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Posting to forums is available to community members only. Login or Register |
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Messages |
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prasad_vc
Posts: 0
Online: 
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| 9/20/2006 2:26 AM |
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Hi,
I am trying my hand on DPI, and have an example in which i want to pass a struct as an argument to 'C'. however i am not getting any results.
**********************************
The code is:
// Program to pass struct data-type as an argument.
// Author: Vivek C. Prasad
// Date : 20 september 2006
#include
#include "svdpi.h"
typedef struct {
char a;
int b;
} AB;
AB sc;
int str(const AB sc) {
printf("the byte is: %c\n",sc.a);
printf("the int is: %d\n",sc.b);
return(-1);
}
**********************************
// Program to pass struct data-type as an argument.
// Author: Vivek C. Prasad
// Date : 20 september 2006
module structPass();
int res;
typedef struct packed {
byte a;
shortint b;
} AB;
AB dt_struct;
import "DPI-C" context str = function int structFunction(input dt_struct);
initial begin
dt_struct.a = "V";
dt_struct.b = 10;
res = structFunction(dt_struct);
$display("The struct is passed as an argument.\n");
$display("Byte: %0d\n",dt_struct.a);
$display("Int : %0d\n",dt_struct.b);
$display("Return : %0d\n",res);
end
endmodule
**********************************
The Result is:
the byte is:
the int is: 0
The struct is passed as an argument.
Byte: 86
Int : 10
Return : -1
**********************************
Vivek.
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tpylant
Posts: 87
Online:
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| 9/21/2006 6:28 PM |
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Using example F9.3 in appendix F of the LRM, it looks like the syntax of the str function should be:
int str(const AB *sc) {
printf("the byte is: %c\n", sc->a);
printf("the int is: %d\n", sc->b);
return(-1);
}
Tim |
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tpylant
Posts: 87
Online:
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| 9/21/2006 6:30 PM |
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Also on the SV side, the import should be:
import "DPI-C" context str = function int structFunction(input AB dt_struct);
You were missing the data type for the input argument.
Tim |
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prasad_vc
Posts: 0
Online:
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| 9/21/2006 10:29 PM |
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Hi Tim,
I tried it with the same, but could not get the desired result. Also, when i say "(input AB dt_struct)", the compiler says unsupported data-type in formal argument.
I am using ncsim 5.6s005. Is it the tool issue?
Vivek |
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prasad_vc
Posts: 0
Online:
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| 9/22/2006 7:19 AM |
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Hi Tim,
With the ncsim v5.81 i was able to come up those issues, however one more difficulty has arose, the struct i am passing as an argument, is giving me swapped results. I mean, the struct member 'int' of sv is assigned to struct member 'byte' of 'C' and vice-versa. In my previous output it becomes
the byte is: 10
the int is: 86
The struct is passed as an argument.
Byte: 86
Int : 10
Isn't there anything like packing.low and packing.high as like specman in SystemVerilog.
Vivek.
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tmackett
Posts: 34
Online:
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| 1/23/2007 2:56 PM |
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Hmmmm, the above example came out with some strange characters when I copied/pasted to this. Let me repost:
---file: top.v-------
module top ();
// import functions do a call from SV to C
import "DPI-C" context addone_c= function int addone_sv(input int x);
import "DPI-C" context function void show_vec_inC(input bit [ 31:0] some_vec);
import "DPI-C" context function void show_logic_inC(input logic [ 31:0] some_vec);
typedef struct packed {
int a;
bit [ 9:0] b;
bit [ 5:0] c;
} mydata_struct_s;
import "DPI-C" context function void pass_struct(inout mydata_struct_s t );
bit ⎫:0] some_vec = 32'h12345678;
logic ⎫:0] some_logic = 32'h8765X32Z;
mydata_struct_s mydata_struct_i;
initial
begin
$display("Gimme_Int %d",addone_sv(5));
show_vec_inC(some_vec); // pass reference per SV spec
show_logic_inC(some_logic); // pass reference per SV spec
// stuff the structure with data
mydata_struct_i.a = 9;
mydata_struct_i.b = 10'b10_1011_0110;
mydata_struct_i.c = 6'b11_0101;
pass_struct(mydata_struct_i); // pass reference to packed struct
$display("Verilog a %d", mydata_struct_i.a);
$display("Verilog b %h", mydata_struct_i.b);
$display("Verilog c %h", mydata_struct_i.c);
end
endmodule
-------file: main_task.c----------
#include
#include
// Copyright Cadence Design Systems, Todd Mackett 2007
// This is an example of manipulating packed data structure in SystemVerilog
// Use /tools/inca/include/svdpi.h as a reference
int addone_c(int x) {
return x +1;
}
void show_vec_inC(svBitVecVal* x) {
printf("show_vec_inC\n");
printf("a= %x\n", *x);
}
// svLogicVecVal can have 0,1,X,Z
void show_logic_inC(svLogicVecVal* x) {
printf("show_Logic_inC\n");
printf("a= %x\n", *x);
printf("aval %x\n", x->a);
printf("bval %x\n", x->b);
}
void pass_struct( svBitVecVal* x) { // NOT const so that this can be modified
// can use xΎ] to reference raw array
// printf("Struct = %x, %x\n", x Ύ], x Ώ] );
svBitVecVal aa; // define a local svBitVecVal
// extract field a of SV "struct packed {...} mydata_struct_s
svGetPartselBit(&aa , x, 16, 32);
printf("mydata_struct_s.a: %x \n", aa);
svGetPartselBit(&aa , x, 6, 10);
printf("mydata_struct_s.b: %x \n", aa);
// everything above here works
svGetPartselBit(&aa , x, 0, 6);
printf("mydata_struct_s.c: %x \n", aa);
// svPutBitselBit(aa, 0, sv_0);
printf("AA %x \n", aa);
// do some manipulation on the local svBitVecVal
aa = ~aa; // invert the bits (some generic bit manipulation routine)
// can do something like this too: just set the value of Verilog Structure
// aa = 13;
printf("AA %x \n", aa);
svPutPartselBit(x, aa, 0, 6); // this will modify the Verilog structure
}
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Todd Mackett
Cadence Incisive |
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n_prasanna
Posts: 1
Online:
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| 1/28/2008 12:31 AM |
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| Hi Tim,
I am trying to run the system verilog example you have given here for passing structure as an argument to C function. even with the modifications you had suggested i still do not see the proper values being printed by the C Function.
I am attaching the SV file and the C Function.
System Verilog :-
--------------------------------------
module structPass();
int res;
typedef struct packed {
byte a;
shortint b;
} AB;
AB dt_struct;
import "DPI-C" context str = function int structFunction(input AB dt_struct);
initial begin
dt_struct.a = "V";
dt_struct.b = 10;
res = structFunction(dt_struct);
$display("The struct is passed as an argument.\n");
$display("Byte: %0d\n",dt_struct.a);
$display("Int : %0d\n",dt_struct.b);
$display("Return : %0d\n",res);
end
endmodule
C Function :-
--------------------------------------------
#include
#include "/tools/cadence/install/tools.lnx86/include/svdpi.h"
#include "/tools/cadence/install/tools.lnx86/include/vpi_user.h"
typedef struct {
char a;
int b;
} AB;
AB sc;
int str(const AB *sc) {
printf("the byte is: %c\n",sc->a);
printf("the int is: %d\n",sc->b);
return(-1);
}
---------------------------------------
Any help would be appreciated.
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tpylant
Posts: 87
Online:
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| 1/29/2008 10:31 AM |
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The problem is that the fields are coming across reversed which I don't understand. Here is the code that demonstrates that:
module structPass();
int res;
typedef struct packed {
byte a;
int b;
} AB;
AB dt_struct;
import "DPI-C" context str = function int structFunction(input AB dt_struct);
initial begin
dt_struct.a = "V";
dt_struct.b = 10;
$display("\nThe struct is passed as an argument.");
$display("SV Byte: %0s",dt_struct.a);
$display("SV Int : %0d",dt_struct.b);
res = structFunction(dt_struct);
$display("\nReturn : %0d\n",res);
end
endmodule
#include <stdio.h>
#include "svdpi.h"
typedef struct {
int b;
char a;
} AB;
AB sc;
int str(const AB *sc) {
printf("\nThe struct is received as an argument.\n");
printf("C Byte: %c\n",sc->a);
printf("C Int : %d\n",sc->b);
return(-1);
}
I know Todd posted a way to do it by treating the struct as a vector, but maybe someone else could shed some light on the struct reversing problem.
Tim |
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stephenh
Posts: 77
Online:
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| 1/29/2008 10:38 AM |
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The reversing of the struct is apparently deliberate and universal across all simulators, but I can't remember why it's meant to happen. The fun thing is that packed and unpacked structs behave differently - i.e. one reverses, the other doesn't.
Hopefully one of the simulator gurus can explain.
If I can find the original explanation from a couple of years ago, I'll post that too... |
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Steve H. |
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