[InstCombine][SSE4a] Fix assertion failure caused by unsafe dyn_casts on the operands of extrq/extrqi intrinsic calls.

This patch fixes an assertion failure caused by unsafe dynamic casts on the
constant operands of sse4a intrinsic calls to extrq/extrqi

The combine logic that simplifies sse4a extrq/extrqi intrinsic calls currently
checks if the input operands are constants. Internally, that logic relies on
dyn_casts of values returned by calls to method Constant::getAggregateElement.
However, method getAggregateElemet may return nullptr if the constant element
cannot be retrieved. So, all the dyn_casts can potentially fail. This is what
happens for example if a constexpr value is passed in input to an extrq/extrqi
intrinsic call.

This patch fixes the problem by using a dyn_cast_or_null (instead of a simple
dyn_cast) on the result of each call to Constant::getAggregateElement.

Added reproducible test cases to x86-sse4a.ll.

Differential Revision: https://reviews.llvm.org/D24256

llvm-svn: 280804

1 files changed, 3 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 15069e62a73..eb334442988 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -584,7 +584,7 @@ static Value *simplifyX86extrq(IntrinsicInst &II, Value *Op0,
   // See if we're dealing with constant values.
   Constant *C0 = dyn_cast<Constant>(Op0);
   ConstantInt *CI0 =
-      C0 ? dyn_cast<ConstantInt>(C0->getAggregateElement((unsigned)0))
+      C0 ? dyn_cast_or_null<ConstantInt>(C0->getAggregateElement((unsigned)0))
          : nullptr;
 
   // Attempt to constant fold.
@@ -1856,10 +1856,10 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
     // See if we're dealing with constant values.
     Constant *C1 = dyn_cast<Constant>(Op1);
     ConstantInt *CILength =
-        C1 ? dyn_cast<ConstantInt>(C1->getAggregateElement((unsigned)0))
+        C1 ? dyn_cast_or_null<ConstantInt>(C1->getAggregateElement((unsigned)0))
            : nullptr;
     ConstantInt *CIIndex =
-        C1 ? dyn_cast<ConstantInt>(C1->getAggregateElement((unsigned)1))
+        C1 ? dyn_cast_or_null<ConstantInt>(C1->getAggregateElement((unsigned)1))
            : nullptr;
 
     // Attempt to simplify to a constant, shuffle vector or EXTRQI call.