Add a constant folding of casts from zero to zero. Fixes PR9011!

While here, I'd like to complain about how vector is not an aggregate type
according to llvm::Type::isAggregateType(), but they're listed under aggregate
types in the LangRef and zero vectors are stored as ConstantAggregateZero.

llvm-svn: 123956

2 files changed, 39 insertions, 0 deletions

diff --git a/llvm/lib/VMCore/ConstantFold.cpp b/llvm/lib/VMCore/ConstantFold.cpp
index a21b4a28e47..3fea1910ffe 100644
--- a/llvm/lib/VMCore/ConstantFold.cpp
+++ b/llvm/lib/VMCore/ConstantFold.cpp
@@ -511,10 +511,14 @@ Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
       return Constant::getNullValue(DestTy);
     return UndefValue::get(DestTy);
   }
+
   // No compile-time operations on this type yet.
   if (V->getType()->isPPC_FP128Ty() || DestTy->isPPC_FP128Ty())
     return 0;
 
+  if (V->isNullValue() && !DestTy->isX86_MMXTy())
+    return Constant::getNullValue(DestTy);
+
   // If the cast operand is a constant expression, there's a few things we can
   // do to try to simplify it.
   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
diff --git a/llvm/test/Transforms/ConstProp/constant-expr.ll b/llvm/test/Transforms/ConstProp/constant-expr.ll
index 556ed1f652a..33ed1a53c3e 100644
--- a/llvm/test/Transforms/ConstProp/constant-expr.ll
+++ b/llvm/test/Transforms/ConstProp/constant-expr.ll
@@ -65,3 +65,38 @@
 
 ; No check line. This used to crash llvm-as.
 @T6 = global <2 x i1> fcmp ole (<2 x float> fdiv (<2 x float> undef, <2 x float> <float 1.000000e+00, float 1.000000e+00>), <2 x float> zeroinitializer)
+
+
+; PR9011
+
+@pr9011_1 = constant <4 x i32> zext (<4 x i8> zeroinitializer to <4 x i32>)
+; CHECK: pr9011_1 = constant <4 x i32> zeroinitializer
+@pr9011_2 = constant <4 x i32> sext (<4 x i8> zeroinitializer to <4 x i32>)
+; CHECK: pr9011_2 = constant <4 x i32> zeroinitializer
+@pr9011_3 = constant <4 x i32> bitcast (<16 x i8> zeroinitializer to <4 x i32>)
+; CHECK: pr9011_3 = constant <4 x i32> zeroinitializer
+@pr9011_4 = constant <4 x float> uitofp (<4 x i8> zeroinitializer to <4 x float>)
+; CHECK: pr9011_4 = constant <4 x float> zeroinitializer
+@pr9011_5 = constant <4 x float> sitofp (<4 x i8> zeroinitializer to <4 x float>)
+; CHECK: pr9011_5 = constant <4 x float> zeroinitializer
+@pr9011_6 = constant <4 x i32> fptosi (<4 x float> zeroinitializer to <4 x i32>)
+; CHECK: pr9011_6 = constant <4 x i32> zeroinitializer
+@pr9011_7 = constant <4 x i32> fptoui (<4 x float> zeroinitializer to <4 x i32>)
+; CHECK: pr9011_7 = constant <4 x i32> zeroinitializer
+@pr9011_8 = constant <4 x float> fptrunc (<4 x double> zeroinitializer to <4 x float>)
+; CHECK: pr9011_8 = constant <4 x float> zeroinitializer
+@pr9011_9 = constant <4 x double> fpext (<4 x float> zeroinitializer to <4 x double>)
+; CHECK: pr9011_9 = constant <4 x double> zeroinitializer
+
+@pr9011_10 = constant <4 x double> bitcast (i256 0 to <4 x double>)
+; CHECK: pr9011_10 = constant <4 x double> zeroinitializer
+@pr9011_11 = constant <4 x float> bitcast (i128 0 to <4 x float>)
+; CHECK: pr9011_11 = constant <4 x float> zeroinitializer
+@pr9011_12 = constant <4 x i32> bitcast (i128 0 to <4 x i32>)
+; CHECK: pr9011_12 = constant <4 x i32> zeroinitializer
+@pr9011_13 = constant i256 bitcast (<4 x double> zeroinitializer to i256)
+; CHECK: pr9011_13 = constant i256 0
+@pr9011_14 = constant i128 bitcast (<4 x float> zeroinitializer to i128)
+; CHECK: pr9011_14 = constant i128 0
+@pr9011_15 = constant i128 bitcast (<4 x i32> zeroinitializer to i128)
+; CHECK: pr9011_15 = constant i128 0