similar to: [LLVMdev] disable insertion of unreachables

What do you mean by "terminating function call"? Is it one with the "noreturn" attribute? if so, the assembly language docs say that program behavior is undefined if such a function ever returns. If your function could possibly return, it needs to not have that attribute. On Sun, Sep 6, 2009 at 4:49 PM, Max Stonebraker<max.stonebraker at gmail.com> wrote: > Hello

> if so, the assembly language docs say that > program behavior is undefined if such a function > ever returns. Yes, that's true, but for some static analysis applications such as control dependence analysis for programs that have arbitrary interprocedural control flow, one needs these additional non-executable control flow edges from noreturn functions to their immediate CFG

On Tue, Sep 8, 2009 at 10:16 PM, Max Stonebraker<max.stonebraker at gmail.com> wrote: > Is there any way to avoid having the unreachables inserted in the first > place? If there's sensible control flow after a function returns, don't mark it or calls to it noreturn. If in fact cannot return, the concept of control flow after the function returns fundamentally makes no sense.

> 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

I am not seeing this happening, at least not for unreachables that follow calls to 'noreturn' functions. On Apr 14, 2014, at 3:48 AM, Anton Korobeynikov <anton at korobeynikov.info> wrote: > Hello > > x86 backend emits ud2 instruction in this case > > On Mon, Apr 14, 2014 at 1:46 PM, Vadim Chugunov <vadimcn at gmail.com> wrote: >> Hi, >> Is it

Hi, Is it somehow possible to have LLVM emit machine code for the 'unreachable' IR instruction, which would assert that it indeed never gets reached? Vadim -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20140414/02108a74/attachment.html>

Hi, When clang/llvm compiles the following sample (with -O2) it optimizes away the second comparison in test1 but not in test2. Is this handling of 'unreachable' by purpose, or is this just a shortcoming of the current optimization passes? GCC and MSVC (with the equivalent code using the __assume intrinsic) both optimize away the comparison in test2. void f1(); void f2(); void

Hi, It looks like PDT.getRootNode() returns NULL for: define fastcc void @c974001__lengthy_calculation. 1736(%struct.FRAME.c974001* nocapture %CHAIN.185) noreturn { entry: br label %bb bb: br label %bb } Isn't it a bug in PostDominatorTree? Please note that this crashes: opt -postdomtree -debug dom_crash.bc I think this should be reported as a bug, -Jakub On Sep 3, 2009, at

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)

Guys, I would like to instrument the bytecode that LLVM produces with assertions. I have written the instrumentation code manually, but I do not know how to halt the program in case the assertion is false. I took a look into the bytecode that LLVM produces for a program like: #include <stdlib.h> int main() { exit(1); } And it is like this: define i32 @main() nounwind { entry:

Victor Campos wrote: > Guys, > > I would like to instrument the bytecode that LLVM produces with > assertions. I have written the instrumentation code manually, but I do > not know how to halt the program in case the assertion is false. I took > a look into the bytecode that LLVM produces for a program like: > > #include <stdlib.h> > int main() { >

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 { entry: %call = call i32

On Oct 24, 2013, at 5:22 AM, Stephan Tolksdorf <st at quanttec.com> wrote: > Hi, > > When clang/llvm compiles the following sample (with -O2) it optimizes away the second comparison in test1 but not in test2. Is this handling of 'unreachable' by purpose, or is this just a shortcoming of the current optimization passes? GCC and MSVC (with the equivalent code using the

Jakub Staszak wrote: > Hi, > > It looks like PDT.getRootNode() returns NULL for: > > define fastcc void @c974001__lengthy_calculation. > 1736(%struct.FRAME.c974001* nocapture %CHAIN.185) noreturn { > entry: > br label %bb > > bb: > br label %bb > } > > > Isn't it a bug in PostDominatorTree? > > Please note that this crashes: >

Hello, I have a minimal testcase which crashes RegisterCoalescer in my out-of-tree target. It only crashes in Debug builds of llc---not in Release builds. Also, interesting to note that the x86 backend lowers this same testcase successfully. I did a quick search of bugs.llvm.org and found no matches. This implies that the problem is in my backend and/or how my backend interacts with

Hi, On 15.04.2014 23:44, Vadim Chugunov wrote: > Hi, > I am curious - how does clang deal with epilogue-less functions that > result from _Raise_Exception being marked 'noreturn'? > I've also been playing with Kai's patch, and discovered that this tends > to greatly confuse Windows stack unwinder in cases when noreturn call is > at the end of a function, so

I have the following C source: extern unsigned int donut; void f1(); void f2(); void f1() { unsigned int *magic = &donut; if (*magic != 286529877) { f2(); } } void f2() { /* Loop here forever if application is built with wrong version of ROM image */ while(1) { ; } } The -O2 level PruneEH pass uses SimplifyFunction() which contains this code: for

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

One of our users recently had a powerfail while connected to our meetme gateway. (Asterisk 1.4.17 on debian 4.0) Through the course of it, asterisk never hung up. His system came back up, and started sending ICMP port unreachables, but the stream went on, flooding him with "silence" media stream packets (there was nobody else in the conference). Is asterisk aware of ICMP

On 01.12.2010 09:25, John McCall wrote: > > One problem I foresee is that it's possible for a dispatch block to become unreachable from its landing pad. If that block is then deleted, we'd lose information about what's supposed to unwind there. This could happen if, e.g., someone had a noreturn destructor. In languages that usefully allow throws from EH destructors (i.e. Ada)