[clang] [CIR] Add support for array constructors (PR #149142)

[Andy Kaylor via cfe-commits]

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@@ -0,0 +1,70 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -Wno-unused-value -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s -check-prefix=CIR
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -Wno-unused-value -fclangir -emit-llvm %s -o %t-cir.ll
+// RUN: FileCheck --input-file=%t-cir.ll %s -check-prefix=LLVM
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -Wno-unused-value -emit-llvm %s -o %t.ll
+// RUN: FileCheck --input-file=%t.ll %s -check-prefix=OGCG
+
+struct S {
+    S();
+};
+
+void foo() {
+    S s[42];
+}
+
+// CIR: cir.func dso_local @_Z3foov()
+// CIR:   %[[ARRAY:.*]] = cir.alloca !cir.array<!rec_S x 42>, !cir.ptr<!cir.array<!rec_S x 42>>, ["s", init]
+// CIR:   %[[CONST42:.*]] = cir.const #cir.int<42> : !u64i
+// CIR:   %[[DECAY:.*]] = cir.cast(array_to_ptrdecay, %[[ARRAY]] : !cir.ptr<!cir.array<!rec_S x 42>>), !cir.ptr<!rec_S>
+// CIR:   %[[END_PTR:.*]] = cir.ptr_stride(%[[DECAY]] : !cir.ptr<!rec_S>, %[[CONST42]] : !u64i), !cir.ptr<!rec_S>
+// CIR:   %[[ITER:.*]] = cir.alloca !cir.ptr<!rec_S>, !cir.ptr<!cir.ptr<!rec_S>>, ["__array_idx"]
----------------
andykaylor wrote:

The alloca location determines when stack space is reserved and isn't generally concurrent with the lifetime of the variable. As a general rule, all allocas for the function are gathered at the top of the entry block, regardless of the scope of the variables they represent. Some targets aren't tolerant of allocas in the middle of a function. Classic codegen maintains a variable (AllocaInsertPt) in CodeGenFunction for this exact purpose. We don't seem to have one of those in CIR codegen yet.

https://github.com/llvm/llvm-project/pull/149142