[LowerSwitch] Fixed faulty PHI node update

Summary:
When lowerswitch merge several cases into a new default block it's not
updating the PHI nodes accordingly. The code that update the PHI nodes
for the default edge only update the first entry and do not remove the
remaining ones, to make sure the number of entries match the number of
predecessors.

This is easily fixed by replacing the code that update the PHI node with
the already existing utility function for updating PHI nodes.

Reviewers: hans, reames, arsenm

Reviewed By: arsenm

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D47055

llvm-svn: 332960

diff --git a/llvm/lib/Transforms/Utils/LowerSwitch.cpp b/llvm/lib/Transforms/Utils/LowerSwitch.cpp
index 441c5fd8b5af0186a228e431d5ef40e8deae436b..76ad35832dc3d18340f5cca074c72e036c4cae36 100644 (file)
--- a/llvm/lib/Transforms/Utils/LowerSwitch.cpp
+++ b/llvm/lib/Transforms/Utils/LowerSwitch.cpp
@@ -512,25 +512,25 @@ void LowerSwitch::processSwitchInst(SwitchInst *SI,
     }
   }
 
+  unsigned NrOfDefaults = (SI->getDefaultDest() == Default) ? 1 : 0;
+  for (const auto &Case : SI->cases())
+    if (Case.getCaseSuccessor() == Default)
+      NrOfDefaults++;
+
   // Create a new, empty default block so that the new hierarchy of
   // if-then statements go to this and the PHI nodes are happy.
   BasicBlock *NewDefault = BasicBlock::Create(SI->getContext(), "NewDefault");
   F->getBasicBlockList().insert(Default->getIterator(), NewDefault);
   BranchInst::Create(Default, NewDefault);
 
-  // If there is an entry in any PHI nodes for the default edge, make sure
-  // to update them as well.
-  for (BasicBlock::iterator I = Default->begin(); isa<PHINode>(I); ++I) {
-    PHINode *PN = cast<PHINode>(I);
-    int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
-    assert(BlockIdx != -1 && "Switch didn't go to this successor??");
-    PN->setIncomingBlock((unsigned)BlockIdx, NewDefault);
-  }
-
   BasicBlock *SwitchBlock =
       switchConvert(Cases.begin(), Cases.end(), LowerBound, UpperBound, Val,
                     OrigBlock, OrigBlock, NewDefault, UnreachableRanges);
 
+  // If there are entries in any PHI nodes for the default edge, make sure
+  // to update them as well.
+  fixPhis(Default, OrigBlock, NewDefault, NrOfDefaults);
+
   // Branch to our shiny new if-then stuff...
   BranchInst::Create(SwitchBlock, OrigBlock);
 

diff --git a/llvm/test/Transforms/Util/lowerswitch.ll b/llvm/test/Transforms/Util/lowerswitch.ll
index 1eddb43c1a061c3beb4da93ae5349931d2f94080..70e1e239b3dde0b8ad95658e308910e9b862455b 100644 (file)
--- a/llvm/test/Transforms/Util/lowerswitch.ll
+++ b/llvm/test/Transforms/Util/lowerswitch.ll
@@ -3,7 +3,7 @@
 ; Test that we don't crash and have a different basic block for each incoming edge.
 define void @test0() {
 ; CHECK-LABEL: @test0
-; CHECK: %merge = phi i64 [ 1, %BB3 ], [ 0, %NewDefault ], [ 0, %NodeBlock5 ], [ 0, %LeafBlock1 ]
+; CHECK: %merge = phi i64 [ 1, %BB3 ], [ 0, %NodeBlock5 ], [ 0, %LeafBlock1 ], [ 0, %NewDefault ]
 BB1:
   switch i32 undef, label %BB2 [
     i32 3, label %BB2
@@ -186,3 +186,59 @@ define void @test2(i32 %mode) {
 ._crit_edge:                                      ; preds = %34, %0
   ret void
 }
+
+; Test that the PHI node in for.cond should have one entry for each predecessor
+; of its parent basic block after lowerswitch merged several cases into a new
+; default block.
+define void @test3() {
+; CHECK-LABEL: @test3
+entry:
+  br label %lbl1
+
+lbl1:                                             ; preds = %cleanup, %entry
+  br label %lbl2
+
+lbl2:                                             ; preds = %cleanup, %lbl1
+  br label %for.cond
+
+for.cond:                                         ; preds = %cleanup, %cleanup, %lbl2
+; CHECK: for.cond:
+; CHECK: phi i16 [ undef, %lbl2 ], [ %b.3, %NewDefault ]{{$}}
+; CHECK: for.cond1:
+  %b.2 = phi i16 [ undef, %lbl2 ], [ %b.3, %cleanup ], [ %b.3, %cleanup ]
+  br label %for.cond1
+
+for.cond1:                                        ; preds = %for.inc, %for.cond
+  %b.3 = phi i16 [ %b.2, %for.cond ], [ undef, %for.inc ]
+  %tobool = icmp ne i16 %b.3, 0
+  br i1 %tobool, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond1
+  br i1 undef, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  br label %cleanup
+
+for.inc:                                          ; preds = %for.body
+  br label %for.cond1
+
+for.end:                                          ; preds = %for.cond1
+  br i1 undef, label %if.then4, label %for.body7
+
+if.then4:                                         ; preds = %for.end
+  br label %cleanup
+
+for.body7:                                        ; preds = %for.end
+  br label %cleanup
+
+cleanup:                                          ; preds = %for.body7, %if.then4, %if.then
+  switch i32 undef, label %unreachable [
+    i32 0, label %for.cond
+    i32 2, label %lbl1
+    i32 5, label %for.cond
+    i32 3, label %lbl2
+  ]
+
+unreachable:                                      ; preds = %cleanup
+  unreachable
+}