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
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