On Fri, Jun 8, 2012 at 9:13 PM, Jeff Garzik <jeff@xxxxxxxxxx> wrote:
> On 06/08/2012 08:58 AM, Pekka Enberg wrote:
>>
>> This patch attempts to fix code generation for global string access:
>>
>> static char *foo = "Foo !\n";
>>
>> extern int puts(const char *s);
>>
>> int main(int argc, char *argv[])
>> {
>> puts(foo);
>>
>> return 0;
>> }
>>
>> Unfortunately the generated executable SIGSEGVs:
>>
>> [penberg@tux sparse]$ ./sparsec foo.c&& ./a.out
>>
>> Segmentation fault
>>
>> Looking at the IR, Sparse/LLVM generates this:
>>
>> [penberg@tux sparse]$ ./sparse-llvm foo.c | llvm-dis
>> ; ModuleID = '<stdin>'
>>
>> @"<noident>" = private global [7 x i8] c"Foo !\0A\00"
>> @foo = private global [7 x i8]* @"<noident>"
>>
>> define i32 @main(i32, i8**) {
>> L0:
>> %load_target = load i64* bitcast ([7 x i8]* @"<noident>" to i64*)
>> %2 = call i32 @puts(i64 %load_target)
>> ret i32 0
>> }
>>
>> declare i32 @puts(i64)
>>
>> whereas Clang generates the following:
>>
>> @.str = private unnamed_addr constant [7 x i8] c"Foo !\0A\00", align 1
>>
>> define i32 @main(i32 %argc, i8** nocapture %argv) nounwind uwtable {
>> %1 = tail call i32 @puts(i8* getelementptr inbounds ([7 x i8]* @.str,
>> i64 0, i64 0)) nounwind
>> ret i32 0
>> }
>>
>> declare i32 @puts(i8* nocapture) nounwind
>>
>> I'm not sure what the LLVM backend can do here. Sparse linearizes the code
>> to
>> this which is why LLVM backend does the casting:
>>
>> [penberg@tux sparse]$ ./test-linearize foo.c
>> main:
>> .L0x7f341f6f1010:
>> <entry-point>
>> load.64 %r1<- 0[foo]
>> call.32 %r2<- puts, %r1
>> ret.32 $0
>>
>> Comments?
>>
>> Cc: Benjamin Herrenschmidt<benh@xxxxxxxxxxxxxxxxxxx>
>> Cc: Christopher Li<sparse@xxxxxxxxxxx>
>> Cc: Jeff Garzik<jgarzik@xxxxxxxxxx>
>> NOT-Signed-off-by: Pekka Enberg<penberg@xxxxxxxxxx>
>> ---
>> sparse-llvm.c | 8 +++++++-
>> 1 files changed, 7 insertions(+), 1 deletions(-)
>
> ACK
Xi, so I guess your current work on linearize.c might fix the SIGSEGV
I'm seeing?
--
To unsubscribe from this list: send the line "unsubscribe linux-sparse" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
