[llvm] r313358 - [RuntimeUnrolling] Populate the VMap entry correctly when default generated through lookup

[Anna Thomas via llvm-commits]

Author: annat
Date: Fri Sep 15 06:29:33 2017
New Revision: 313358

URL: http://llvm.org/viewvc/llvm-project?rev=313358&view=rev
Log:
[RuntimeUnrolling] Populate the VMap entry correctly when default generated through lookup

During runtime unrolling on loops with multiple exits, we update the
exit blocks with the correct phi values from both original and remainder
loop.
In this process, we lookup the VMap for the mapped incoming phi values,
but did not update the VMap if a default entry was generated in the VMap
during the lookup. This default value is generated when constants or
values outside the current loop are looked up.
This patch fixes the assertion failure when null entries are present in
the VMap because of this lookup. Added a testcase that showcases the
problem.

Modified:
    llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp
    llvm/trunk/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll

Modified: llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp?rev=313358&r1=313357&r2=313358&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp Fri Sep 15 06:29:33 2017
@@ -782,11 +782,15 @@ bool llvm::UnrollRuntimeLoopRemainder(Lo
      // Add the incoming values from the remainder code to the end of the phi
      // node.
      for (unsigned i =0; i < oldNumOperands; i++){
-       Value *newVal = VMap[Phi->getIncomingValue(i)];
+       Value *newVal = VMap.lookup(Phi->getIncomingValue(i));
        // newVal can be a constant or derived from values outside the loop, and
-       // hence need not have a VMap value.
-       if (!newVal)
+       // hence need not have a VMap value. Also, since lookup already generated
+       // a default "null" VMap entry for this value, we need to populate that
+       // VMap entry correctly, with the mapped entry being itself.
+       if (!newVal) {
          newVal = Phi->getIncomingValue(i);
+         VMap[Phi->getIncomingValue(i)] = Phi->getIncomingValue(i);
+       }
        Phi->addIncoming(newVal,
                            cast<BasicBlock>(VMap[Phi->getIncomingBlock(i)]));
      }

Modified: llvm/trunk/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll?rev=313358&r1=313357&r2=313358&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll (original)
+++ llvm/trunk/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll Fri Sep 15 06:29:33 2017
@@ -4,6 +4,8 @@
 ; RUN: opt < %s -loop-unroll -unroll-runtime=true -unroll-runtime-epilog=false -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine -S | FileCheck %s -check-prefix=PROLOG
 ; RUN: opt < %s -loop-unroll -unroll-runtime -unroll-runtime-epilog=false -unroll-count=2 -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine
 
+; REQUIRES: asserts
+
 ; the third and fifth RUNs generate an epilog/prolog remainder block for all the test
 ; cases below (it does not generate a loop).
 
@@ -478,3 +480,45 @@ latch:
 exit:                                              ; preds = %latch
   ret void
 }
+
+declare i8 addrspace(1)* @foo(i32)
+; inner loop prolog unrolled
+; a value from outer loop is used in exit block of inner loop.
+; Don't create VMap entries for such values (%trip).
+define i8 addrspace(1)* @test9(i8* nocapture readonly %arg, i32 %n) {
+; PROLOG: test9(
+; PROLOG: header.prol:
+; PROLOG-NEXT: %phi.prol = phi i64 [ 0, %header.prol.preheader ], [ %iv.next.prol, %latch.prol ]
+; PROLOG: latch.prol:
+; PROLOG-NOT: trip
+; PROLOG:     br i1 %prol.iter.cmp, label %header.prol.loopexit.unr-lcssa, label %header.prol
+bb:
+  br label %outerloopHdr
+
+outerloopHdr:                                              ; preds = %outerLatch, %bb
+  %trip = add i32 %n, -1
+  %outercnd = icmp slt i32 0, %trip
+  br i1 %outercnd, label %preheader, label %outerLatch
+
+preheader:                                              ; preds = %outerloopHdr
+  %tmp4 = zext i32 0 to i64
+  br label %header
+
+header:                                              ; preds = %latch, %preheader
+  %phi = phi i64 [ %tmp4, %preheader ], [ %iv.next, %latch ]
+  %tmp7 = trunc i64 %phi to i32
+  br i1 true, label %latch, label %innerexit
+
+innerexit:                                              ; preds = %header
+  %tmp9 = call i8 addrspace(1)* @foo(i32 %trip)
+  ret i8 addrspace(1)* %tmp9
+
+latch:                                             ; preds = %header
+  %tmp11 = add nsw i32 %tmp7, 1
+  %innercnd = icmp slt i32 %tmp11, %trip
+  %iv.next = add nuw nsw i64 %phi, 1
+  br i1 %innercnd, label %header, label %outerLatch
+
+outerLatch:                                             ; preds = %latch, %outerloopHdr
+  br label %outerloopHdr
+}