[PATCH] Correct extractelement constant folding

PaweĊ‚ Bylica chfast at gmail.com
Thu Apr 23 08:08:36 PDT 2015


Hi majnemer,

Constant folding of extractelement with out-of-bound index produces undef also for indexes bigger than 64bit (instead of crash assert failure as before)

http://reviews.llvm.org/D9225

Files:
  lib/IR/ConstantFold.cpp
  unittests/IR/ConstantsTest.cpp

Index: lib/IR/ConstantFold.cpp
===================================================================
--- lib/IR/ConstantFold.cpp
+++ lib/IR/ConstantFold.cpp
@@ -789,11 +789,10 @@
     return UndefValue::get(Val->getType()->getVectorElementType());
 
   if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
-    uint64_t Index = CIdx->getZExtValue();
     // ee({w,x,y,z}, wrong_value) -> undef
-    if (Index >= Val->getType()->getVectorNumElements())
+    if (CIdx->uge(Val->getType()->getVectorNumElements()))
       return UndefValue::get(Val->getType()->getVectorElementType());
-    return Val->getAggregateElement(Index);
+    return Val->getAggregateElement(CIdx->getZExtValue());
   }
   return nullptr;
 }
Index: unittests/IR/ConstantsTest.cpp
===================================================================
--- unittests/IR/ConstantsTest.cpp
+++ unittests/IR/ConstantsTest.cpp
@@ -187,6 +187,10 @@
   Constant *P6 = ConstantExpr::getBitCast(P4, VectorType::get(Int16Ty, 2));
 
   Constant *One = ConstantInt::get(Int32Ty, 1);
+  Constant *Two = ConstantInt::get(Int64Ty, 2);
+  Constant *Big = ConstantInt::get(getGlobalContext(),
+                                   APInt{256, uint64_t(-1), true});
+  Constant *Undef = UndefValue::get(Int64Ty);
 
   #define P0STR "ptrtoint (i32** @dummy to i32)"
   #define P1STR "uitofp (i32 ptrtoint (i32** @dummy to i32) to float)"
@@ -255,6 +259,10 @@
 
   CHECK(ConstantExpr::getExtractElement(P6, One), "extractelement <2 x i16> "
         P6STR ", i32 1");
+
+  EXPECT_TRUE(isa<UndefValue>(ConstantExpr::getExtractElement(P6, Two)));
+  EXPECT_TRUE(isa<UndefValue>(ConstantExpr::getExtractElement(P6, Big)));
+  EXPECT_TRUE(isa<UndefValue>(ConstantExpr::getExtractElement(P6, Undef)));
 }
 
 #ifdef GTEST_HAS_DEATH_TEST

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