[llvm] r182199 - LoopVectorize: Handle single edge PHIs

[Arnold Schwaighofer]

Author: arnolds
Date: Sat May 18 13:38:34 2013
New Revision: 182199

URL: http://llvm.org/viewvc/llvm-project?rev=182199&view=rev
Log:
LoopVectorize: Handle single edge PHIs

We might encouter single edge PHIs - handle them with an identity select.

Fixes PR15990.

Modified:
    llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
    llvm/trunk/test/Transforms/LoopVectorize/if-conv-crash.ll

Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=182199&r1=182198&r2=182199&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Sat May 18 13:38:34 2013
@@ -2105,7 +2105,6 @@ InnerLoopVectorizer::vectorizeBlockInLoo
         // optimizations will clean it up.
 
         unsigned NumIncoming = P->getNumIncomingValues();
-        assert(NumIncoming > 1 && "Invalid PHI");
 
         // Generate a sequence of selects of the form:
         // SELECT(Mask3, In3,
@@ -2117,10 +2116,11 @@ InnerLoopVectorizer::vectorizeBlockInLoo
           VectorParts &In0 = getVectorValue(P->getIncomingValue(In));
 
           for (unsigned part = 0; part < UF; ++part) {
-            // We don't need to 'select' the first PHI operand because it is
-            // the default value if all of the other masks don't match.
+            // We might have single edge PHIs (blocks) - use an identity
+            // 'select' for the first PHI operand.
             if (In == 0)
-              Entry[part] = In0[part];
+              Entry[part] = Builder.CreateSelect(Cond[part], In0[part],
+                                                 In0[part]);
             else
               // Select between the current value and the previous incoming edge
               // based on the incoming mask.

Modified: llvm/trunk/test/Transforms/LoopVectorize/if-conv-crash.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/if-conv-crash.ll?rev=182199&r1=182198&r2=182199&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/if-conv-crash.ll (original)
+++ llvm/trunk/test/Transforms/LoopVectorize/if-conv-crash.ll Sat May 18 13:38:34 2013
@@ -37,3 +37,25 @@ if.end21:
 if.end25:                                         ; preds = %entry
   ret void
 }
+
+; PR15990
+; We can have basic blocks with single entry PHI nodes.
+define void @single_entry_phi(i32* %a, i32 *%b) {
+entry:
+  br label %for.cond1.preheader
+
+for.cond1.preheader:
+  %inc10 = phi i32 [ 0, %entry ], [ %inc, %for.end ]
+  br label %for.end
+
+for.end:
+  %malicious.phi = phi i32 [ 0, %for.cond1.preheader ]
+  %inc = add nsw i32 %inc10, 1
+  %tobool = icmp eq i32 %inc, 0
+  br i1 %tobool, label %for.cond.for.end5, label %for.cond1.preheader
+
+for.cond.for.end5:
+  %and.lcssa = phi i32 [ %malicious.phi, %for.end ]
+  store i32 %and.lcssa, i32* %a, align 4
+  ret void
+}