Re: [GSoC] Elimination of CLooG library installation dependency

Tobias Grosser Fri, 08 Aug 2014 06:16:35 -0700

On 08/08/2014 15:11, Roman Gareev wrote:

I think this is fine. On the other side, I think the test case itself
>is unnecessarily large. I would assume the majority of the code could
>be deleted while still triggering the bug. Could you give it a shot.

I've attached an improved version of the patch.


LGTM.

>Is there anything else you still would like to do?

I wanted to make the current code available to be able to fix all new
possible bugs before 'pencils down'. If I have free time, I'll try to
improve the performance of the generation.


Good, though before let's try to get the correctness right.

>Otherwise, I believe fixing the last remaining bugs is of high importance, as 
we want to enable
>this code as soon as possible to avoid future bitrot.
>
>I understand that reducing this may require some work, but I don't think it
>is that hard. Specifically, you could first compile the individual *.cpp
>files to .o files once using once graphite once not.

I've found out that btCollisionWorld.cpp, btCollisionDispatcher.cpp
and btDiscreteDynamicsWorld.llvm.cpp cause “Segmentation fault”. All
of them produce similar ASTs:

Is this segmentation fault at compile time or at run-time? I believe itwas a segfault at run-time due to a miscompile.

btCollisionWorld.cpp:

CLAST generated by CLooG:

if (8*T_45 >= -T_44+9) {
   for (scat_1=0;scat_1<=T_45-1;scat_1++) {
     if ((8*scat_1+T_44+18446744073709551615)%18446744073709551616 <=
18446744073709551614) {
       (scat_1);
     }
   }
}

isl_codegen:

[P_45, P_44] -> { S_12[i0] -> [0, i0, 0] : exists (e0 = floor((-1 +
P_45)/4294967296), e1 = floor((P_44 + 8i0)/18446744073709551616): i0

>= 0 and 4294967296e0 <= -1 + P_45 and 4294967296e0 >= -4294967296 +

P_45 and 4294967296e0 <= -1 + P_45 - i0 and i0 <= 2147483646 and
18446744073709551616e1 >= -18446744073709551615 + P_44 + 8i0 and
18446744073709551616e1 <= -1 + P_44 + 8i0) }

[P_45, P_44] -> {  : exists (e0 = floor((-1 + P_45)/4294967296):
4294967296e0 <= -1 + P_45 and 4294967296e0 >= -2147483647 + P_45 and
P_45 >= -2147483648 and P_45 <= 2147483647 and P_44 >= 0 and P_44 <=
18446744073709551615) }

[P_45, P_44] -> { [i0, i1, i2] -> separate[o0] }

ISL AST generated by ISL:

for (int c1 = 0; c1 < P_45; c1 += 1)
   if ((P_44 + 8 * c1) % 18446744073709551616 >= 1)
     S_12(c1);

btCollisionDispatcher.cpp:

CLAST generated by CLooG:

if (8*T_81 >= -T_80+9) {
   for (scat_1=0;scat_1<=T_81-1;scat_1++) {
     if ((8*scat_1+T_80+18446744073709551615)%18446744073709551616 <=
18446744073709551614) {
       (scat_1);
     }
   }
}

isl_codegen:

[P_81, P_80] -> { S_22[i0] -> [0, i0, 0] : exists (e0 = floor((-1 +
P_81)/4294967296), e1 = floor((P_80 + 8i0)/18446744073709551616): i0

>= 0 and 4294967296e0 <= -1 + P_81 and 4294967296e0 >= -4294967296 +

P_81 and 4294967296e0 <= -1 + P_81 - i0 and i0 <= 2147483646 and
18446744073709551616e1 >= -18446744073709551615 + P_80 + 8i0 and
18446744073709551616e1 <= -1 + P_80 + 8i0) }

[P_81, P_80] -> {  : exists (e0 = floor((-1 + P_81)/4294967296):
4294967296e0 <= -1 + P_81 and 4294967296e0 >= -2147483647 + P_81 and
P_81 >= -2147483648 and P_81 <= 2147483647 and P_80 >= 0 and P_80 <=
18446744073709551615) }

[P_81, P_80] -> { [i0, i1, i2] -> separate[o0] }

ISL AST generated by ISL:

for (int c1 = 0; c1 < P_81; c1 += 1)
   if ((P_80 + 8 * c1) % 18446744073709551616 >= 1)
     S_22(c1);

btDiscreteDynamicsWorld.llvm.cpp:

CLAST generated by CLooG:

if (8*T_24 >= -T_23+9) {
   for (scat_1=0;scat_1<=T_24-1;scat_1++) {
     if ((8*scat_1+T_23+18446744073709551615)%18446744073709551616 <=
18446744073709551614) {
       (scat_1);
     }
   }
}

isl_codegen:

[P_24, P_23] -> { S_13[i0] -> [0, i0, 0] : exists (e0 = floor((-1 +
P_24)/4294967296), e1 = floor((P_23 + 8i0)/18446744073709551616): i0

>= 0 and 4294967296e0 <= -1 + P_24 and 4294967296e0 >= -4294967296 +

P_24 and 4294967296e0 <= -1 + P_24 - i0 and i0 <= 2147483646 and
18446744073709551616e1 >= -18446744073709551615 + P_23 + 8i0 and
18446744073709551616e1 <= -1 + P_23 + 8i0) }

[P_24, P_23] -> {  : exists (e0 = floor((-1 + P_24)/4294967296):
4294967296e0 <= -1 + P_24 and 4294967296e0 >= -2147483647 + P_24 and
P_24 >= -2147483648 and P_24 <= 2147483647 and P_23 >= 0 and P_23 <=
18446744073709551615) }

[P_24, P_23] -> { [i0, i1, i2] -> separate[o0] }

ISL AST generated by ISL:

for (int c1 = 0; c1 < P_24; c1 += 1)
   if ((P_23 + 8 * c1) % 18446744073709551616 >= 1)
     S_13(c1);

CLAST generated by CLooG:

if (8*T_46 >= -T_45+9) {
   for (scat_1=0;scat_1<=T_46-1;scat_1++) {
     if ((8*scat_1+T_45+18446744073709551615)%18446744073709551616 <=
18446744073709551614) {
       (scat_1);
     }
   }
}

isl_codegen:

[P_46, P_45] -> { S_16[i0] -> [0, i0, 0] : exists (e0 = floor((-1 +
P_46)/4294967296), e1 = floor((P_45 + 8i0)/18446744073709551616): i0

>= 0 and 4294967296e0 <= -1 + P_46 and 4294967296e0 >= -4294967296 +

P_46 and 4294967296e0 <= -1 + P_46 - i0 and i0 <= 2147483646 and
18446744073709551616e1 >= -18446744073709551615 + P_45 + 8i0 and
18446744073709551616e1 <= -1 + P_45 + 8i0) }

[P_46, P_45] -> {  : exists (e0 = floor((-1 + P_46)/4294967296):
4294967296e0 <= -1 + P_46 and 4294967296e0 >= -2147483647 + P_46 and
P_46 >= -2147483648 and P_46 <= 2147483647 and P_45 >= 0 and P_45 <=
18446744073709551615) }

[P_46, P_45] -> { [i0, i1, i2] -> separate[o0] }

ISL AST generated by ISL:

for (int c1 = 0; c1 < P_46; c1 += 1)
   if ((P_45 + 8 * c1) % 18446744073709551616 >= 1)
     S_16(c1);

CLAST generated by CLooG:

if (8*T_18 >= -T_17+9) {
   for (scat_1=0;scat_1<=T_18-1;scat_1++) {
     if ((8*scat_1+T_17+18446744073709551615)%18446744073709551616 <=
18446744073709551614) {
       (scat_1);
     }
   }
}

isl_codegen:

[P_18, P_17] -> { S_12[i0] -> [0, i0, 0] : exists (e0 = floor((-1 +
P_18)/4294967296), e1 = floor((P_17 + 8i0)/18446744073709551616): i0

>= 0 and 4294967296e0 <= -1 + P_18 and 4294967296e0 >= -4294967296 +

P_18 and 4294967296e0 <= -1 + P_18 - i0 and i0 <= 2147483646 and
18446744073709551616e1 >= -18446744073709551615 + P_17 + 8i0 and
18446744073709551616e1 <= -1 + P_17 + 8i0) }

[P_18, P_17] -> {  : exists (e0 = floor((-1 + P_18)/4294967296):
4294967296e0 <= -1 + P_18 and 4294967296e0 >= -2147483647 + P_18 and
P_18 >= -2147483648 and P_18 <= 2147483647 and P_17 >= 0 and P_17 <=
18446744073709551615) }

[P_18, P_17] -> { [i0, i1, i2] -> separate[o0] }

ISL AST generated by ISL:

for (int c1 = 0; c1 < P_18; c1 += 1)
   if ((P_17 + 8 * c1) % 18446744073709551616 >= 1)
     S_12(c1);

I think that, for example, the following code

if (8*T_45 >= -T_44+9) {
   for (scat_1=0;scat_1<=T_45-1;scat_1++) {
     if ((8*scat_1+T_44+18446744073709551615)%18446744073709551616 <=
18446744073709551614) {
       (scat_1);
     }
   }
}

is equivalent to

if (8*T_45 >= -T_44+9) {
   for (scat_1=0;scat_1<=T_45-1;scat_1++) {
     if ((8*scat_1+T_44)%18446744073709551616 <= -1) {
       (scat_1);
     }
   }
}

If I'm not mistaken it's not equivalent to

for (int c1 = 0; c1 < P_45; c1 += 1)
   if ((P_44 + 8 * c1) % 18446744073709551616 >= 1)
     S_12(c1);

Maybe the ISL generator generates wrong code. What do you think about this?

Possibly. Can you split the .cpp files such that you only compile asingle function with graphite and that compiling this function causesthe miscompile. This allows us to look at less code.


Cheers,
Tobias

Re: [GSoC] Elimination of CLooG library installation dependency

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