| Age | Commit message (Collapse) | Author |
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A proposed fix for the issue #95611, [OpenMP][SIMD] ordered has no
effect in a loop SIMD region as of LLVM 18.1.0
Changes:
- Implement new lowering behavior: Conservatively serialize "omp simd"
loops that have `omp simd ordered` directive to prevent incorrect
vectorization (which results in incorrect execution behavior of the
miscompiled program).
Implementation outline:
- We start with the optimistic default initial value of
`LoopStack.setParallel(/Enable=/true);` in
`CodeGenFunction::EmitOMPSimdInit(const OMPLoopDirective &D)`.
- We only disable the loop parallel memory access assumption with `if
(HasOrderedDirective) LoopStack.setParallel(/Enable=/false);` using the
`HasOrderedDirective` (which tests for the presence of an
`OMPOrderedDirective`).
- This results in no longer incorrectly vectorizing the loop when the
`omp simd ordered` directive is present.
Motivation: We'd like to prevent incorrect vectorization of the loops
marked with the `#pragma omp ordered simd` directive which has
previously resulted in miscompiled code.
At the same time, we'd like the usage outside of the `#pragma omp
ordered simd` context to remain unaffected: Note that in the test
"clang/test/OpenMP/ordered_codegen.cpp" we only "lose" the
`!llvm.access.group` metadata in `foo_simd` alone.
This is conservative, in that it's possible some of the loops would be
possible to vectorize, but we prefer to avoid miscompilation of the
loops that are currently illegal to vectorize.
A concrete example follows:
```cpp
// "test.c"
#include <float.h>
#include <math.h>
#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int compare_float(float x1, float x2, float scalar) {
const float diff = fabsf(x1 - x2);
x1 = fabsf(x1);
x2 = fabsf(x2);
const float l = (x2 > x1) ? x2 : x1;
if (diff <= l * scalar * FLT_EPSILON)
return 1;
else
return 0;
}
#define ARRAY_SIZE 256
__attribute__((noinline)) void initialization_loop(
float X[ARRAY_SIZE][ARRAY_SIZE], float Y[ARRAY_SIZE][ARRAY_SIZE]) {
const float max = 1000.0;
srand(time(NULL));
for (int r = 0; r < ARRAY_SIZE; r++) {
for (int c = 0; c < ARRAY_SIZE; c++) {
X[r][c] = ((float)rand() / (float)(RAND_MAX)) * max;
Y[r][c] = X[r][c];
}
}
}
__attribute__((noinline)) void omp_simd_loop(float X[ARRAY_SIZE][ARRAY_SIZE]) {
for (int r = 1; r < ARRAY_SIZE; ++r) {
for (int c = 1; c < ARRAY_SIZE; ++c) {
#pragma omp simd
for (int k = 2; k < ARRAY_SIZE; ++k) {
#pragma omp ordered simd
X[r][k] = X[r][k - 2] + sinf((float)(r / c));
}
}
}
}
__attribute__((noinline)) int comparison_loop(float X[ARRAY_SIZE][ARRAY_SIZE],
float Y[ARRAY_SIZE][ARRAY_SIZE]) {
int totalErrors_simd = 0;
const float scalar = 1.0;
for (int r = 1; r < ARRAY_SIZE; ++r) {
for (int c = 1; c < ARRAY_SIZE; ++c) {
for (int k = 2; k < ARRAY_SIZE; ++k) {
Y[r][k] = Y[r][k - 2] + sinf((float)(r / c));
}
}
// check row for simd update
for (int k = 0; k < ARRAY_SIZE; ++k) {
if (!compare_float(X[r][k], Y[r][k], scalar)) {
++totalErrors_simd;
}
}
}
return totalErrors_simd;
}
int main(void) {
float X[ARRAY_SIZE][ARRAY_SIZE];
float Y[ARRAY_SIZE][ARRAY_SIZE];
initialization_loop(X, Y);
omp_simd_loop(X);
const int totalErrors_simd = comparison_loop(X, Y);
if (totalErrors_simd) {
fprintf(stdout, "totalErrors_simd: %d \n", totalErrors_simd);
fprintf(stdout, "%s : %d - FAIL: error in ordered simd computation.\n",
__FILE__, __LINE__);
} else {
fprintf(stdout, "Success!\n");
}
return totalErrors_simd;
}
```
Before:
```
$ clang -fopenmp-simd -O3 -ffast-math -lm test.c -o test && ./test
totalErrors_simd: 15408
test.c : 76 - FAIL: error in ordered simd computation.
```
clang 19.1.0: https://godbolt.org/z/6EvhxqEhe
After:
```
$ clang -fopenmp-simd -O3 -ffast-math test.c -o test && ./test
Success!
```
Co-authored-by: Matt P. Dziubinski <matt-p.dziubinski@hpe.com>
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(#126079)
Reverts llvm/llvm-project#123867 to fix the test failures
https://lab.llvm.org/buildbot/#/builders/144/builds/17521
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A proposed fix for #95611 [OpenMP][SIMD] ordered has no effect in a loop
SIMD region as of LLVM 18.1.0
Changes:
- Implement new lowering behavior: Conservatively serialize "omp simd"
loops that have `omp simd ordered` directive to prevent incorrect
vectorization (which results in incorrect execution behavior of the
miscompiled program).
Implementation outline:
- We start with the optimistic default initial value of
`LoopStack.setParallel(/Enable=/true);` in
`CodeGenFunction::EmitOMPSimdInit(const OMPLoopDirective &D)`.
- We only disable the loop parallel memory access assumption with `if
(HasOrderedDirective) LoopStack.setParallel(/Enable=/false);` using the
`HasOrderedDirective` (which tests for the presence of an
`OMPOrderedDirective`).
- This results in no longer incorrectly vectorizing the loop when the
`omp simd ordered` directive is present.
Motivation: We'd like to prevent incorrect vectorization of the loops
marked with the `#pragma omp ordered simd` directive which has
previously resulted in miscompiled code.
At the same time, we'd like the usage outside of the `#pragma omp
ordered simd` context to remain unaffected: Note that in the test
"clang/test/OpenMP/ordered_codegen.cpp" we only "lose" the
`!llvm.access.group` metadata in `foo_simd` alone.
This is conservative, in that it's possible some of the loops would be
possible to vectorize, but we prefer to avoid miscompilation of the
loops that are currently illegal to vectorize.
A concrete example follows:
```cpp
// "test.c"
#include <float.h>
#include <math.h>
#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int compare_float(float x1, float x2, float scalar) {
const float diff = fabsf(x1 - x2);
x1 = fabsf(x1);
x2 = fabsf(x2);
const float l = (x2 > x1) ? x2 : x1;
if (diff <= l * scalar * FLT_EPSILON)
return 1;
else
return 0;
}
#define ARRAY_SIZE 256
__attribute__((noinline)) void initialization_loop(
float X[ARRAY_SIZE][ARRAY_SIZE], float Y[ARRAY_SIZE][ARRAY_SIZE]) {
const float max = 1000.0;
srand(time(NULL));
for (int r = 0; r < ARRAY_SIZE; r++) {
for (int c = 0; c < ARRAY_SIZE; c++) {
X[r][c] = ((float)rand() / (float)(RAND_MAX)) * max;
Y[r][c] = X[r][c];
}
}
}
__attribute__((noinline)) void omp_simd_loop(float X[ARRAY_SIZE][ARRAY_SIZE]) {
for (int r = 1; r < ARRAY_SIZE; ++r) {
for (int c = 1; c < ARRAY_SIZE; ++c) {
#pragma omp simd
for (int k = 2; k < ARRAY_SIZE; ++k) {
#pragma omp ordered simd
X[r][k] = X[r][k - 2] + sinf((float)(r / c));
}
}
}
}
__attribute__((noinline)) int comparison_loop(float X[ARRAY_SIZE][ARRAY_SIZE],
float Y[ARRAY_SIZE][ARRAY_SIZE]) {
int totalErrors_simd = 0;
const float scalar = 1.0;
for (int r = 1; r < ARRAY_SIZE; ++r) {
for (int c = 1; c < ARRAY_SIZE; ++c) {
for (int k = 2; k < ARRAY_SIZE; ++k) {
Y[r][k] = Y[r][k - 2] + sinf((float)(r / c));
}
}
// check row for simd update
for (int k = 0; k < ARRAY_SIZE; ++k) {
if (!compare_float(X[r][k], Y[r][k], scalar)) {
++totalErrors_simd;
}
}
}
return totalErrors_simd;
}
int main(void) {
float X[ARRAY_SIZE][ARRAY_SIZE];
float Y[ARRAY_SIZE][ARRAY_SIZE];
initialization_loop(X, Y);
omp_simd_loop(X);
const int totalErrors_simd = comparison_loop(X, Y);
if (totalErrors_simd) {
fprintf(stdout, "totalErrors_simd: %d \n", totalErrors_simd);
fprintf(stdout, "%s : %d - FAIL: error in ordered simd computation.\n",
__FILE__, __LINE__);
} else {
fprintf(stdout, "Success!\n");
}
return totalErrors_simd;
}
```
Before:
```
$ clang -fopenmp-simd -O3 -ffast-math -lm test.c -o test && ./test
totalErrors_simd: 15408
test.c : 76 - FAIL: error in ordered simd computation.
```
clang 19.1.0: https://godbolt.org/z/6EvhxqEhe
After:
```
$ clang -fopenmp-simd -O3 -ffast-math test.c -o test && ./test
Success!
```
Co-authored-by: Matt P. Dziubinski <matt-p.dziubinski@hpe.com>
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Add nuw attribute to inbounds GEPs where the expression used to form the
GEP is an addition of unsigned indices.
Relands #105496, which was reverted because it exposed a miscompilation
arising from #98608. This is now fixed by #106512.
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Reverts llvm/llvm-project#105496
This patch breaks:
https://lab.llvm.org/buildbot/#/builders/25/builds/1952
https://lab.llvm.org/buildbot/#/builders/52/builds/1775
Somehow output is different with sanitizers.
Maybe non-determinism in the code?
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Add nuw attribute to inbounds GEPs where the expression used to form the
GEP is an addition of unsigned indices.
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This patch fixes the dynamic schedule tracking.
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Just re-running the script to make future updates easier
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OMPIRBuilder
Migrate createForStaticInitFunction, createDispatchInitFunction, createDispatchNextFunction and createDispatchFiniFunction from Clang CodeGen to OMPIRBuilder.
Differential Revision: https://reviews.llvm.org/D157994
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The script changes over time and unrelated changes to the test check
lines should not pollute future revisions.
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Conversion performed using the script at:
https://gist.github.com/nikic/98357b71fd67756b0f064c9517b62a34
These are only tests where no manual fixup was required.
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I used a script to reuse existing check lines rather than creating new
ones. There are more opportunities to reduce the line count but the
"check generated functions" logic makes that somewhat tricky.
FWIW, we really should redo the update script with all these use cases
in mind...
Differential Revision: https://reviews.llvm.org/D128686
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The callback is expected to create a branch to the ContinuationBB (sometimes called FiniBB in some lambdas) argument when finishing. This creates problems:
1. The InsertPoint used for CodeGenIP does not need to be the end of a block. If it is not, a naive callback will insert a branch instruction into the middle of the block.
2. The BasicBlock the CodeGenIP is pointing to may or may not have a terminator. There is an conflict where to branch to if the block already has a terminator.
3. Some API functions work only with block having a terminator. Some workarounds have been used to insert a temporary terminator that is removed again.
4. Some callbacks are sensitive to whether the BasicBlock has a terminator or not. This creates a callback ordering problem where different callback may have different behaviour depending on whether a previous callback created a terminator or not. The problem also exists for FinalizeCallbackTy where some callbacks do create branch to another "continue" block, but unlike BodyGenCallbackTy does not receive the target as argument. This is not addressed in this patch.
With this patch, the callback receives an CodeGenIP into a BasicBlock where to insert instructions. If it has to insert control flow, it can split the block at that position as needed but otherwise no separate ContinuationBB is needed. In particular, a callback can be empty without breaking the emitted IR. If the caller needs the control flow to branch to a specific target, it can insert the branch instruction itself and pass an InsertPoint before the terminator to the callback.
Certain frontends such as Clang may expect the current IRBuilder position to be at the end of a basic block. In this case its callbacks must split the block at CodeGenIP before setting the IRBuilder position such that the instructions after CodeGenIP are moved to another basic block and before returning create a new branch instruction to the split block.
Some utility functions such as `splitBB` are supporting correct splitting of BasicBlocks, independent of whether they have a terminator or not, returning/setting the InsertPoint of an IRBuilder to the end of split predecessor block, and optionally omitting creating a branch to the split successor block to be added later.
Reviewed By: kiranchandramohan
Differential Revision: https://reviews.llvm.org/D118409
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This adds -no-opaque-pointers to clang tests whose output will
change when opaque pointers are enabled by default. This is
intended to be part of the migration approach described in
https://discourse.llvm.org/t/enabling-opaque-pointers-by-default/61322/9.
The patch has been produced by replacing %clang_cc1 with
%clang_cc1 -no-opaque-pointers for tests that fail with opaque
pointers enabled. Worth noting that this doesn't cover all tests,
there's a remaining ~40 tests not using %clang_cc1 that will need
a followup change.
Differential Revision: https://reviews.llvm.org/D123115
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turn it off by default
Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.
Test updates are made as a separate patch: D108453
Reviewed By: eugenis
Differential Revision: https://reviews.llvm.org/D105169
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disable-noundef-analysis and turn it off by default"
This reverts commit aacfbb953eb705af2ecfeb95a6262818fa85dd92.
Revert "Fix lit test failures in CodeGenCoroutines"
This reverts commit 63fff0f5bffe20fa2c84a45a41161afa0043cb34.
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turn it off by default
Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.
Test updates are made as a separate patch: D108453
Reviewed By: eugenis
Differential Revision: https://reviews.llvm.org/D105169
[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default (2)
This patch updates test files after D105169.
Autogenerated test codes are changed by `utils/update_cc_test_checks.py,` and non-autogenerated test codes are changed as follows:
(1) I wrote a python script that (partially) updates the tests using regex: {F18594904} The script is not perfect, but I believe it gives hints about which patterns are updated to have `noundef` attached.
(2) The remaining tests are updated manually.
Reviewed By: eugenis
Differential Revision: https://reviews.llvm.org/D108453
Resolve lit failures in clang after 8ca4b3e's land
Fix lit test failures in clang-ppc* and clang-x64-windows-msvc
Fix missing failures in clang-ppc64be* and retry fixing clang-x64-windows-msvc
Fix internal_clone(aarch64) inline assembly
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disable-noundef-analysis and turn it off by default"
This reverts commit 7584ef766a7219b6ee5a400637206d26e0fa98ac.
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turn it off by default
Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.
Test updates are made as a separate patch: D108453
Reviewed By: eugenis
Differential Revision: https://reviews.llvm.org/D105169
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This reverts the following commits:
37ca7a795b277c20c02a218bf44052278c03344b
9aa6c72b92b6c89cc6d23b693257df9af7de2d15
705387c5074bcca36d626882462ebbc2bcc3bed4
8ca4b3ef19fe82d7ad6a6e1515317dcc01b41515
80dba72a669b5416e97a42fd2c2a7bc5a6d3f44a
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turn it off by default (2)
This patch updates test files after D105169.
Autogenerated test codes are changed by `utils/update_cc_test_checks.py,` and non-autogenerated test codes are changed as follows:
(1) I wrote a python script that (partially) updates the tests using regex: {F18594904} The script is not perfect, but I believe it gives hints about which patterns are updated to have `noundef` attached.
(2) The remaining tests are updated manually.
Reviewed By: eugenis
Differential Revision: https://reviews.llvm.org/D108453
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Add support for ordered directive in the OpenMPIRBuilder.
This patch also modidies clang to use the ordered directive when the
option -fopenmp-enable-irbuilder is enabled.
Also fix one ICE when parsing one canonical for loop with the relational
operator LE or GE in openmp region by replacing unary increment
operation of the expression of the variable "Expr A" minus the variable
"Expr B" (++(Expr A - Expr B)) with binary addition operation of the
experssion of the variable "Expr A" minus the variable "Expr B" and the
expression with constant value "1" (Expr A - Expr B + "1").
Reviewed By: Meinersbur, kiranchandramohan
Differential Revision: https://reviews.llvm.org/D107430
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This patch adds a module level metadata flag indicating that the module
was compiled with the `-fopenmp` flag. This will make it easier for
passes like OpenMPOpt to determine if it should be run.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D102361
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This patch refactors a subset of Clang OpenMP tests, generating checklines using the update_cc_test_checks script. This refactoring facilitates updating the Clang OpenMP code generation codebase by automating test generation.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D101849
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This reverts commit 956cae2f09b21429dbcb02066c99e35a239aa4bf.
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This patch refactors a subset of Clang OpenMP tests, generating checklines using the update_cc_test_checks script. This refactoring facilitates updating the Clang OpenMP code generation codebase by automating test generation.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D101849
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Replace the `ident_t` handling in Clang with the methods offered by the
OMPIRBuilder. This cuts down on the clang code as well as the
differences between the two, making further transitions easier. Tests
have changed but there should not be a real functional change. The most
interesting difference is probably that we stop generating local ident_t
allocations for now and just use globals. Given that this happens only
with debug info, the location part of the `ident_t` is probably bigger
than the test anyway. As the location part is already a global, we can
avoid the allocation, memcpy, and store in favor of a constant global
that is slightly bigger. This can be revisited if there are
complications.
Reviewed By: ABataev
Differential Revision: https://reviews.llvm.org/D80735
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Summary:
When -fopenmp option is specified then version 5.0 will be set as
default.
Reviewers: gregrodgers, jdoerfert, ABataev
Reviewed By: ABataev
Subscribers: pdhaliwal, yaxunl, guansong, sstefan1, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D81098
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If we're going to assume references are dereferenceable, we should also
assume they're aligned: otherwise, we can't actually dereference them.
See also D80072.
Differential Revision: https://reviews.llvm.org/D80166
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According to the report, better to keep the original strict compare
operation as the loop condition with unsigned loop counters to make the
loop countable. This allows further loop transformations.
llvm-svn: 352526
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llvm.mem.parallel_loop_access metadata.
Instead of generating llvm.mem.parallel_loop_access metadata, generate
llvm.access.group on instructions and llvm.loop.parallel_accesses on
loops. There is one access group per generated loop.
This is clang part of D52116/r349725.
Differential Revision: https://reviews.llvm.org/D52117
llvm-svn: 349823
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Currently ident_t objects are created const when debug info is not
enabled, but the libittnotify libray in the OpenMP runtime writes to
the reserved_2 field (See __kmp_itt_region_forking in
openmp/runtime/src/kmp_itt.inl). Now create ident_t objects non-const.
Differential Revision: https://reviews.llvm.org/D51331
llvm-svn: 340934
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only.
Added support for -fopenmp-simd option that allows compilation of
simd-based constructs without emission of OpenMP runtime calls.
llvm-svn: 321560
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llvm-svn: 310098
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Clang can generate LLVM IR for x86 without a registered x86 backend.
llvm-svn: 284836
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modifiers.
OpenMP 4.5 adds support for monotonic/nonmonotonic modifiers in 'schedule' clause. Add codegen for these modifiers.
llvm-svn: 256666
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OpenMP 4.5 allows to use 'ordered' clause without parameter on 'loop simd' constructs.
llvm-svn: 256639
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Description.
If the simd clause is specified, the ordered regions encountered by any thread will use only a single SIMD lane to execute the ordered regions in the order of the loop iterations.
Restrictions.
An ordered construct with the simd clause is the only OpenMP construct that can appear in the simd region.
An ordered directive with ‘simd’ clause is generated as an outlined function and corresponding function call to prevent this part of code from vectorization later in backend.
llvm-svn: 248772
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OpenMP 4.1 extends format of '#pragma omp ordered'. It adds 3 additional clauses: 'threads', 'simd' and 'depend'.
If no clause is specified, the ordered construct behaves as if the threads clause had been specified. If the threads clause is specified, the threads in the team executing the loop region execute ordered regions sequentially in the order of the loop iterations.
The loop region to which an ordered region without any clause or with a threads clause binds must have an ordered clause without the parameter specified on the corresponding loop directive.
llvm-svn: 248569
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of the llvm targets from clang/CodeGen into ClangCheck.cpp and CIndex.cpp.
llvm-svn: 241653
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failures.
llvm-svn: 241642
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r241620.
llvm-svn: 241623
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Generate the next code for 'cancellation point':
if (__kmpc_cancellationpoint()) {
__kmpc_cancel_barrier();
<exit construct>;
}
llvm-svn: 241336
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loops with ordered clause must be generated the same way as dynamic loops, but with static scheduleing.
llvm-svn: 237788
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-fopenmp turns on OpenMP support and links libiomp5 as OpenMP library. Also there is -fopenmp={libiomp5|libgomp} option that allows to override effect of -fopenmp and link libgomp library (if -fopenmp=libgomp is specified).
Differential Revision: http://reviews.llvm.org/D9736
llvm-svn: 237769
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dynamic/guided scheduling.
Inner bodies of OpenMP worksharing loop-based constructs with dynamic or guided scheduling are allowed to be marked with !llvm.mem.parallel_loop_access metadata for better optimization. Worksharing constructs with static scheduling cannot be marked this way (according to OpenMP standard "A data dependence between the same logical iterations in two such loops is guaranteed").
Constructs with auto and runtime scheduling are also not marked because automatically chosen scheduling may be static also.
Differential Revision: http://reviews.llvm.org/D9518
llvm-svn: 236693
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Add codegen for 'ordered' directive:
__kmpc_ordered(ident_t *, gtid);
<associated statement>;
__kmpc_end_ordered(ident_t *, gtid);
Also for 'for' directives with the dynamic scheduling and an 'ordered' clause added a call to '__kmpc_dispatch_fini_(4|8)[u]()' function after increment expression for loop control variable:
while(__kmpc_dispatch_next(&LB, &UB)) {
idx = LB;
while (idx <= UB) { BODY; ++idx;
__kmpc_dispatch_fini_(4|8)[u](); // For ordered loops only.
} // inner loop
}
Differential Revision: http://reviews.llvm.org/D9070
llvm-svn: 235496
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