[llvm] r326181 - [NewGVN] Update phi-of-ops def block when updating existing ValuePHI.

[Florian Hahn via llvm-commits]

Author: fhahn
Date: Tue Feb 27 01:34:51 2018
New Revision: 326181

URL: http://llvm.org/viewvc/llvm-project?rev=326181&view=rev
Log:
[NewGVN] Update phi-of-ops def block when updating existing ValuePHI.

In case we update a ValuePHI node created earlier, we could update it
based on a different OpPHI which could be in a different block.
We need to update the TempToBlock mapping reflecting the new block,
otherwise we would end up placing the new phi node in a wrong block.

This problem is exposed by the test case in
https://bugs.llvm.org/show_bug.cgi?id=36504.

This patch fixes a slightly simpler problem than in the bug report. In
the bug's re-producer, the additional problem is that we are re-using a
ValuePHI node with to few incoming values for the new OpPHI. If this
patch makes sense, I will follow it up with a patch that creates a new
PHI node if the existing PHI node has a different number of incoming
values.

Reviewers: davide, dberlin

Reviewed By: dberlin

Differential Revision: https://reviews.llvm.org/D43770

Added:
    llvm/trunk/test/Transforms/NewGVN/phi-of-ops-move-block.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/NewGVN.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/NewGVN.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/NewGVN.cpp?rev=326181&r1=326180&r2=326181&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/NewGVN.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/NewGVN.cpp Tue Feb 27 01:34:51 2018
@@ -2819,6 +2819,7 @@ NewGVN::makePossiblePHIOfOps(Instruction
       for (auto PHIOp : Ops)
         ValuePHI->addIncoming(PHIOp.first, PHIOp.second);
     } else {
+      TempToBlock[ValuePHI] = PHIBlock;
       unsigned int i = 0;
       for (auto PHIOp : Ops) {
         ValuePHI->setIncomingValue(i, PHIOp.first);

Added: llvm/trunk/test/Transforms/NewGVN/phi-of-ops-move-block.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/NewGVN/phi-of-ops-move-block.ll?rev=326181&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/NewGVN/phi-of-ops-move-block.ll (added)
+++ llvm/trunk/test/Transforms/NewGVN/phi-of-ops-move-block.ll Tue Feb 27 01:34:51 2018
@@ -0,0 +1,56 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -newgvn -S | FileCheck %s
+
+ at g_20 = external global i32, align 4
+
+define void @test() {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[BB1:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[STOREMERGE:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[ADD1:%.*]], [[CRITEDGE:%.*]] ]
+; CHECK-NEXT:    store i32 [[STOREMERGE]], i32* @g_20, align 4
+; CHECK-NEXT:    [[CMP0:%.*]] = icmp eq i32 [[STOREMERGE]], 0
+; CHECK-NEXT:    br i1 [[CMP0]], label [[LR_PH:%.*]], label [[CRITEDGE]]
+; CHECK:       lr.ph:
+; CHECK-NEXT:    [[LV:%.*]] = load i64, i64* inttoptr (i64 16 to i64*), align 16
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp eq i64 [[LV]], 0
+; CHECK-NEXT:    br i1 [[CMP1]], label [[PREHEADER_SPLIT:%.*]], label [[CRITEDGE]]
+; CHECK:       preheader.split:
+; CHECK-NEXT:    br label [[PREHEADER_SPLIT]]
+; CHECK:       critedge:
+; CHECK-NEXT:    [[PHIOFOPS1:%.*]] = phi i1 [ false, [[BB1]] ], [ true, [[LR_PH]] ]
+; CHECK-NEXT:    [[PHIOFOPS:%.*]] = phi i1 [ [[CMP0]], [[BB1]] ], [ true, [[LR_PH]] ]
+; CHECK-NEXT:    [[DOT05_LCSSA:%.*]] = phi i32 [ 0, [[BB1]] ], [ -1, [[LR_PH]] ]
+; CHECK-NEXT:    [[ADD1]] = add nsw i32 [[STOREMERGE]], -1
+; CHECK-NEXT:    br i1 [[PHIOFOPS]], label [[BB1]], label [[END:%.*]]
+; CHECK:       end:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %bb1
+
+bb1:                                      ; preds = %critedge, %entry
+  %storemerge = phi i32 [ 0, %entry ], [ %add1, %critedge ]
+  store i32 %storemerge, i32* @g_20, align 4
+  %cmp0 = icmp eq i32 %storemerge, 0
+  br i1 %cmp0, label %lr.ph, label %critedge
+
+lr.ph:                                           ; preds = %bb1
+  %lv = load i64, i64* inttoptr (i64 16 to i64*), align 16
+  %cmp1 = icmp eq i64 %lv, 0
+  br i1 %cmp1, label %preheader.split, label %critedge
+
+preheader.split:                                 ; preds = %lr.ph, %preheader.split
+  br label %preheader.split
+
+critedge:                                        ; preds = %lr.ph, %bb1
+  %.05.lcssa = phi i32 [ 0, %bb1 ], [ -1, %lr.ph ]
+  %cmp2 = icmp ne i32 %.05.lcssa, 0
+  %brmerge = or i1 %cmp0, %cmp2
+  %add1 = add nsw i32 %storemerge, -1
+  br i1 %brmerge, label %bb1, label %end
+
+end:
+  ret void
+}