[BitcodeReader] Ensure we can read constant vector selects with an i1 condition

[filcab]

Summary

Constant vectors weren't allowed to have an i1 condition in the
BitcodeReader. Make sure we have the same restrictions that are
documented, not more.

[kschimpf]

lib/Bitcode/Reader/BitcodeReader.cpp

2482

Out of curiosity, why not use SelectorTy instead of Type::getInt1Ty(Context), since you have already computed it?

[filcab]

True. I'll fix it later today.

Thanks,

Filipe

[filcab]

Addressed review comments.

lib/Bitcode/Reader/BitcodeReader.cpp

case bitc::CST_CODE_CE_GEP: {  // CE_GEP:        [n x operands]
       break;
     }
     case bitc::CST_CODE_CE_SELECT: {  // CE_SELECT: [opval#, opval#, opval#]
       if (Record.size() < 3)
         return error("Invalid record");
 
       Type *SelectorTy = Type::getInt1Ty(Context);
 
-      // If CurTy is a vector of length n, then Record[0] must be a <n x i1>
-      // vector. Otherwise, it must be a single bit.
+      // The selector might be an i1 or an <n x i1>
+      // Get the type from the ValueList before getting a forward ref.
       if (VectorType *VTy = dyn_cast<VectorType>(CurTy))
+        if (Value *V = ValueList[Record[0]])
+          if (SelectorTy != V->getType())
             SelectorTy = VectorType::get(Type::getInt1Ty(Context),
                                          VTy->getNumElements());
 
       V = ConstantExpr::getSelect(ValueList.getConstantFwdRef(Record[0],
                                                               SelectorTy),
                                   ValueList.getConstantFwdRef(Record[1],CurTy),
                                   ValueList.getConstantFwdRef(Record[2],CurTy));
       break;
     }
     case bitc::CST_CODE_CE_EXTRACTELT

test/Bitcode/select.ll

 ; RUN: llvm-as < %s | llvm-dis | FileCheck %s
 ; RUN: verify-uselistorder < %s
 
 define <2 x i32> @main() {
   ret <2 x i32> select (<2 x i1> <i1 false, i1 undef>, <2 x i32> zeroinitializer, <2 x i32> <i32 0, i32 undef>)
 }
 
 ; CHECK: define <2 x i32> @main() {
 ; CHECK:   ret <2 x i32> <i32 0, i32 undef>
 ; CHECK: }
+
+define <2 x float> @f() {
+  ret <2 x float> select (i1 ptrtoint (<2 x float> ()* @f to i1), <2 x float> <float 1.000000e+00, float 0.000000e+00>, <2 x float> zeroinitializer)
+}
+
+; CHECK: define <2 x float> @f() {
+; CHECK:   ret <2 x float> select (i1 ptrtoint (<2 x float> ()* @f to i1), <2 x float> <float 1.000000e+00, float 0.000000e+00>, <2 x float> zeroinitializer)
+; CHECK: }