llvm/clang/test/CodeGen/assign.c

// RUN: %clang_cc1 -triple x86_64 -emit-llvm -o - %s | FileCheck %s

// Check that we don't generate unnecessary reloads.
//
// CHECK-LABEL: define{{.*}} void @f0()
// CHECK:      [[x_0:%.*]] = alloca i32, align 4
// CHECK-NEXT: [[y_0:%.*]] = alloca i32, align 4
// CHECK-NEXT: store i32 1, ptr [[x_0]]
// CHECK-NEXT: store i32 1, ptr [[x_0]]
// CHECK-NEXT: store i32 1, ptr [[y_0]]
// CHECK: }
void f0(void) {
  int x, y;
  x = 1;
  y = (x = 1);
}

// This used to test that we generate reloads for volatile access,
// but that does not appear to be correct behavior for C.
//
// CHECK-LABEL: define{{.*}} void @f1()
// CHECK:      [[x_1:%.*]] = alloca i32, align 4
// CHECK-NEXT: [[y_1:%.*]] = alloca i32, align 4
// CHECK-NEXT: store volatile i32 1, ptr [[x_1]]
// CHECK-NEXT: store volatile i32 1, ptr [[x_1]]
// CHECK-NEXT: store volatile i32 1, ptr [[y_1]]
// CHECK: }
void f1(void) {
  volatile int x, y;
  x = 1;
  y = (x = 1);
}