1// RUN: %libomptarget-compilexx-run-and-check-generic
2
3// Assuming the stack is allocated on the host starting at high addresses, the
4// host memory layout for the following program looks like this:
5//
6// low addr <----------------------------------------------------- high addr
7// | 16 bytes | 16 bytes | 16 bytes | ? bytes |
8// | collidePost | s | collidePre | stackPad |
9// | | x | y | z | | |
10// `-------------'
11// ^ `--------'
12// | ^
13// | |
14// | `-- too much padding (< 16 bytes) for s maps here
15// |
16// `------------------array extension error maps here
17//
18// libomptarget used to add too much padding to the device allocation of s and
19// map it back to the host at the location indicated above when all of the
20// following conditions were true:
21// - Multiple members (s.y and s.z below) were mapped. In this case, initial
22// padding might be needed to ensure later mapped members (s.z) are aligned
23// properly on the device. (If the first member in the struct, s.x, were also
24// mapped, then the correct initial padding would always be zero.)
25// - mod16 = &s % 16 was not a power of 2 (e.g., 0x7ffcce2b584e % 16 = 14).
26// libomptarget then incorrectly assumed mod16 was the existing host memory
27// alignment of s. (The fix was to only look for alignments that are powers
28// of 2.)
29// - &s.y % mod16 was > 1 (e.g., 0x7ffcce2b584f % 14 = 11). libomptarget added
30// padding of that size for s, but at most 1 byte is ever actually needed.
31//
32// Below, we try many sizes of stackPad to try to produce those conditions.
33//
34// When collidePost was then mapped to the same host memory as the unnecessary
35// padding for s, libomptarget reported an array extension error. collidePost
36// is never fully contained within that padding (which would avoid the extension
37// error) because collidePost is 16 bytes while the padding is always less than
38// 16 bytes due to the modulo operations. (Later, libomptarget was changed not
39// to consider padding to be mapped to the host, so it cannot be involved in
40// array extension errors.)
41
42#include <stdint.h>
43#include <stdio.h>
44
45template <typename StackPad>
46void test() {
47 StackPad stackPad;
48 struct S { char x; char y[7]; char z[8]; };
49 struct S collidePre, s, collidePost;
50 uintptr_t mod16 = (uintptr_t)&s % 16;
51 fprintf(stderr, "&s = %p\n", &s);
52 fprintf(stderr, format: "&s %% 16 = %lu\n", mod16);
53 if (mod16) {
54 fprintf(stderr, "&s.y = %p\n", &s.y);
55 fprintf(stderr, format: "&s.y %% %lu = %lu\n", mod16, (uintptr_t)&s.y % mod16);
56 }
57 fprintf(stderr, "&collidePre = %p\n", &collidePre);
58 fprintf(stderr, "&collidePost = %p\n", &collidePost);
59 #pragma omp target data map(to:s.y, s.z)
60 #pragma omp target data map(to:collidePre, collidePost)
61 ;
62}
63
64#define TEST(StackPad) \
65 fprintf(stderr, "-------------------------------------\n"); \
66 fprintf(stderr, "StackPad=%s\n", #StackPad); \
67 test<StackPad>()
68
69int main() {
70 TEST(char[1]);
71 TEST(char[2]);
72 TEST(char[3]);
73 TEST(char[4]);
74 TEST(char[5]);
75 TEST(char[6]);
76 TEST(char[7]);
77 TEST(char[8]);
78 TEST(char[9]);
79 TEST(char[10]);
80 TEST(char[11]);
81 TEST(char[12]);
82 TEST(char[13]);
83 TEST(char[14]);
84 TEST(char[15]);
85 TEST(char[16]);
86 // CHECK: pass
87 printf(format: "pass\n");
88 return 0;
89}
90

source code of offload/test/mapping/power_of_two_alignment.cpp