[clang] [CIR] Upstream zero init for global variables (PR #133100)

[Bruno Cardoso Lopes via cfe-commits]

================
@@ -67,6 +67,40 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
     return create<cir::ConstantOp>(loc, attr.getType(), attr);
   }
 
+  mlir::TypedAttr getConstNullPtrAttr(mlir::Type t) {
+    assert(mlir::isa<cir::PointerType>(t) && "expected cir.ptr");
+    return getConstPtrAttr(t, 0);
+  }
+
+  mlir::TypedAttr getZeroAttr(mlir::Type t) {
+    return cir::ZeroAttr::get(getContext(), t);
+  }
+
+  mlir::TypedAttr getZeroInitAttr(mlir::Type ty) {
+    if (mlir::isa<cir::IntType>(ty))
+      return cir::IntAttr::get(ty, 0);
+    if (auto fltType = mlir::dyn_cast<cir::SingleType>(ty))
+      return cir::FPAttr::getZero(fltType);
+    if (auto fltType = mlir::dyn_cast<cir::DoubleType>(ty))
+      return cir::FPAttr::getZero(fltType);
+    if (auto fltType = mlir::dyn_cast<cir::LongDoubleType>(ty))
+      return cir::FPAttr::getZero(fltType);
+    if (auto fltType = mlir::dyn_cast<cir::FP16Type>(ty))
+      return cir::FPAttr::getZero(fltType);
+    if (auto fltType = mlir::dyn_cast<cir::FP128Type>(ty))
+      return cir::FPAttr::getZero(fltType);
+    if (auto fltType = mlir::dyn_cast<cir::BF16Type>(ty))
+      return cir::FPAttr::getZero(fltType);
+    if (auto arrTy = mlir::dyn_cast<cir::ArrayType>(ty))
+      return getZeroAttr(arrTy);
+    if (auto ptrTy = mlir::dyn_cast<cir::PointerType>(ty))
+      return getConstNullPtrAttr(ptrTy);
+    if (mlir::isa<cir::BoolType>(ty)) {
+      return getCIRBoolAttr(false);
+    }
+    llvm_unreachable("Zero initializer for given type is NYI");
+  }
----------------
bcardosolopes wrote:

Seems like all these 3 functions are a repetition from https://github.com/llvm/llvm-project/pull/132974, this is a bit confusing and requiring reviewing the same content more than once - might be better to wait until the dep lands or work on something without dependency

https://github.com/llvm/llvm-project/pull/133100