[Openmp-commits] [PATCH] D40175: Fix for OMP doacross implementation on Power

[Jonas Hahnfeld via Phabricator via Openmp-commits]

Hahnfeld updated this revision to Diff 123935.
Hahnfeld marked an inline comment as done.
Hahnfeld edited the summary of this revision.
Hahnfeld added a comment.

Add `KMP_MB()` in `__kmpc_doacross_post` after discussion with @AlexEichenberger.


https://reviews.llvm.org/D40175

Files:
  runtime/src/kmp_csupport.cpp
  runtime/test/worksharing/for/kmp_doacross_check.c


Index: runtime/test/worksharing/for/kmp_doacross_check.c
===================================================================
--- runtime/test/worksharing/for/kmp_doacross_check.c
+++ runtime/test/worksharing/for/kmp_doacross_check.c
@@ -24,7 +24,7 @@
   dims.lo = 1;
   dims.up = N-1;
   dims.st = 1;
-  #pragma omp parallel
+  #pragma omp parallel num_threads(4)
   {
     int i, gtid;
     long long vec;
Index: runtime/src/kmp_csupport.cpp
===================================================================
--- runtime/src/kmp_csupport.cpp
+++ runtime/src/kmp_csupport.cpp
@@ -3815,15 +3815,20 @@
   if (flags == NULL) {
     // we are the first thread, allocate the array of flags
     size_t size = trace_count / 8 + 8; // in bytes, use single bit per iteration
-    sh_buf->doacross_flags = (kmp_uint32 *)__kmp_thread_calloc(th, size, 1);
+    flags = (kmp_uint32 *)__kmp_thread_calloc(th, size, 1);
+    KMP_MB();
+    sh_buf->doacross_flags = flags;
   } else if (flags == (kmp_uint32 *)1) {
 #if KMP_32_BIT_ARCH
     // initialization is still in progress, need to wait
     while (*(volatile kmp_int32 *)&sh_buf->doacross_flags == 1)
 #else
     while (*(volatile kmp_int64 *)&sh_buf->doacross_flags == 1LL)
 #endif
       KMP_YIELD(TRUE);
+    KMP_MB();
+  } else {
+    KMP_MB();
   }
   KMP_DEBUG_ASSERT(sh_buf->doacross_flags > (kmp_uint32 *)1); // check ptr value
   pr_buf->th_doacross_flags =
@@ -3919,6 +3924,7 @@
   while ((flag & pr_buf->th_doacross_flags[iter_number]) == 0) {
     KMP_YIELD(TRUE);
   }
+  KMP_MB();
   KA_TRACE(20,
            ("__kmpc_doacross_wait() exit: T#%d wait for iter %lld completed\n",
             gtid, (iter_number << 5) + shft));
@@ -3971,6 +3977,7 @@
   shft = iter_number % 32; // use 32-bit granularity
   iter_number >>= 5; // divided by 32
   flag = 1 << shft;
+  KMP_MB();
   if ((flag & pr_buf->th_doacross_flags[iter_number]) == 0)
     KMP_TEST_THEN_OR32(&pr_buf->th_doacross_flags[iter_number], flag);
   KA_TRACE(20, ("__kmpc_doacross_post() exit: T#%d iter %lld posted\n", gtid,


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