search for: noreturn

Hi, Building the following C code I get a call instruction that has no noreturn attribute, while the function itself does have it. void foo(void **b) { __builtin_longjmp(b, 1); } define void @_Z3fooPPv(i8** %b) noreturn nounwind uwtable { entry: %0 = bitcast i8** %b to i8* tail call void @llvm.eh.sjlj.longjmp(i8* %0) <<<<<<<<<<<<&lt...

Hi all, Recently I’ve noticed in coverage profiles that llvm_unreachable and the like are considered uncovered because there’s no special behavior in instrumentation to ‘ignore’ noreturn paths. While I don’t necessarily think it’s ideal to ignore all noreturn decls, I think there’s definitely room for some heuristics around ignoring things like llvm_unreachable (perhaps opt-in?). I’m investigating emitting a zero region for all noreturn decls whilst codegenning, as a start. Anyon...

...use CallInst::hasFnAttr(). It checks for attributes in the instruction and in the function decl. http://llvm.org/docs/doxygen/html/Instructions_8cpp_source.html#l00345 Nuno ----- Original Message ----- > Hi, > > Building the following C code I get a call instruction that has no > noreturn > attribute, while the function itself does have it. > > void foo(void **b) { > __builtin_longjmp(b, 1); > } > > > define void @_Z3fooPPv(i8** %b) noreturn nounwind uwtable { > entry: > %0 = bitcast i8** %b to i8* > tail call void @llvm.eh.sjlj.longjmp(i8* %0) &g...

Dear all, I don't get how llvm handles functions with __attribute__((noreturn)). It seems that LR register is backed up on the stack whilst it will never be used to return from a 'noreturn' function. I have this problem with a home-made backend but it seems that ARM flavour of clang has same behaviour. By the way, SP is also saved, I don't understand why. Is the...

...On Mar 28, 2016, at 1:23 PM, Harlan Haskins via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > Hi all, > > Recently I’ve noticed in coverage profiles that llvm_unreachable and the like are considered uncovered because there’s no special behavior in instrumentation to ‘ignore’ noreturn paths. FWIW, Daniel Dunbar and a few others have brought up the lack of a flexible "suppress coverage" mechanism as a pain-point. There are two separate but related solutions: - We should automatically emit zero mappings for code regions dominated by a call to a noreturn function....

Hi Kostya, On 28/11/12 14:47, Kostya Serebryany wrote: > Hi, > > Building the following C code I get a call instruction that has no noreturn > attribute, while the function itself does have it. > > void foo(void **b) { > __builtin_longjmp(b, 1); > } > > > define void @_Z3fooPPv(i8** %b) noreturn nounwind uwtable { > entry: > %0 = bitcast i8** %b to i8* > tail call void @llvm.eh.sjlj.longjmp(i8*...

Hello, as of gcc v2.7.2.1, the noreturn attribute needs to be given *after* the prototype declaration and not before, but for gcc v3.x, things changed for this attribute again, since gcc v2.5.x did it the way, newer gcc versions prefer it... I've applied a small unified diff, fixing this stuff. THX for listening. CU Tom. (Thomas M...

Hello, I am not sure about the semantic (if any) of returns_twice and noreturn attributes. int fork() __attribute__((returns_twice)); void join(int) __attribute__((noreturn)); int f(int n) { int t = fork(); n++; if (t != 0) join(t); return n; } Produces the following LLVM IR: ; Function Attrs: nounwind uwtable define i32 @f(i32 %n) local_unnamed_addr #0 { entr...

On Fri, Nov 3, 2017 at 5:39 PM, Hal Finkel <hfinkel at anl.gov> wrote: > > On 11/03/2017 07:20 PM, Alexandre Isoard via llvm-dev wrote: > > Hello, > > I am not sure about the semantic (if any) of returns_twice and noreturn > attributes. > > int fork() __attribute__((returns_twice)); > void join(int) __attribute__((noreturn)); > > int f(int n) { > int t = fork(); > n++; > if (t != 0) > join(t); > return n; > } > > Where the n++ has been moved after the if, is that...

I am compiling some code with Clang which needs to jump to a fixed address to perform a "syscall". These fixed addresses contain valid code. I noticed that this code produces a warning: typedef void (*exit_syscall_type) (int status) __attribute__((noreturn)); void _exit(int status) __attribute__ ((noreturn)); void _exit(int status) { ((exit_syscall_type)0x10000)(status); } This (seemingly equivalent) code does not: typedef void (*exit_syscall_type) (int status) __attribute__((noreturn)); void _exit(int status) __attribute__ ((noreturn)); void _ex...

Hi Keir: I spotted some bogus uses of the noreturn keyword on ia64. [IA64]: noreturn cannot be used if function may return The functions die_if_kernel and vmx_die_if_kernel can certainly return. This disqualifies them from using the noreturn keyword which is reserved for functions that never return. Signed-off-by: Herbert Xu <herbert@gondor....

...s: define i32 @main() nounwind { entry: %retval = alloca i32 ; <i32*> [#uses=1] %0 = alloca i32 ; <i32*> [#uses=0] %"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0] call void @exit(i32 1) noreturn nounwind unreachable return: ; No predecessors! %retval1 = load i32* %retval ; <i32> [#uses=1] ret i32 %retval1 } So, what is the LLVM code to insert the call "call void @exit(i32 1) noreturn nounwind"? I thought ab...

...5 deletions(-) diff --git a/builder/index-validate.c b/builder/index-validate.c index d3912f3..33086b2 100644 --- a/builder/index-validate.c +++ b/builder/index-validate.c @@ -38,7 +38,7 @@ extern int do_parse (struct parse_context *context, FILE *in); -static void +static void __attribute__((noreturn)) usage (int exit_status) { printf ("%s index\n", getprogname ()); diff --git a/utils/boot-analysis/boot-analysis.c b/utils/boot-analysis/boot-analysis.c index 04b3bdd..1bec9a5 100644 --- a/utils/boot-analysis/boot-analysis.c +++ b/utils/boot-analysis/boot-analysis.c @@ -88,7 +88,7 @...

...xx_personality_v0(...) declare i32 @llvm.eh.selector(i8*, i8*, ...) nounwind declare void @llvm.eh.resume(i8*, i32) declare void @_ZSt9terminatev() declare i32 @memcmp(i8*, i8*, i64) declare i64 @llvm.expect.i64(i64, i64) nounwind readnone declare void @_ZSt19__throw_logic_errorPKc(i8*) noreturn declare i8* @__cxa_begin_catch(i8*) declare void @__cxa_rethrow() declare void @__cxa_end_catch() declare void @__cxa_call_unexpected(i8*) declare void @_ZdlPv(i8*) nounwind declare void @_ZSt20__throw_length_errorPKc(i8*) noreturn declare void @_ZSt17__throw_bad_allocv() noreturn d...

...m making a llvm compiler for shader-like programs. as we known, shader programs are short and have less function calls. i found that i have to save/restore callee-saved register(CSR) in prolog and epilog. because I can violate ABI from driver(c code) and shader, i plan to append the attribute 'noreturn' to all shader functions. in PrologEpilogInserter.cpp, you can find that it actually honor an attribute 'naked' which avoid saving CSR. however, it also skips generating stack-pointer adjustment, which i need. my patch is as follows. i am targeting RISC processor. can anyone tell me th...

...estion whether we can optimize based on the assumption that stack overflow is undefined behavior. While I think it is according to the C++ standard, Windows Structured Exception Handling and signal handlers might allow programs to recover/exit gracefully. Concretely, the patch D59978 wants add the noreturn attribute to functions that recurse infinitly. Also, a function that unconditionally calls a function with a noreturn attribute can be deduced to be noreturn. Consider the following program: ``` #include <cstdlib> #include <cstdio> void overflow(); // Secret function that triggers a s...

> If there's sensible control flow after a function returns, don't mark > it or calls to it noreturn. How do I prevent llvm-gcc from labelling a particular function with the noreturn attribute so an unreachable is not inserted after a call to it? Does llvm-gcc keep a list of functions somewhere that it thinks do not return? Max On Tue, Sep 8, 2009 at 10:30 PM, Eli Friedman <eli.friedman at g...

When I compile some code with the near-trunk clang++ I get this: ... tail call void @_Unwind_Resume_or_Rethrow(i8* %exn2) noreturn unreachable ... declare void @_Unwind_Resume_or_Rethrow(i8*) ... Same with __cxa_throw. 'noreturn' is missing on declarations. This seems to be a bug. Also can _Unwind_Resume_or_Rethrow actually return? When I run some simple exception code in JIT I see that this function actually ret...

...nd { > entry: > %retval = alloca i32 ; <i32*> [#uses=1] > %0 = alloca i32 ; <i32*> [#uses=0] > %"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0] > call void @exit(i32 1) noreturn nounwind > unreachable > return: ; No predecessors! > %retval1 = load i32* %retval ; <i32> [#uses=1] > ret i32 %retval1 > } > > So, what is the LLVM code to insert the call "call void @exit(i32 1)...

Hi Nadav, > I almost missed your email because you replied only to the list. I understand your argument. I think that my fix addresses a part of it. It says that instructions that do not return should not be removed. > The current implementation of mayReturn is to check the 'noreturn' function attribute. Are you suggesting to add a new attribute that is called 'mustreturn' ? It is as equally difficult to know if a function will halt. a function would only be 'mustreturn' [*] if you can prove that it must return in finite time. By default functions would no...