[InstSimplify] Support constant folding to vector of pointers

ConstantFolding crashes when trying to InstSimplify the following load:

@a = private unnamed_addr constant %mst {
     i8* inttoptr (i64 -1 to i8*),
     i8* inttoptr (i64 -1 to i8*)
}, align 8

%x = load <2 x i8*>* bitcast (%mst* @a to <2 x i8*>*), align 8

This patch fix this by adding support to this type of folding:

%x = load <2 x i8*>* bitcast (%mst* @a to <2 x i8*>*), align 8
==> gets folded to:
  %x = <2 x i8*> <i8* inttoptr (i64 -1 to i8*), i8* inttoptr (i64 -1 to i8*)>

llvm-svn: 220380

1 files changed, 12 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 3441ec3..cd25acb 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -55,7 +55,8 @@ static Constant *FoldBitCast(Constant *C, Type *DestTy,
   // Catch the obvious splat cases.
   if (C->isNullValue() && !DestTy->isX86_MMXTy())
     return Constant::getNullValue(DestTy);
-  if (C->isAllOnesValue() && !DestTy->isX86_MMXTy())
+  if (C->isAllOnesValue() && !DestTy->isX86_MMXTy() &&
+      !DestTy->isPtrOrPtrVectorTy()) // Don't get ones for ptr types!
     return Constant::getAllOnesValue(DestTy);
 
   // Handle a vector->integer cast.
@@ -197,7 +198,7 @@ static Constant *FoldBitCast(Constant *C, Type *DestTy,
 
   // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
   unsigned Ratio = NumDstElt/NumSrcElt;
-  unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
+  unsigned DstBitSize = TD.getTypeSizeInBits(DstEltTy);
 
   // Loop over each source value, expanding into multiple results.
   for (unsigned i = 0; i != NumSrcElt; ++i) {
@@ -213,6 +214,15 @@ static Constant *FoldBitCast(Constant *C, Type *DestTy,
                                   ConstantInt::get(Src->getType(), ShiftAmt));
       ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
 
+      // Truncate the element to an integer with the same pointer size and
+      // convert the element back to a pointer using a inttoptr.
+      if (DstEltTy->isPointerTy()) {
+        IntegerType *DstIntTy = Type::getIntNTy(C->getContext(), DstBitSize);
+        Constant *CE = ConstantExpr::getTrunc(Elt, DstIntTy);
+        Result.push_back(ConstantExpr::getIntToPtr(CE, DstEltTy));
+        continue;
+      }
+
       // Truncate and remember this piece.
       Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
     }