmp |check|
+strcasestr |check|
 strcat |check|
-strchr 
+strchr |check|
+strchrnul |check|
 strcmp |check|
+strcoll |check|
 strcpy |check|
 strcspn |check|
+strdup |check|
 strlcat |check|
 strlcpy |check|
 strlen |check|
+strncasecmp |check|
 strncat |check|
 strncmp |check|
 strncpy |check|
+strndup |check|
 strnlen |check|
-strpbrk 
-strrchr 
+strpbrk |check|
+strrchr |check|
+strsep |check|
 strspn |check|
-strstr 
+strstr |check|
 strtok |check|
 strtok_r |check|
-strdup
-strndup
+strxfrm |check|
 ============= ========= ============
 
 stdlib.h