Pesan vektorizer dan paralelizer
Anda dapat menggunakan opsi /Qpar-report pengompilasi Microsoft C++ dan /Qvec-report untuk mengatur paralelisasi otomatis dan vektorisasi otomatis ke kode alasan output dan pesan informasi tentang aktivitasnya. Artikel ini menjelaskan kode alasan dan pesan.
Pesan informasi
Bergantung pada tingkat pelaporan yang Anda tentukan, salah satu pesan informasi berikut muncul untuk setiap perulangan.
Untuk informasi tentang kode alasan, lihat bagian berikutnya dari artikel ini.
| Pesan informasi | Deskripsi |
|---|---|
| 5001 | Vektor perulangan. |
| 5002 | Perulangan tidak di-vektorisasi karena alasan 'deskripsi'. |
| 5011 | Perulangan diparalelkan. |
| 5012 | Perulangan tidak diparalelkan karena alasan 'deskripsi'. |
| 5021 | Tidak dapat mengaitkan perulangan dengan pragma. |
Bagian berikut mencantumkan kemungkinan kode alasan untuk paralelizer dan vektorizer.
Kode alasan 5xx
Kode alasan 5xx berlaku untuk paralelizer dan vektorizer.
| Kode alasan | Penjelasan |
|---|---|
| 500 | Pesan generik yang mencakup beberapa kasus: Misalnya, perulangan mencakup beberapa keluar, atau header perulangan tidak berakhir dengan menambahkan variabel induksi. |
| 501 | Variabel induksi tidak lokal; atau batas atas tidak invariant perulangan. |
| 502 | Variabel induksi diinjak dengan cara tertentu selain +1 sederhana. |
| 503 | Perulangan mencakup penanganan pengecualian atau pernyataan pengalihan. |
| 504 | Isi perulangan dapat melemparkan pengecualian yang memerlukan penghancuran objek C++. |
| 505 | Perulangan luar memiliki variabel induksi pra-inkrementasi. Keluar dari analisis. |
void code_500(int *A)
{
// Code 500 is emitted if the loop has non-vectorizable flow.
// This can include "if", "break", "continue", the conditional
// operator "?", or function calls.
// It also encompasses correct definition and use of the induction
// variable "i", in that the increment "++i" or "i++" must be the last
// statement in the loop.
int i = 0;
while (i<1000)
{
if (i == 4)
{
break;
}
++i;
A[i] = A[i] + 1;
}
// To resolve code 500, use a 'for' loop with single increment of
// induction variable.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
int bound();
void code_501_example1(int *A)
{
// Code 501 is emitted if the compiler cannot discern the
// induction variable of this loop. In this case, when it checks
// the upper bound of 'i', the compiler cannot prove that the
// function call "bound()" returns the same value each time.
// Also, the compiler cannot prove that the call to "bound()"
// does not modify the values of array A.
for (int i=0; i<bound(); ++i)
{
A[i] = A[i] + 1;
}
// To resolve code 501, ensure that the induction variable is
// a local variable, and ensure that the upper bound is a
// provably loop invariant value.
for (int i=0, imax = bound(); i<imax; ++i)
{
A[i] = A[i] + 1;
}
}
int i;
void code_501_example2(int *A)
{
// Code 501 is emitted if the compiler cannot discern the
// induction variable of this loop. In this case, 'i' is
// a global.
for (i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
// To resolve code 501, ensure that the induction variable is
// a local variable, and ensure that the upper bound is a
// provably loop invariant value.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
void code_502(int *A)
{
// Code 502 is emitted if the compiler cannot discern
// the induction variable of the loop. In this case,
// there are three increments to "i", one of which
// is conditional.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
++i;
if (i < 100)
{
++i;
}
}
// To resolve code 502, ensure that there is just one
// increment of the induction variable, placed in the usual
// spot in the "for" loop.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
void code_503(int *A, int x)
{
// Code 503 is emitted if there are inadmissible
// operations in the loop - for example, exception handling and
// switch statements.
for (int i = 0; i<1000; ++i)
{
switch (x)
{
case 1: A[i] = A[i] + 1;
case 2: A[i] = A[i] + 2;
case 3: A[i] = A[i] + 3;
break;
}
}
// To resolve code 503, try to remove as many switch statements
// and exception handling constructs as possible.
}
// compile with /EHsc
int code_504_helper();
class C504
{
public:
C504();
~C504();
};
void code_504(int *A)
{
// Code 504 is emitted if a C++ object was created and
// that object requires EH unwind tracking information under
// /EHs or /EHsc.
for(int i = 0; i < 1000; ++i)
{
C504 c;
A[i] = code_504_helper();
}
}
void code_505(int *A)
{
// Code 505 is emitted on outer loops with pre-incremented
// induction variables. The vectorizer/parallelizer analysis
// package doesn't support these loops, and they are
// intentionally not converted to post-increment loops to
// prevent a performance degradation.
// To parallelize an outer loop that causes code 505, change
// it to a post-incremented loop.
for (int i=100; i--; )
for (int j=0; j<100; j++) { // this loop is still vectorized
A[j] = A[j] + 1;
}
}
Kode alasan 10xx
Kode alasan 10xx berlaku untuk paralelizer.
| Kode alasan | Penjelasan |
|---|---|
| 1000 | Pengkompilasi mendeteksi dependensi data dalam isi perulangan. |
| 1001 | Kompilator mendeteksi penyimpanan ke variabel skalar dalam isi perulangan, dan skalar tersebut memiliki penggunaan di luar perulangan. |
| 1002 | Kompiler mencoba untuk menyejajarkan perulangan yang memiliki perulangan dalam yang sudah diparalelkan. |
| 1003 | Isi perulangan berisi panggilan intrinsik yang dapat membaca atau menulis ke memori. |
| 1004 | Ada pengurangan skalar dalam tubuh perulangan. Pengurangan skalar dapat terjadi jika perulangan telah di vektorisasi. |
| 1005 | no_parallel Pragma ditentukan. |
| 1006 | Fungsi ini berisi OpenMP. Atasi dengan menghapus OpenMP apa pun dalam fungsi ini. |
| 1007 | Variabel induksi perulangan atau batas perulangan tidak ditandatangani angka 32-bit (int atau long). Atasi dengan mengubah jenis variabel induksi. |
| 1008 | Pengompilasi mendeteksi bahwa perulangan ini tidak melakukan cukup pekerjaan untuk membenarkan paralelisasi otomatis. |
| 1009 | Kompilator mendeteksi upaya untuk menyejajarkan perulangan "do-while". Paralelizer otomatis hanya menargetkan perulangan "for". |
| 1010 | Pengkompilasi mendeteksi bahwa perulangan menggunakan "tidak sama dengan" (!=) untuk kondisinya. |
int A[1000];
void func();
void code_1000()
{
// Code 1000 is emitted if the compiler detects a
// data dependence in the loop body.
// You can resolve this by using the ivdep pragma.
// CAUTION -- the compiler will trust your
// assertion that there are no data dependencies
// in the loop body. If there are, you are generating
// code that may have race conditions.
#pragma loop(hint_parallel(0))
//#pragma loop(ivdep) // ivdep will force this through.
for (int i=0; i<1000; ++i)
{
A[i] = A[i-1] + 1; // data dependence here
func(); // data dependence here
}
}
int code_1001()
{
// Code 1001 is emitted if the compiler detects
// a store to a scalar variable in the loop
// body, and that scalar has a use beyond the loop.
// Resolve this by rewriting your code so
// that the scalar is not needed.
int s = 0;
#pragma loop(hint_parallel(0))
for (int i=0; i<1000; ++i)
{
s = A[i];
}
return s;
}
void code_1002()
{
// Code 1002 is emitted when the compiler tries to
// parallelize a loop that has an inner loop that
// has already been parallelized.
#pragma loop(hint_parallel(0))
for (int i=0; i<1000; ++i) // emit code 1002 for this loop
{
#pragma loop(hint_parallel(0))
for (int j=0; j<1000; ++j) // this loop gets parallelized
{
A[j] = A[j] + 1;
}
}
}
extern "C" void __stosb(unsigned char*, unsigned char, size_t);
void code_1003(unsigned char *dst)
{
// Code 1003 is emitted when the loop body contains an intrinsic
// call that may read or write to memory.
// This can be resolved by using the ivdep pragma.
// CAUTION -- the compiler will trust your
// assertion that there are no data dependencies
// in the loop body. If there are, you are generating
// code that may have race conditions.
#pragma loop(hint_parallel(0))
//#pragma loop(ivdep) // ivdep will force this through.
for (int i=0; i<1000; ++i)
{
__stosb(dst, 'c', 10);
A[i] = A[i] + 1;
}
}
int code_1004()
{
// Code 1004 is emitted when there is a scalar reduction
// in the loop body, which can occur if the loop has been
// vectorized.
// You can resolve this by rewriting your code so that it
// does not have a scalar reduction.
int s = 0;
#pragma loop(hint_parallel(0))
for (int i=0; i<1000; ++i)
{
s += A[i];
}
return s;
}
void code_1005()
{
// Code 1005 is emitted when the
// no_parallel pragma is specified.
#pragma loop(no_parallel)
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
#include <omp.h>
// Compile with /openmp
void code_1006()
{
// Code 1006 is emitted when this function contains
// openmp. Resolve this by removing any openmp in this
// function.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
#pragma omp parallel num_threads(4)
{
int i = omp_get_thread_num();
A[i] = A[i] + 1;
}
}
void code_1007()
{
// Code 1007 is emitted when the loop induction variable
// or the loop bounds are not signed 32-bit numbers (int
// or long). Resolve this by changing the type of the
// induction variable.
#pragma loop(hint_parallel(0))
for (unsigned int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
void code_1008()
{
// Code 1008 is emitted when the compiler detects that
// this loop does not perform enough work to warrant
// auto-parallelization.
// You can resolve this by specifying the hint_parallel
// pragma. CAUTION -- if the loop does not perform
// enough work, parallelizing might cause a potentially
// large performance penalty.
// #pragma loop(hint_parallel(0)) // hint_parallel will force this through
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
void code_1009()
{
// Code 1009 is emitted when the compiler tries to parallelize a
// "do-while" loop. The auto-parallelizer only targets "for" loops.
int i = 0;
#pragma loop(hint_parallel(0))
do
{
A[i] = A[i] + 1;
}
while (++i < 1000);
}
void code_1010()
{
// Code 1010 is emitted when the compiler tries to parallelize a
// loop with a condition code of "!=".
// You can resolve this by replacing it with an ordering comparator
// like "<".
#pragma loop(hint_parallel(0))
for (int i = 0; i != 1000; ++i)
{
A[i]++;
}
}
Kode alasan 11xx
Kode alasan 11xx berlaku untuk vektorizer.
| Kode alasan | Penjelasan |
|---|---|
| 1100 | Perulangan berisi alur kontrol—misalnya, "if" atau "?:". |
| 1101 | Perulangan berisi konversi jenis data (mungkin implisit) yang tidak dapat di-vektorisasi. |
| 1102 | Perulangan berisi operasi non-aritmetika atau non-vektorisasi lainnya. |
| 1103 | Isi perulangan mencakup operasi pergeseran yang ukurannya mungkin bervariasi dalam perulangan. |
| 1104 | Isi perulangan mencakup variabel skalar. |
| 1105 | Perulangan mencakup operasi pengurangan yang tidak dikenal. |
| 1106 | Perulangan luar tidak di-vektorisasi. |
void code_1100(int *A, int x)
{
// Code 1100 is emitted when the compiler detects control flow
// in the loop - for example, "if", the ternary operator "?", and
// the like. Resolve this by flattening or removing control
// flow in the loop body.
// Not all control flow causes 1100; some is indeed
// vectorized.
for (int i=0; i<1000; ++i)
{
// straight line code is more amenable to vectorization
if (x)
{
A[i] = A[i] + 1;
}
}
}
extern "C" int __readcr0();
void code_1102(int *A)
{
// Code 1102 is emitted when the compiler is unable to vectorize
// an operation in the loop body. For example, intrinsics and other
// non-arithmetic, non-logical, and non-memory operations are not
// vectorizable.
// Resolve this by removing as many non-vectorizable operations
// as possible from the loop body.
for (int i=0; i<1000; ++i)
{
A[i] = __readcr0();
}
}
void code_1103(int *A, int *B)
{
// Code 1103 is emitted when the compiler is unable to vectorize
// a "shift" operation. In this example, there are two shifts
// that cannot be vectorized.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] >> B[i]; // not vectorizable
int x = B[i];
A[i] = A[i] >> x; // not vectorizable
}
// To resolve this, ensure that your shift amounts are loop
// invariant. If the shift amounts cannot be loop invariant,
// it may not be possible to vectorize this loop.
int x = B[0];
for (int i=0; i<1000; ++i)
{
A[i] = A[i] >> x; // vectorizable
}
}
int code_1104(int *A, int *B)
{
// When it vectorizes a loop, the compiler must 'expand' scalar
// variables to a vector size such that they can fit in
// vector registers. Code 1104 is emitted when the compiler
// cannot 'expand' such scalars.
// In this example, we try to 'expand' x to be used in the
// vectorized loop. However, there is a use of 'x'
// beyond the loop body, which prohibits this expansion.
// To resolve this, try to limit scalars to be used only in
// the loop body and not beyond, and try to keep their types
// consistent with the loop types.
int x;
for (int i=0; i<1000; ++i)
{
x = B[i];
A[i] = A[i] + x;
}
return x;
}
int code_1105(int *A)
{
// The compiler performs an optimization that's known as "reduction"
// when it operates on each element of an array and computes
// a resulting scalar value - for example, in this piece of code, which
// computes the sum of each element in the array:
int s = 0;
for (int i=0; i<1000; ++i)
{
s += A[i]; // vectorizable
}
// The reduction pattern must resemble the loop in the example. The
// compiler emits code 1105 if it cannot deduce the reduction
// pattern, as shown in this example:
for (int i=0; i<1000; ++i)
{
s += A[i] + s; // code 1105
}
// Similarly, reductions of "float" or "double" types require
// that the /fp:fast switch is thrown. Strictly speaking,
// the reduction optimization that the compiler performs uses
// "floating point reassociation". Reassociation is only
// allowed when /fp:fast is thrown.
return s;
}
void code_1106(int *A)
{
// Code 1106 is emitted when the compiler tries to vectorize
// an outer loop.
for (int i=0; i<1000; ++i) // this loop is not vectorized
{
for (int j=0; j<1000; ++j) // this loop is vectorized
{
A[j] = A[j] + 1;
}
}
}
Kode alasan 12xx
Kode alasan 12xx berlaku untuk vektorizer.
| Kode alasan | Penjelasan |
|---|---|
| 1200 | Perulangan berisi dependensi data yang dibawa perulangan yang mencegah vektorisasi. Perulangan yang berbeda dari perulangan mengganggu satu sama lain sehingga vektorisasi perulangan akan menghasilkan jawaban yang salah, dan vektorizer otomatis tidak dapat membuktikan dirinya bahwa tidak ada dependensi data seperti itu. |
| 1201 | Perubahan dasar array selama perulangan. |
| 1202 | Bidang dalam struktur tidak lebar 32 atau 64 bit. |
| 1203 | Isi perulangan mencakup akses yang tidak bersebelahan ke dalam array. |
| 1204 | Mengkompilasi batas struktur data internal terpukul: terlalu banyak tepi dependensi data. |
void fn();
void code_1200(int *A)
{
// Code 1200 is emitted when data dependence is prohibiting
// vectorization. This can only be resolved by rewriting the
// loop, and considering the marking of loop function calls as
// __forceinline.
for (int i=0; i<1000; ++i)
{
A[i] = A[i-1] + 1; // vectorization-prohibiting
fn(); // vectorization-prohibiting
}
}
void code_1201(int *A)
{
// Code 1201 is emitted when an array base changes
// in the loop body. Resolve this by rewriting your
// code so that varying the array base is not necessary.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
A++;
}
}
struct S_1202
{
short a;
short b;
} s[1000];
short sA[1000], sB[1000], sC[1000];
void code_1202(S_1202 *s)
{
// Code 1202 is emitted when non-vectorizable struct accesses
// are present in the loop body. Only struct accesses
// that are 32 or 64 bits are vectorized.
for (int i=0; i<1000; ++i)
{
s[i].a = s[i].b + 1; // this 16 bit struct access is not vectorizable
sA[i] += sB[i] * sC[i]; // this ensures we don't emit reason code '1300'
}
}
void code_1203(int *A)
{
// Code 1203 is emitted when non-vectorizable memory references
// are present in the loop body. Vectorization of some non-contiguous
// memory access is supported - for example, the gather/scatter pattern.
for (int i=0; i<1000; ++i)
{
A[i] += A[0] + 1; // constant memory access not vectorized
A[i] += A[i*2+2] + 2; // non-contiguous memory access not vectorized
}
}
void code_1204(int *A)
{
// Code 1204 is emitted when internal compiler data structures
// hit a limit on the number of data dependence edges recorded.
// Resolve this by moving the innermost loop to another function.
for (int i=0; i<1000; i++)
for (int j=0; j<1000; j++)
for (int k=0; k<1000; k++)
for (int l=0; l<1000; l++)
{
for (int m=0; m<1000; m++)
A[m] = A[m+i] + A[m+j] + A[m+k] + A[m+l];
}
}
Kode alasan 13xx
Kode alasan 13xx berlaku untuk vektorizer.
| Kode alasan | Penjelasan |
|---|---|
| 1300 | Isi perulangan mengandung sedikit atau tanpa komputasi. |
| 1301 | Loop stride bukan +1. |
| 1302 | Perulangan adalah "do-while". |
| 1303 | Terlalu sedikit perulangan perulangan untuk vektorisasi untuk memberikan nilai. |
| 1304 | Perulangan mencakup penugasan dengan ukuran yang berbeda. |
| 1305 | Informasi jenis tidak cukup. |
void code_1300(int *A, int *B)
{
// Code 1300 is emitted when the compiler detects that there is
// no computation in the loop body.
for (int i=0; i<1000; ++i)
{
A[i] = B[i]; // Do not vectorize, instead emit memcpy
}
}
void code_1301(int *A)
{
// Code 1301 is emitted when the stride of a loop is not positive 1.
// Only loops that have a stride of positive 1 are vectorized;
// rewriting your loop may be required.
for (int i=0; i<1000; i += 2)
{
A[i] = A[i] + 1;
}
}
void code_1302(int *A)
{
// Code 1302 is emitted for "do-while" loops. Only "while"
// and "for" loops are vectorized.
int i = 0;
do
{
A[i] = A[i] + 1;
} while (++i < 1000);
}
int code_1303(int *A, int *B)
{
// Code 1303 is emitted when the compiler detects that
// the number of iterations of the loop is too small to
// make vectorization profitable.
// If the loop computation fits perfectly in
// vector registers - for example, the upper bound is 4, or 8 in
// this case - then the loop _may_ be vectorized.
// This loop is not vectorized because there are 5 iterations
for (int i=0; i<5; ++i)
{
A[i] = A[i] + 1;
}
// This loop is vectorized
for (int i=0; i<4; ++i)
{
A[i] = A[i] + 1;
}
// This loop is not vectorized because runtime pointer checks
// are required to check that A and B don't overlap. It is not
// worth it to vectorize this loop.
for (int i=0; i<4; ++i)
{
A[i] = B[i] + 1;
}
// This loop is not vectorized because of the scalar reduction.
int s = 0;
for (int i=0; i<4; ++i)
{
s += A[i];
}
return s;
}
void code_1304(int *A, short *B)
{
// Code 1304 is emitted when the compiler detects
// different sized statements in the loop body.
// In this case, there is an 32-bit statement and a
// 16-bit statement.
// In cases like this consider splitting the loop into loops to
// maximize vector register utilization.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
B[i] = B[i] + 1;
}
}
typedef struct S_1305
{
int a;
int b;
} S_1305;
void code_1305( S_1305 *s, S_1305 x)
{
// Code 1305 is emitted when the compiler can't discern
// proper vectorizable type information for this loop.
// This includes non-scalar loop types such as struct
// assignments, as in this example.
// Resolve this by ensuring that your loops have statements
// that operate on integers or floating point types.
for (int i=0; i<1000; ++i)
{
s[i] = x;
}
}
Kode alasan 14xx
Kode alasan 14xx terjadi ketika beberapa opsi yang tidak kompatibel dengan vektorisasi ditentukan.
| Kode alasan | Penjelasan |
|---|---|
| 1400 | #pragma loop(no_vector) ditentukan. |
| 1401 | /kernel switch ditentukan saat menargetkan x86 atau ARM. |
| 1402 | /arch:SSE2 atau sakelar yang lebih tinggi tidak ditentukan saat menargetkan x86. |
| 1403 | /arch:ATOM sakelar ditentukan dan perulangan mencakup operasi pada ganda. |
| 1404 | /O1 atau /Os sakelar ditentukan. |
| 1405 | Vektorisasi dinonaktifkan untuk membantu pengoptimalan dynamic-initializer-to-static-initializer. |
void code_1400(int *A)
{
// Code 1400 is emitted when the no_vector pragma
// is specified.
#pragma loop(no_vector)
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
// Compile with /kernel
void code_1401(int *A)
{
// Code 1401 is emitted when /kernel is specified.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
// Compile with /arch:IA32
void code_1402(int *A)
{
// Code 1401 is emitted when /arch:IA32 is specified.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
// Compile with /favor:ATOM
void code_1403(double *A)
{
// Code 1401 is emitted when /favor:ATOM is specified, and
// the loop contains operations on "double" arrays.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
// Compile with /O1 or /Os
void code_1404(int *A)
{
// Code 1401 is emitted when compiling for size.
for (int i=0; i<1000; ++i)
{
A[i] = A[i] + 1;
}
}
Kode alasan 15xx
Kode alasan 15xx berlaku untuk alias. Aliasing terjadi ketika lokasi dalam memori dapat diakses oleh dua nama yang berbeda.
| Kode alasan | Penjelasan |
|---|---|
| 1500 | Kemungkinan alias pada array multi-dimensi. |
| 1501 | Kemungkinan alias pada arrays-of-structs. |
| 1502 | Kemungkinan alias dan indeks array selain n + K. |
| 1503 | Kemungkinan alias dan indeks array memiliki beberapa offset. |
| 1504 | Kemungkinan alias; akan memerlukan terlalu banyak pemeriksaan runtime. |
| 1505 | Kemungkinan alias, tetapi pemeriksaan runtime terlalu kompleks. |
void code_1500(int A[100][100], int B[100][100])
{
// Code 1500 is emitted when runtime pointer
// disambiguation checks are required, and
// there are multidimensional array references.
for (int i=0; i<100; ++i)
{
for (int j=0; j<100; ++j)
{
A[i][j] = B[i][j] + 1;
}
}
}
typedef struct S_1501
{
int a;
int b;
} S_1501;
int iA[1000], iB[1000], iC[1000];
void code_1501(S_1501 *s1, S_1501 *s2)
{
// Code 1501 is emitted when runtime pointer
// disambiguation checks are required, and
// there are array-of-struct accesses in the
// loop body.
for (int i=0; i<100; ++i)
{
s1[i].a = s2[i].b + 1;
iA[i] += iB[i] * iC[i]; // this is to ensure we don't emit reason code '1300'
}
}
void code_1502(int *A, int *B)
{
// Code 1502 is emitted when runtime pointer
// disambiguation checks are required, and
// an array reference has an offset that varies
// in the loop.
int x = 0;
for (int i=0; i<100; ++i)
{
A[i] = B[i + x] + 1;
++x; // 'x' varies in the loop
}
}
void code_1503(int *A, int *B, int x, int y)
{
// Code 1503 is emitted when runtime pointer
// disambiguation checks are required, and
// an array reference has multiple offsets.
for (int i=0; i<100; ++i)
{
A[i] = B[i+x] + B[i+y] + 1; // multiple offsets when addressing 'B': {x, y}
A[i] = B[i+x] + B[i] + 1; // multiple offsets when addressing 'B': {x, 0}
A[i] = B[i+x] + B[i+x] + 1; // this is vectorized
}
}
void code_1504(int *A1, int *A2, int *A3, int *A4,
int *A5, int *A6, int *A7, int *A8,
int *A9, int *A10, int *A11, int *A12,
int *A13, int *A14, int *A15, int *A16)
{
// Code 1504 is emitted when too many runtime
// pointer disambiguation checks are required.
for (int i=0; i<100; ++i)
{
++A1[i];
++A2[i];
++A3[i];
++A4[i];
++A5[i];
++A6[i];
++A7[i];
++A8[i];
++A9[i];
++A10[i];
++A11[i];
++A12[i];
++A13[i];
++A14[i];
++A15[i];
++A16[i];
}
}
void code_1505(int *A, int *B)
{
// Code 1505 is emitted when runtime pointer
// disambiguation checks are required, but are
// too complex for the compiler to discern.
for (int i=0; i<100; ++i)
{
for (int j=0; j<100; ++j)
{
for (int k=0; k<100; ++k)
{
A[i+j-k] = B[i-j+k] * 2;
}
}
}
}
Baca juga
Kesalahan dan peringatan C/C++ Compiler dan build tools
Paralelisasi otomatis dan vektorisasi otomatis
Auto-Vectorizer di Visual Studio 2012 – Gambaran Umum
#pragma loop()
/Q Opsi (Operasi Tingkat Rendah)
/Qpar-report (Tingkat Pelaporan Paralelizer Otomatis)
/Qvec-report (Tingkat Pelaporan Vektorizer Otomatis)
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