Masked Store in Loop Vectorizer - bugfix

Fixed a bug in loop vectorization with conditional store.

Differential Revision: http://reviews.llvm.org/D19532

llvm-svn: 267597

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -4909,24 +4909,20 @@ bool LoopVectorizationLegality::blockCanBePredicated(BasicBlock *BB,
       if (!SI)
         return false;
 
+      // Build a masked store if it is legal for the target.
+      if (isLegalMaskedStore(SI->getValueOperand()->getType(),
+                             SI->getPointerOperand()) ||
+          isLegalMaskedScatter(SI->getValueOperand()->getType())) {
+        MaskedOp.insert(SI);
+        continue;
+      }
+
       bool isSafePtr = (SafePtrs.count(SI->getPointerOperand()) != 0);
       bool isSinglePredecessor = SI->getParent()->getSinglePredecessor();
 
       if (++NumPredStores > NumberOfStoresToPredicate || !isSafePtr ||
-          !isSinglePredecessor) {
-        // Build a masked store if it is legal for the target, otherwise
-        // scalarize the block.
-        bool isLegalMaskedOp =
-          isLegalMaskedStore(SI->getValueOperand()->getType(),
-                             SI->getPointerOperand()) ||
-          isLegalMaskedScatter(SI->getValueOperand()->getType());
-        if (isLegalMaskedOp) {
-          --NumPredStores;
-          MaskedOp.insert(SI);
-          continue;
-        }
+          !isSinglePredecessor)
         return false;
-      }
     }
     if (it->mayThrow())
       return false;

llvm/test/Transforms/LoopVectorize/X86/max-mstore.ll

@@ -0,0 +1,46 @@
+; RUN: opt -basicaa -loop-vectorize -force-vector-interleave=1 -S -mcpu=core-avx2
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@b = common global [256 x i32] zeroinitializer, align 16
+@a = common global [256 x i32] zeroinitializer, align 16
+
+; unsigned int a[256], b[256];
+; void foo() {
+;  for (i = 0; i < 256; i++) {
+;    if (b[i] > a[i])
+;      a[i] = b[i];
+;  }
+; }
+
+; CHECK-LABEL: foo
+; CHECK: load <8 x i32>
+; CHECK: icmp ugt <8 x i32>
+; CHECK: masked.store
+
+define void @foo() {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.inc, %entry
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.inc ]
+  %arrayidx = getelementptr inbounds [256 x i32], [256 x i32]* @b, i64 0, i64 %indvars.iv
+  %0 = load i32, i32* %arrayidx, align 4
+  %arrayidx2 = getelementptr inbounds [256 x i32], [256 x i32]* @a, i64 0, i64 %indvars.iv
+  %1 = load i32, i32* %arrayidx2, align 4
+  %cmp3 = icmp ugt i32 %0, %1
+  br i1 %cmp3, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  store i32 %0, i32* %arrayidx2, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, 256
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.inc
+  ret void
+}