[PATCH] D13219: [InstCombine] SimplifyDemandedVectorElts wrongly analyzes ConstantVector select masks with ConstantExpr elements (PR24922).

[Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL249390: [InstCombine] Teach SimplifyDemandedVectorElts how to handle ConstantVector… (authored by adibiagio).

Changed prior to commit:
  http://reviews.llvm.org/D13219?vs=35880&id=36609#toc

Repository:
  rL LLVM

http://reviews.llvm.org/D13219

Files:
  llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
  llvm/trunk/test/Transforms/InstCombine/vec_demanded_elts.ll

Index: llvm/trunk/test/Transforms/InstCombine/vec_demanded_elts.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/vec_demanded_elts.ll
+++ llvm/trunk/test/Transforms/InstCombine/vec_demanded_elts.ll
@@ -253,3 +253,16 @@
   %a = tail call <4 x double> @llvm.x86.avx.vpermilvar.pd.256(<4 x double> %v, <4 x i64> zeroinitializer)
   ret <4 x double> %a
 }
+
+define <2 x i64> @PR24922(<2 x i64> %v) {
+; CHECK-LABEL: @PR24922
+; CHECK: select <2 x i1> 
+;
+; Check that instcombine doesn't wrongly fold the select statement into a
+; ret <2 x i64> %v
+;
+; FIXME: We should be able to simplify the ConstantExpr in the select mask.
+entry:
+  %result = select <2 x i1> <i1 icmp eq (i64 extractelement (<2 x i64> bitcast (<4 x i32> <i32 15, i32 15, i32 15, i32 15> to <2 x i64>), i64 0), i64 0), i1 true>, <2 x i64> %v, <2 x i64> zeroinitializer
+  ret <2 x i64> %result
+}
Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -1057,7 +1057,13 @@
     APInt LeftDemanded(DemandedElts), RightDemanded(DemandedElts);
     if (ConstantVector* CV = dyn_cast<ConstantVector>(I->getOperand(0))) {
       for (unsigned i = 0; i < VWidth; i++) {
-        if (CV->getAggregateElement(i)->isNullValue())
+        Constant *CElt = CV->getAggregateElement(i);
+        // Method isNullValue always returns false when called on a
+        // ConstantExpr. If CElt is a ConstantExpr then skip it in order to
+        // to avoid propagating incorrect information.
+        if (isa<ConstantExpr>(CElt))
+          continue;
+        if (CElt->isNullValue())
           LeftDemanded.clearBit(i);
         else
           RightDemanded.clearBit(i);


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