Refactor cast<>'s in if conditionals, which can only assert on failure.

Summary:
This patch refactors several instances of cast<> used in if
conditionals.  Since cast<> asserts on failure, the else branch can
never be taken.

In some cases, the fix is to replace cast<> with dyn_cast<>.  While
others required the removal of the conditional and some minor
refactoring.

A discussion can be seen here: http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20190318/265044.html

Differential Revision: https://reviews.llvm.org/D59529

llvm-svn: 356441

2 files changed, 15 insertions, 26 deletions

diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index 102d21e5191..0772dcccc5a 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -1698,31 +1698,20 @@ ConstantLValueEmitter::tryEmitAbsolute(llvm::Type *destTy) {
   auto offset = getOffset();
 
   // If we're producing a pointer, this is easy.
-  if (auto destPtrTy = cast<llvm::PointerType>(destTy)) {
-    if (Value.isNullPointer()) {
-      // FIXME: integer offsets from non-zero null pointers.
-      return CGM.getNullPointer(destPtrTy, DestType);
-    }
-
-    // Convert the integer to a pointer-sized integer before converting it
-    // to a pointer.
-    // FIXME: signedness depends on the original integer type.
-    auto intptrTy = CGM.getDataLayout().getIntPtrType(destPtrTy);
-    llvm::Constant *C = offset;
-    C = llvm::ConstantExpr::getIntegerCast(getOffset(), intptrTy,
-                                           /*isSigned*/ false);
-    C = llvm::ConstantExpr::getIntToPtr(C, destPtrTy);
-    return C;
-  }
-
-  // Otherwise, we're basically returning an integer constant.
-
-  // FIXME: this does the wrong thing with ptrtoint of a null pointer,
-  // but since we don't know the original pointer type, there's not much
-  // we can do about it.
-
-  auto C = getOffset();
-  C = llvm::ConstantExpr::getIntegerCast(C, destTy, /*isSigned*/ false);
+  auto destPtrTy = cast<llvm::PointerType>(destTy);
+  if (Value.isNullPointer()) {
+    // FIXME: integer offsets from non-zero null pointers.
+    return CGM.getNullPointer(destPtrTy, DestType);
+  }
+
+  // Convert the integer to a pointer-sized integer before converting it
+  // to a pointer.
+  // FIXME: signedness depends on the original integer type.
+  auto intptrTy = CGM.getDataLayout().getIntPtrType(destPtrTy);
+  llvm::Constant *C = offset;
+  C = llvm::ConstantExpr::getIntegerCast(getOffset(), intptrTy,
+                                         /*isSigned*/ false);
+  C = llvm::ConstantExpr::getIntToPtr(C, destPtrTy);
   return C;
 }
 
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index cf6d0cf4483..7a5cdf6865f 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -735,7 +735,7 @@ public:
         CGM.CreateRuntimeFunction(FTy, "_CxxThrowException");
     // _CxxThrowException is stdcall on 32-bit x86 platforms.
     if (CGM.getTarget().getTriple().getArch() == llvm::Triple::x86) {
-      if (auto *Fn = cast<llvm::Function>(Throw.getCallee()))
+      if (auto *Fn = dyn_cast<llvm::Function>(Throw.getCallee()))
         Fn->setCallingConv(llvm::CallingConv::X86_StdCall);
     }
     return Throw;