Rewrite ConstStructBuilder with a mechanism that can cope with splitting and updating constants.

Summary:
This adds a ConstantBuilder class that deals with incrementally building
an aggregate constant, including support for overwriting
previously-emitted parts of the aggregate with new values.

This fixes a bunch of cases where we used to be unable to reduce a
DesignatedInitUpdateExpr down to an IR constant, and also lays some
groundwork for emission of class constants with [[no_unique_address]]
members.

Reviewers: rjmccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D63371

llvm-svn: 363620

1 files changed, 66 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/designated-init.cpp b/clang/test/CodeGenCXX/designated-init.cpp
new file mode 100644
index 00000000000..0b483296b4c
--- /dev/null
+++ b/clang/test/CodeGenCXX/designated-init.cpp
@@ -0,0 +1,66 @@
+// RUN: %clang_cc1 -std=c++98 -emit-llvm -o - %s -triple x86_64-linux-gnu | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 -emit-llvm -o - %s -triple x86_64-linux-gnu | FileCheck %s
+
+struct A { int x, y[3]; };
+struct B { A a; };
+
+// CHECK: @b = global %{{[^ ]*}} { %{{[^ ]*}} { i32 1, [3 x i32] [i32 2, i32 5, i32 4] } }
+B b = {(A){1, 2, 3, 4}, .a.y[1] = 5};
+
+union U {
+  int n;
+  float f;
+};
+struct C {
+  int x;
+  U u[3];
+};
+struct D {
+  C c;
+};
+
+// CHECK: @d1 = {{.*}} { i32 1, [3 x %[[U:.*]]] [%[[U]] { i32 2 }, %[[U]] { i32 5 }, %[[U]] { i32 4 }] }
+D d1 = {(C){1, {{.n=2}, {.f=3}, {.n=4}}}, .c.u[1].n = 5};
+
+// CHECK: @d2 = {{.*}} { i32 1, { %[[U]], float, %[[U]] } { %[[U]] { i32 2 }, float 5.{{0*}}e+00, %[[U]] { i32 4 } } }
+D d2 = {(C){1, 2, 3, 4}, .c.u[1].f = 5};
+
+struct Bitfield {
+  int a : 3;
+  int b : 4;
+  int c : 5;
+};
+struct WithBitfield {
+  int n;
+  Bitfield b;
+};
+// CHECK: @bitfield = {{.*}} { i32 1, { i8, i8, [2 x i8] } { i8 42, i8 2, [2 x i8] undef } }
+WithBitfield bitfield = {1, (Bitfield){2, 3, 4}, .b.b = 5};
+
+struct String {
+  const char buffer[12];
+};
+struct WithString {
+  String str;
+};
+// CHECK: @string = {{.*}} [12 x i8] c"Hello World\00" } }
+WithString string = {(String){"hello world"}, .str.buffer[0] = 'H', .str.buffer[6] = 'W'};
+
+struct LargeArray {
+  int arr[4096];
+};
+struct WithLargeArray {
+  LargeArray arr;
+};
+// CHECK: @large = global { { <{ [11 x i32], [4085 x i32] }> } } { { <{ [11 x i32], [4085 x i32] }> } { <{ [11 x i32], [4085 x i32] }> <{ [11 x i32] [i32 1, i32 2, i32 3, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 10], [4085 x i32] zeroinitializer }> } }
+WithLargeArray large = {(LargeArray){1, 2, 3}, .arr.arr[10] = 10};
+
+union OverwritePaddingWithBitfield {
+  struct Padding { unsigned : 8; char c; } padding;
+  char bitfield : 3;
+};
+struct WithOverwritePaddingWithBitfield {
+  OverwritePaddingWithBitfield a;
+};
+// CHECK: @overwrite_padding = global { { i8, i8 } } { { i8, i8 } { i8 3, i8 1 } }
+WithOverwritePaddingWithBitfield overwrite_padding = {(OverwritePaddingWithBitfield){1}, .a.bitfield = 3};