[LoopVersioning] Relax an assert for LCSSA PHIs

When you have multiple LCSSA (single-operand) PHIs that are converted
into two-operand PHIs due to versioning, only assert that the PHI
currently being converted has a single operand.  I.e. we don't want to
check PHIs that were converted earlier in the loop.

Fixes PR27023.

Thanks to Karl-Johan Karlsson for the minimized testcase!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264081 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/LoopVersioning.cpp b/lib/Transforms/Utils/LoopVersioning.cpp
index 19c7fa7..e3f711f 100644 (file)
--- a/lib/Transforms/Utils/LoopVersioning.cpp
+++ b/lib/Transforms/Utils/LoopVersioning.cpp
@@ -133,10 +133,11 @@ void LoopVersioning::addPHINodes(
     // First see if we have a single-operand PHI with the value defined by the
     // original loop.
     for (auto I = PHIBlock->begin(); (PN = dyn_cast<PHINode>(I)); ++I) {
-      assert(PN->getNumOperands() == 1 &&
-             "Exit block should only have on predecessor");
-      if (PN->getIncomingValue(0) == Inst)
+      if (PN->getIncomingValue(0) == Inst) {
+        assert(PN->getNumOperands() == 1 &&
+               "Exit block should only have on predecessor");
         break;
+      }
     }
     // If not create it.
     if (!PN) {

diff --git a/test/Transforms/LoopVersioning/lcssa.ll b/test/Transforms/LoopVersioning/lcssa.ll
new file mode 100644 (file)
index 0000000..2cd4662
--- /dev/null
+++ b/test/Transforms/LoopVersioning/lcssa.ll
@@ -0,0 +1,35 @@
+; RUN: opt -basicaa -loop-versioning -S < %s | FileCheck %s
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @fill(i8** %ls1.20, i8** %ls2.21, i8* %cse3.22) {
+; CHECK: bb1.lver.check:
+; CHECK:   br i1 %memcheck.conflict, label %bb1.ph.lver.orig, label %bb1.ph
+bb1.ph:
+  %ls1.20.promoted = load i8*, i8** %ls1.20
+  %ls2.21.promoted = load i8*, i8** %ls2.21
+  br label %bb1
+
+bb1:
+  %_tmp302 = phi i8* [ %ls2.21.promoted, %bb1.ph ], [ %_tmp30, %bb1 ]
+  %_tmp281 = phi i8* [ %ls1.20.promoted, %bb1.ph ], [ %_tmp28, %bb1 ]
+  %_tmp14 = getelementptr i8, i8* %_tmp281, i16 -1
+  %_tmp15 = load i8, i8* %_tmp14
+  %add = add i8 %_tmp15, 1
+  store i8 %add, i8* %_tmp281
+  store i8 %add, i8* %_tmp302
+  %_tmp28 = getelementptr i8, i8* %_tmp281, i16 1
+  %_tmp30 = getelementptr i8, i8* %_tmp302, i16 1
+  br i1 false, label %bb1, label %bb3.loopexit
+
+bb3.loopexit:
+  %_tmp30.lcssa = phi i8* [ %_tmp30, %bb1 ]
+  %_tmp15.lcssa = phi i8 [ %_tmp15, %bb1 ]
+  %_tmp28.lcssa = phi i8* [ %_tmp28, %bb1 ]
+  store i8* %_tmp28.lcssa, i8** %ls1.20
+  store i8 %_tmp15.lcssa, i8* %cse3.22
+  store i8* %_tmp30.lcssa, i8** %ls2.21
+  br label %bb3
+
+bb3:
+  ret void
+}