[llvm] r262624 - [LoopUtils, LV] Fix PR26734

[Matthew Simpson via llvm-commits]

Author: mssimpso
Date: Thu Mar  3 10:12:01 2016
New Revision: 262624

URL: http://llvm.org/viewvc/llvm-project?rev=262624&view=rev
Log:
[LoopUtils, LV] Fix PR26734

The vectorization of first-order recurrences (r261346) caused PR26734. When
detecting these recurrences, we need to ensure that the previous value is
actually defined inside the loop. This patch includes the fix and test case.

Modified:
    llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp
    llvm/trunk/test/Transforms/LoopVectorize/AArch64/first-order-recurrence.ll

Modified: llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp?rev=262624&r1=262623&r2=262624&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp Thu Mar  3 10:12:01 2016
@@ -543,7 +543,7 @@ bool RecurrenceDescriptor::isFirstOrderR
   // Get the previous value. The previous value comes from the latch edge while
   // the initial value comes form the preheader edge.
   auto *Previous = dyn_cast<Instruction>(Phi->getIncomingValueForBlock(Latch));
-  if (!Previous)
+  if (!Previous || !TheLoop->contains(Previous))
     return false;
 
   // Ensure every user of the phi node is dominated by the previous value. The

Modified: llvm/trunk/test/Transforms/LoopVectorize/AArch64/first-order-recurrence.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/AArch64/first-order-recurrence.ll?rev=262624&r1=262623&r2=262624&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/AArch64/first-order-recurrence.ll (original)
+++ llvm/trunk/test/Transforms/LoopVectorize/AArch64/first-order-recurrence.ll Thu Mar  3 10:12:01 2016
@@ -207,3 +207,52 @@ for.end.loopexit:
 for.end:
   ret void
 }
+
+; CHECK-LABEL: @PR26734
+;
+; void PR26734(short *a, int *b, int *c, int d, short *e) {
+;   for (; d != 21; d++) {
+;     *b &= *c;
+;     *e = *a - 6;
+;     *c = *e;
+;   }
+; }
+;
+; CHECK-NOT: vector.ph:
+;
+define void @PR26734(i16* %a, i32* %b, i32* %c, i32 %d, i16* %e) {
+entry:
+  %cmp4 = icmp eq i32 %d, 21
+  br i1 %cmp4, label %entry.for.end_crit_edge, label %for.body.lr.ph
+
+entry.for.end_crit_edge:
+  %.pre = load i32, i32* %b, align 4
+  br label %for.end
+
+for.body.lr.ph:
+  %0 = load i16, i16* %a, align 2
+  %sub = add i16 %0, -6
+  %conv2 = sext i16 %sub to i32
+  %c.promoted = load i32, i32* %c, align 4
+  %b.promoted = load i32, i32* %b, align 4
+  br label %for.body
+
+for.body:
+  %inc7 = phi i32 [ %d, %for.body.lr.ph ], [ %inc, %for.body ]
+  %and6 = phi i32 [ %b.promoted, %for.body.lr.ph ], [ %and, %for.body ]
+  %conv25 = phi i32 [ %c.promoted, %for.body.lr.ph ], [ %conv2, %for.body ]
+  %and = and i32 %and6, %conv25
+  %inc = add nsw i32 %inc7, 1
+  %cmp = icmp eq i32 %inc, 21
+  br i1 %cmp, label %for.cond.for.end_crit_edge, label %for.body
+
+for.cond.for.end_crit_edge:
+  %and.lcssa = phi i32 [ %and, %for.body ]
+  store i32 %conv2, i32* %c, align 4
+  store i32 %and.lcssa, i32* %b, align 4
+  store i16 %sub, i16* %e, align 2
+  br label %for.end
+
+for.end:
+  ret void
+}