[llvm-commits] [llvm] r123963 - in /llvm/trunk: lib/Transforms/InstCombine/InstructionCombining.cpp test/Transforms/InstCombine/select.ll

[Nick Lewycky]

Author: nicholas
Date: Thu Jan 20 20:30:43 2011
New Revision: 123963

URL: http://llvm.org/viewvc/llvm-project?rev=123963&view=rev
Log:
Don't try to pull vector bitcasts that change the number of elements through
a select. A vector select is pairwise on each element so we'd need a new
condition with the right number of elements to select on. Fixes PR8994.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
    llvm/trunk/test/Transforms/InstCombine/select.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp?rev=123963&r1=123962&r2=123963&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Thu Jan 20 20:30:43 2011
@@ -455,8 +455,9 @@
 
 static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO,
                                              InstCombiner *IC) {
-  if (CastInst *CI = dyn_cast<CastInst>(&I))
+  if (CastInst *CI = dyn_cast<CastInst>(&I)) {
     return IC->Builder->CreateCast(CI->getOpcode(), SO, I.getType());
+  }
 
   // Figure out if the constant is the left or the right argument.
   bool ConstIsRHS = isa<Constant>(I.getOperand(1));
@@ -498,11 +499,24 @@
     // Bool selects with constant operands can be folded to logical ops.
     if (SI->getType()->isIntegerTy(1)) return 0;
 
+    // If it's a bitcast involving vectors, make sure it has the same number of
+    // elements on both sides.
+    if (BitCastInst *BC = dyn_cast<BitCastInst>(&Op)) {
+      const VectorType *DestTy = dyn_cast<VectorType>(BC->getDestTy());
+      const VectorType *SrcTy = dyn_cast<VectorType>(BC->getSrcTy());
+
+      // Verify that either both or neither are vectors.
+      if ((SrcTy == NULL) != (DestTy == NULL)) return 0;
+      // If vectors, verify that they have the same number of elements.
+      if (SrcTy && SrcTy->getNumElements() != DestTy->getNumElements())
+        return 0;
+    }
+    
     Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this);
     Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this);
 
-    return SelectInst::Create(SI->getCondition(), SelectTrueVal,
-                              SelectFalseVal);
+    return SelectInst::Create(SI->getCondition(),
+                              SelectTrueVal, SelectFalseVal);
   }
   return 0;
 }

Modified: llvm/trunk/test/Transforms/InstCombine/select.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/select.ll?rev=123963&r1=123962&r2=123963&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/select.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/select.ll Thu Jan 20 20:30:43 2011
@@ -689,3 +689,14 @@
 ; CHECK-NEXT: %min = select i1 %is_a_nonpositive, i64 %a_ext, i64 2
 ; CHECK-NEXT: ret i64 %min
 }
+
+; PR8994
+
+; Theis select instruction can't be eliminated because trying to do so would
+; change the number of vector elements. This used to assert.
+define i48 @test51(<3 x i1> %icmp, <3 x i16> %tmp) {
+  %select = select <3 x i1> %icmp, <3 x i16> zeroinitializer, <3 x i16> %tmp
+; CHECK: select <3 x i1>
+  %tmp2 = bitcast <3 x i16> %select to i48
+  ret i48 %tmp2
+}