Partial revert of 183015

[eugenis]

Summary

Re-enable several builtins in non-gnu modes.
Fixes PR16138.

[rsmith]

Looks OK as a short-term fix for the ones with the "j" flag. Do we really need to do this for the "fn" ones?

[eugenis]

You mean "fr". Not necessary, I guess. Missing (noreturn) attribute can not do much harm.

[eugenis]

Reverted changes for "pr" builtins.
The only ones that are re-enabled now are "j" - i.e., returns_twice.
PTAL

[rsmith]

LGTM

[rsmith]

include/clang/Basic/Builtins.def

740–743

Please update this comment to explain why we don't have ALL_GNU_LANGUAGES for those builtins with the 'j' flag.

[eugenis]

include/clang/Basic/Builtins.def

740–743

done

[eugenis]

Committed in r206362.

include/clang/Basic/Builtins.def

 LIBBUILTIN(vscanf, "icC*Ra",      "fS:0:", "stdio.h", ALL_LANGUAGES)
 LIBBUILTIN(vfscanf, "iP*RcC*Ra",  "fS:1:", "stdio.h", ALL_LANGUAGES)
 LIBBUILTIN(vsscanf, "icC*RcC*Ra", "fS:1:", "stdio.h", ALL_LANGUAGES)
 // C99
 #undef setjmp
 LIBBUILTIN(setjmp, "iJ",          "fj",    "setjmp.h", ALL_LANGUAGES)
 LIBBUILTIN(longjmp, "vJi",        "fr",    "setjmp.h", ALL_LANGUAGES)
 
 // Non-C library functions, active in GNU mode only.
+// Functions with (returns_twice) attribute (marked as "j") are still active in
+// all languages, because losing this attribute would result in miscompilation
+// when these functions are used in non-GNU mode. PR16138.
 LIBBUILTIN(alloca, "v*z",         "f",     "stdlib.h", ALL_GNU_LANGUAGES)
 // POSIX string.h
 LIBBUILTIN(stpcpy, "c*c*cC*",     "f",     "string.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(stpncpy, "c*c*cC*z",   "f",     "string.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(strdup, "c*cC*",       "f",     "string.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(strndup, "c*cC*z",     "f",     "string.h", ALL_GNU_LANGUAGES)
 // POSIX strings.h
 LIBBUILTIN(index, "c*cC*i",       "f",     "strings.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(rindex, "c*cC*i",      "f",     "strings.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(bzero, "vv*z",         "f",     "strings.h", ALL_GNU_LANGUAGES)
 // In some systems str[n]casejmp is a macro that expands to _str[n]icmp.
 // We undefine then here to avoid wrong name.
 #undef strcasecmp
 #undef strncasecmp
 LIBBUILTIN(strcasecmp, "icC*cC*", "f",     "strings.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(strncasecmp, "icC*cC*z", "f",   "strings.h", ALL_GNU_LANGUAGES)
 // POSIX unistd.h
 LIBBUILTIN(_exit, "vi",           "fr",    "unistd.h", ALL_GNU_LANGUAGES)
-LIBBUILTIN(vfork, "p",            "fj",    "unistd.h", ALL_GNU_LANGUAGES)
+LIBBUILTIN(vfork, "p",            "fj",    "unistd.h", ALL_LANGUAGES)
 // POSIX setjmp.h
 
 // In some systems setjmp is a macro that expands to _setjmp. We undefine
 // it here to avoid having two identical LIBBUILTIN entries.
-LIBBUILTIN(_setjmp, "iJ",         "fj",   "setjmp.h", ALL_GNU_LANGUAGES)
-LIBBUILTIN(__sigsetjmp, "iSJi",   "fj",   "setjmp.h", ALL_GNU_LANGUAGES)
-LIBBUILTIN(sigsetjmp, "iSJi",     "fj",   "setjmp.h", ALL_GNU_LANGUAGES)
-LIBBUILTIN(setjmp_syscall, "iJ",  "fj",   "setjmp.h", ALL_GNU_LANGUAGES)
-LIBBUILTIN(savectx, "iJ",         "fj",   "setjmp.h", ALL_GNU_LANGUAGES)
-LIBBUILTIN(qsetjmp, "iJ",         "fj",   "setjmp.h", ALL_GNU_LANGUAGES)
-LIBBUILTIN(getcontext, "iK*",     "fj",   "setjmp.h", ALL_GNU_LANGUAGES)
+LIBBUILTIN(_setjmp, "iJ",         "fj",   "setjmp.h", ALL_LANGUAGES)
+LIBBUILTIN(__sigsetjmp, "iSJi",   "fj",   "setjmp.h", ALL_LANGUAGES)
+LIBBUILTIN(sigsetjmp, "iSJi",     "fj",   "setjmp.h", ALL_LANGUAGES)
+LIBBUILTIN(setjmp_syscall, "iJ",  "fj",   "setjmp.h", ALL_LANGUAGES)
+LIBBUILTIN(savectx, "iJ",         "fj",   "setjmp.h", ALL_LANGUAGES)
+LIBBUILTIN(qsetjmp, "iJ",         "fj",   "setjmp.h", ALL_LANGUAGES)
+LIBBUILTIN(getcontext, "iK*",     "fj",   "setjmp.h", ALL_LANGUAGES)
 
 LIBBUILTIN(_longjmp, "vJi",       "fr",    "setjmp.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(siglongjmp, "vSJi",    "fr",    "setjmp.h", ALL_GNU_LANGUAGES)
 // non-standard but very common
 LIBBUILTIN(strlcpy, "zc*cC*z",    "f",     "string.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(strlcat, "zc*cC*z",    "f",     "string.h", ALL_GNU_LANGUAGES)
 //   id objc_msgSend(id, SEL, ...)
 LIBBUILTIN(objc_msgSend, "GGH.",   "f",     "objc/message.h", OBJC_LANG)

test/CodeGen/function-attributes.c

 // RUN: %clang_cc1 -triple i386-unknown-unknown -emit-llvm -Os -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple i386-unknown-unknown -emit-llvm -Os -std=c99 -o - %s | FileCheck %s
 // CHECK: define signext i8 @f0(i32 %x) [[NUW:#[0-9]+]]
 // CHECK: define zeroext i8 @f1(i32 %x) [[NUW]]
 // CHECK: define void @f2(i8 signext %x) [[NUW]]
 // CHECK: define void @f3(i8 zeroext %x) [[NUW]]
 // CHECK: define signext i16 @f4(i32 %x) [[NUW]]
 // CHECK: define zeroext i16 @f5(i32 %x) [[NUW]]
 // CHECK: define void @f6(i16 signext %x) [[NUW]]
 // CHECK: define void @f7(i16 zeroext %x) [[NUW]]

 // CHECK: [[RT_CALL]]
 // CHECK: ret void
 typedef int jmp_buf[((9 * 2) + 3 + 16)];
 int setjmp(jmp_buf);
 void f19(void) {
   setjmp(0);
 }
 
+// CHECK-LABEL: define void @f20()
+// CHECK: {
+// CHECK: call i32 @_setjmp(i32* null)
+// CHECK: [[RT_CALL]]
+// CHECK: ret void
+int _setjmp(jmp_buf);
+void f20(void) {
+  _setjmp(0);
+}
+
 // CHECK: attributes [[NUW]] = { nounwind optsize readnone{{.*}} }
 // CHECK: attributes [[AI]] = { alwaysinline nounwind optsize readnone{{.*}} }
 // CHECK: attributes [[ALIGN]] = { nounwind optsize readnone alignstack=16{{.*}} }
 // CHECK: attributes [[RT]] = { nounwind optsize returns_twice{{.*}} }
 // CHECK: attributes [[NR]] = { noreturn nounwind optsize }
 // CHECK: attributes [[NUW_RN]] = { nounwind optsize readnone }
 // CHECK: attributes [[RT_CALL]] = { nounwind optsize returns_twice }

test/Sema/builtins-gnu-mode.c

 // RUN: %clang_cc1 -fsyntax-only -verify -std=c99 %s
 // PR16138
 // expected-no-diagnostics
 
 int alloca;
 int stpcpy;
 int stpncpy;
 int strdup;
 int strndup;
 int index;
 int rindex;
 int bzero;
 int strcasecmp;
 int strncasecmp;
 int _exit;
-int vfork;
-int _setjmp;
-int __sigsetjmp;
-int sigsetjmp;
-int setjmp_syscall;
-int savectx;
-int qsetjmp;
-int getcontext;
 int _longjmp;
 int siglongjmp;
 int strlcpy;
 int strlcat;