Metadata for annotating loops as parallel. The first consumer for this
metadata is the loop vectorizer.
See the documentation update for more info.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175060 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp
index 4d4c627..f1ad650 100644
--- a/lib/Analysis/LoopInfo.cpp
+++ b/lib/Analysis/LoopInfo.cpp
@@ -24,6 +24,7 @@
#include "llvm/Assembly/Writer.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Metadata.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
@@ -233,6 +234,55 @@
return true;
}
+bool Loop::isAnnotatedParallel() const {
+
+ BasicBlock *latch = getLoopLatch();
+ if (latch == NULL)
+ return false;
+
+ MDNode *desiredLoopIdMetadata =
+ latch->getTerminator()->getMetadata("llvm.loop.parallel");
+
+ if (!desiredLoopIdMetadata)
+ return false;
+
+ // The loop branch contains the parallel loop metadata. In order to ensure
+ // that any parallel-loop-unaware optimization pass hasn't added loop-carried
+ // dependencies (thus converted the loop back to a sequential loop), check
+ // that all the memory instructions in the loop contain parallelism metadata
+ // that point to the same unique "loop id metadata" the loop branch does.
+ for (block_iterator BB = block_begin(), BE = block_end(); BB != BE; ++BB) {
+ for (BasicBlock::iterator II = (*BB)->begin(), EE = (*BB)->end();
+ II != EE; II++) {
+
+ if (!II->mayReadOrWriteMemory())
+ continue;
+
+ if (!II->getMetadata("llvm.mem.parallel_loop_access"))
+ return false;
+
+ // The memory instruction can refer to the loop identifier metadata
+ // directly or indirectly through another list metadata (in case of
+ // nested parallel loops). The loop identifier metadata refers to
+ // itself so we can check both cases with the same routine.
+ MDNode *loopIdMD =
+ dyn_cast<MDNode>(II->getMetadata("llvm.mem.parallel_loop_access"));
+ bool loopIdMDFound = false;
+ for (unsigned i = 0, e = loopIdMD->getNumOperands(); i < e; ++i) {
+ if (loopIdMD->getOperand(i) == desiredLoopIdMetadata) {
+ loopIdMDFound = true;
+ break;
+ }
+ }
+
+ if (!loopIdMDFound)
+ return false;
+ }
+ }
+ return true;
+}
+
+
/// hasDedicatedExits - Return true if no exit block for the loop
/// has a predecessor that is outside the loop.
bool Loop::hasDedicatedExits() const {