Add a pass to lower is.constant and objectsize intrinsics

This pass lowers is.constant and objectsize intrinsics not simplified by
earlier constant folding, i.e. if the object given is not constant or if
not using the optimized pass chain. The result is recursively simplified
and constant conditionals are pruned, so that dead blocks are removed
even for -O0. This allows inline asm blocks with operand constraints to
work all the time.

The new pass replaces the existing lowering in the codegen-prepare pass
and fallbacks in SDAG/GlobalISEL and FastISel. The latter now assert
on the intrinsics.

Differential Revision: https://reviews.llvm.org/D65280

llvm-svn: 374743

1 files changed, 3 insertions, 21 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 3c36cc6f659..9a29a010c14 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -6388,29 +6388,11 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
     DAG.setRoot(Res);
     return;
   }
-  case Intrinsic::objectsize: {
-    // If we don't know by now, we're never going to know.
-    ConstantInt *CI = dyn_cast<ConstantInt>(I.getArgOperand(1));
-
-    assert(CI && "Non-constant type in __builtin_object_size?");
-
-    SDValue Arg = getValue(I.getCalledValue());
-    EVT Ty = Arg.getValueType();
-
-    if (CI->isZero())
-      Res = DAG.getConstant(-1ULL, sdl, Ty);
-    else
-      Res = DAG.getConstant(0, sdl, Ty);
-
-    setValue(&I, Res);
-    return;
-  }
+  case Intrinsic::objectsize:
+    llvm_unreachable("llvm.objectsize.* should have been lowered already");
 
   case Intrinsic::is_constant:
-    // If this wasn't constant-folded away by now, then it's not a
-    // constant.
-    setValue(&I, DAG.getConstant(0, sdl, MVT::i1));
-    return;
+    llvm_unreachable("llvm.is.constant.* should have been lowered already");
 
   case Intrinsic::annotation:
   case Intrinsic::ptr_annotation: