[CodeGen] Initialize large arrays by copying from a global

Currently, clang compiles explicit initializers for array
elements into series of store instructions. For large arrays of
built-in types this results in bloated output code and
significant amount of time spent on the instruction selection
phase. This patch fixes the issue by initializing such arrays
with global constants that store the binary image of the
initializer.

Differential Revision: https://reviews.llvm.org/D43181

llvm-svn: 325478

1 files changed, 18 insertions, 5 deletions

diff --git a/clang/test/CodeGen/init.c b/clang/test/CodeGen/init.c
index 5d086723cc0..9924662cddf 100644
--- a/clang/test/CodeGen/init.c
+++ b/clang/test/CodeGen/init.c
@@ -8,8 +8,9 @@ unsigned v2[2][3] = {[0 ... 1][0 ... 1] = 2222, 3333};
 // CHECK-DAG: %struct.M = type { [2 x %struct.I] }
 // CHECK-DAG: %struct.I = type { [3 x i32] }
 
-// CHECK: [1 x %struct.M] [%struct.M { [2 x %struct.I] [%struct.I { [3 x i32] [i32 4, i32 4, i32 0] }, %struct.I { [3 x i32] [i32 4, i32 4, i32 5] }] }],
-// CHECK: [2 x [3 x i32]] {{[[][[]}}3 x i32] [i32 2222, i32 2222, i32 0], [3 x i32] [i32 2222, i32 2222, i32 3333]],
+// CHECK-DAG: [1 x %struct.M] [%struct.M { [2 x %struct.I] [%struct.I { [3 x i32] [i32 4, i32 4, i32 0] }, %struct.I { [3 x i32] [i32 4, i32 4, i32 5] }] }],
+// CHECK-DAG: [2 x [3 x i32]] {{[[][[]}}3 x i32] [i32 2222, i32 2222, i32 0], [3 x i32] [i32 2222, i32 2222, i32 3333]],
+// CHECK-DAG: [[INIT14:.*]] = private global [16 x i32] [i32 0, i32 0, i32 0, i32 0, i32 0, i32 17, i32 17, i32 17, i32 17, i32 17, i32 17, i32 17, i32 0, i32 0, i32 0, i32 0], align 4
 
 void f1() {
   // Scalars in braces.
@@ -33,8 +34,8 @@ void f3() {
 }
 
 // Constants
-// CHECK: @g3 = constant i32 10
-// CHECK: @f4.g4 = internal constant i32 12
+// CHECK-DAG: @g3 = constant i32 10
+// CHECK-DAG: @f4.g4 = internal constant i32 12
 const int g3 = 10;
 int f4() {
   static const int g4 = 12;
@@ -61,7 +62,7 @@ void f6() {
 
 
 
-// CHECK: @test7 = global{{.*}}{ i32 0, [4 x i8] c"bar\00" }
+// CHECK-DAG: @test7 = global{{.*}}{ i32 0, [4 x i8] c"bar\00" }
 // PR8217
 struct a7 {
   int  b;
@@ -151,3 +152,15 @@ void PR20473() {
   // CHECK: memcpy{{.*}}getelementptr inbounds ([3 x i8], [3 x i8]* @
   bar((char[3]) {""});
 }
+
+// Test that we initialize large member arrays by copying from a global and not
+// with a series of stores.
+struct S14 { int a[16]; };
+
+void test14(struct S14 *s14) {
+// CHECK-LABEL: @test14
+// CHECK: call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 {{.*}}, i8* align 4 {{.*}} [[INIT14]] {{.*}}, i32 64, i1 false)
+// CHECK-NOT: store
+// CHECK: ret void
+  *s14 = (struct S14) { { [5 ... 11] = 17 } };
+}