SLPVectorizer: When sorting by domination for CSE don't assert on unreachable code.

There is no total ordering if the CFG is disconnected. We don't care if we
catch all CSE opportunities in dead code either so just exclude ignore them in
the assert.

PR19646

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208461 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 32 insertions, 1 deletions

diff --git a/lib/Transforms/Vectorize/SLPVectorizer.cpp b/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 0eb045e628..cecb18b918 100644
--- a/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -1827,7 +1827,8 @@ void BoUpSLP::optimizeGatherSequence() {
   for (SmallVectorImpl<BasicBlock *>::iterator I = CSEWorkList.begin(),
                                                E = CSEWorkList.end();
        I != E; ++I) {
-    assert((I == CSEWorkList.begin() || !DT->dominates(*I, *std::prev(I))) &&
+    assert((I == CSEWorkList.begin() || !DT->isReachableFromEntry(*I) ||
+            !DT->dominates(*I, *std::prev(I))) &&
            "Worklist not sorted properly!");
     BasicBlock *BB = *I;
     // For all instructions in blocks containing gather sequences:
diff --git a/test/Transforms/SLPVectorizer/X86/cse.ll b/test/Transforms/SLPVectorizer/X86/cse.ll
index bbfd6f28ea..d2ad7eb1a8 100644
--- a/test/Transforms/SLPVectorizer/X86/cse.ll
+++ b/test/Transforms/SLPVectorizer/X86/cse.ll
@@ -217,3 +217,33 @@ return:                                           ; preds = %entry, %if.end
   ret i32 0
 }
 
+%class.B.53.55 = type { %class.A.52.54, double }
+%class.A.52.54 = type { double, double, double }
+
+@a = external global double, align 8
+
+define void @PR19646(%class.B.53.55* %this) {
+entry:
+  br i1 undef, label %if.end13, label %if.end13
+
+sw.epilog7:                                       ; No predecessors!
+  %.in = getelementptr inbounds %class.B.53.55* %this, i64 0, i32 0, i32 1
+  %0 = load double* %.in, align 8
+  %add = fadd double undef, 0.000000e+00
+  %add6 = fadd double %add, %0
+  %1 = load double* @a, align 8
+  %add8 = fadd double %1, 0.000000e+00
+  %_dy = getelementptr inbounds %class.B.53.55* %this, i64 0, i32 0, i32 2
+  %2 = load double* %_dy, align 8
+  %add10 = fadd double %add8, %2
+  br i1 undef, label %if.then12, label %if.end13
+
+if.then12:                                        ; preds = %sw.epilog7
+  %3 = load double* undef, align 8
+  br label %if.end13
+
+if.end13:                                         ; preds = %if.then12, %sw.epilog7, %entry
+  %x.1 = phi double [ 0.000000e+00, %if.then12 ], [ %add6, %sw.epilog7 ], [ undef, %entry ], [ undef, %entry ]
+  %b.0 = phi double [ %3, %if.then12 ], [ %add10, %sw.epilog7 ], [ undef, %entry], [ undef, %entry ]
+  unreachable
+}