[Openmp-commits] [PATCH] D40171: Fix for OMP doacross implementation on 32-bit platforms

[Andrey Churbanov via Phabricator via Openmp-commits]

AndreyChurbanov created this revision.

The bug was in the size of integer used to interpret pointer for CAS operation.
The fix is to use 32-bit integer for 32-bit platform, and 64-bit otherwise.


Repository:
  rL LLVM

https://reviews.llvm.org/D40171

Files:
  runtime/src/kmp_csupport.cpp


Index: runtime/src/kmp_csupport.cpp
===================================================================
--- runtime/src/kmp_csupport.cpp
+++ runtime/src/kmp_csupport.cpp
@@ -3802,23 +3802,30 @@
     __kmp_wait_yield_4((volatile kmp_uint32 *)&sh_buf->doacross_buf_idx, idx,
                        __kmp_eq_4, NULL);
   }
+#if KMP_32_BIT_ARCH
   // Check if we are the first thread. After the CAS the first thread gets 0,
   // others get 1 if initialization is in progress, allocated pointer otherwise.
+  // Treat pointer as volatile integer (value 0 or 1) until memory is allocated.
+  flags = (kmp_uint32 *)KMP_COMPARE_AND_STORE_RET32(
+      (volatile kmp_int32 *)&sh_buf->doacross_flags, NULL, 1);
+#else
   flags = (kmp_uint32 *)KMP_COMPARE_AND_STORE_RET64(
-      (kmp_int64 *)&sh_buf->doacross_flags, NULL, (kmp_int64)1);
+      (volatile kmp_int64 *)&sh_buf->doacross_flags, NULL, 1LL);
+#endif
   if (flags == NULL) {
     // we are the first thread, allocate the array of flags
-    kmp_int64 size =
-        trace_count / 8 + 8; // in bytes, use single bit per iteration
+    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);
-  } else if ((kmp_int64)flags == 1) {
+  } else if (flags == (kmp_uint32 *)1) {
+#if KMP_32_BIT_ARCH
     // initialization is still in progress, need to wait
-    while ((volatile kmp_int64)sh_buf->doacross_flags == 1) {
+    while (*(volatile kmp_int32 *)&sh_buf->doacross_flags == 1)
+#else
+    while (*(volatile kmp_int64 *)&sh_buf->doacross_flags == 1LL)
+#endif
       KMP_YIELD(TRUE);
-    }
   }
-  KMP_DEBUG_ASSERT((kmp_int64)sh_buf->doacross_flags >
-                   1); // check value of pointer
+  KMP_DEBUG_ASSERT(sh_buf->doacross_flags > (kmp_uint32 *)1); // check ptr value
   pr_buf->th_doacross_flags =
       sh_buf->doacross_flags; // save private copy in order to not
   // touch shared buffer on each iteration


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