clang/test/CodeGen/aarch64-byval-temp.c

   1 // RUN: %clang_cc1 -emit-llvm -triple arm64-- -o - %s -O0 | FileCheck %s --check-prefix=CHECK-O0
   2 // RUN: %clang_cc1 -emit-llvm -disable-llvm-optzns -triple arm64-- -o - %s -O3 | FileCheck %s --check-prefix=CHECK-O3
   3
   4 struct large {
   5     void* pointers[8];
   6 };
   7
   8 void pass_large(struct large);
   9
  10 // For arm64, we don't use byval to pass structs but instead we create
  11 // temporary allocas.
  12 //
  13 // Make sure we generate the appropriate lifetime markers for the temporary
  14 // allocas so that the optimizer can re-use stack slots if possible.
  15 void example(void) {
  16     struct large l = {0};
  17     pass_large(l);
  18     pass_large(l);
  19 }
  20 // CHECK-O0-LABEL: define{{.*}} void @example(
  21 // The alloca for the struct on the stack.
  22 // CHECK-O0: %[[l:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
  23 // The alloca for the temporary stack space that we use to pass the argument.
  24 // CHECK-O0-NEXT: %[[byvaltemp:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
  25 // Another one to pass the argument to the second function call.
  26 // CHECK-O0-NEXT: %[[byvaltemp1:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
  27 // First, memset `l` to 0.
  28 // CHECK-O0-NEXT: call void @llvm.memset.p0.i64(ptr align 8 %[[l]], i8 0, i64 64, i1 false)
  29 // Then, memcpy `l` to the temporary stack space.
  30 // CHECK-O0-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 8 %[[byvaltemp]], ptr align 8 %[[l]], i64 64, i1 false)
  31 // Finally, call using a pointer to the temporary stack space.
  32 // CHECK-O0-NEXT: call void @pass_large(ptr noundef %[[byvaltemp]])
  33 // Now, do the same for the second call, using the second temporary alloca.
  34 // CHECK-O0-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 8 %[[byvaltemp1]], ptr align 8 %[[l]], i64 64, i1 false)
  35 // CHECK-O0-NEXT: call void @pass_large(ptr noundef %[[byvaltemp1]])
  36 // CHECK-O0-NEXT: ret void
  37 //
  38 // At O3, we should have lifetime markers to help the optimizer re-use the temporary allocas.
  39 //
  40 // CHECK-O3-LABEL: define{{.*}} void @example(
  41 // The alloca for the struct on the stack.
  42 // CHECK-O3: %[[l:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
  43 // The alloca for the temporary stack space that we use to pass the argument.
  44 // CHECK-O3-NEXT: %[[byvaltemp:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
  45 // Another one to pass the argument to the second function call.
  46 // CHECK-O3-NEXT: %[[byvaltemp1:[0-9A-Za-z-]+]] = alloca %struct.large, align 8
  47 //
  48 // Mark the start of the lifetime for `l`
  49 // CHECK-O3-NEXT: call void @llvm.lifetime.start.p0(i64 64, ptr %[[l]])
  50 //
  51 // First, memset `l` to 0.
  52 // CHECK-O3-NEXT: call void @llvm.memset.p0.i64(ptr align 8 %[[l]], i8 0, i64 64, i1 false)
  53 //
  54 // Lifetime of the first temporary starts here and ends right after the call.
  55 // CHECK-O3-NEXT: call void @llvm.lifetime.start.p0(i64 64, ptr %[[byvaltemp]])
  56 //
  57 // Then, memcpy `l` to the temporary stack space.
  58 // CHECK-O3-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 8 %[[byvaltemp]], ptr align 8 %[[l]], i64 64, i1 false)
  59 // Finally, call using a pointer to the temporary stack space.
  60 // CHECK-O3-NEXT: call void @pass_large(ptr noundef %[[byvaltemp]])
  61 //
  62 // The lifetime of the temporary used to pass a pointer to the struct ends here.
  63 // CHECK-O3-NEXT: call void @llvm.lifetime.end.p0(i64 64, ptr %[[byvaltemp]])
  64 //
  65 // Now, do the same for the second call, using the second temporary alloca.
  66 // CHECK-O3-NEXT: call void @llvm.lifetime.start.p0(i64 64, ptr %[[byvaltemp1]])
  67 // CHECK-O3-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 8 %[[byvaltemp1]], ptr align 8 %[[l]], i64 64, i1 false)
  68 // CHECK-O3-NEXT: call void @pass_large(ptr noundef %[[byvaltemp1]])
  69 // CHECK-O3-NEXT: call void @llvm.lifetime.end.p0(i64 64, ptr %[[byvaltemp1]])
  70 //
  71 // Mark the end of the lifetime of `l`.
  72 // CHECK-O3-NEXT: call void @llvm.lifetime.end.p0(i64 64, ptr %l)
  73 // CHECK-O3-NEXT: ret void