Emit lifetime.start / lifetime.end markers for unnamed temporary objects.

This will give more information to the optimizers so that they can reuse stack slots.

llvm-svn: 213576

1 files changed, 132 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/unnamed-object-lifetime.cpp b/clang/test/CodeGenCXX/unnamed-object-lifetime.cpp
new file mode 100644
index 00000000000..c1422bc507c
--- /dev/null
+++ b/clang/test/CodeGenCXX/unnamed-object-lifetime.cpp
@@ -0,0 +1,132 @@
+// RUN: %clang_cc1 -triple i386-unknown-unknown -emit-llvm -O1 -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple i386-unknown-unknown -emit-llvm -O1 -fcxx-exceptions -fexceptions -o - %s | FileCheck --check-prefix=CHECK-EH %s
+
+// Test lifetime marker generation for unnamed temporary objects.
+
+struct X {
+  X();
+  ~X();
+  char t[33]; // make the class big enough so that lifetime markers get inserted
+};
+
+extern void useX(const X &);
+
+// CHECK-LABEL: define void @_Z6simplev
+// CHECK-EH-LABEL: define void @_Z6simplev
+void simple() {
+  // CHECK: [[ALLOCA:%.*]] = alloca %struct.X
+  // CHECK: [[PTR:%.*]] = getelementptr inbounds %struct.X* [[ALLOCA]], i32 0, i32 0, i32 0
+  // CHECK: call void @llvm.lifetime.start(i64 33, i8* [[PTR]])
+  // CHECK-NEXT: call void @_ZN1XC1Ev
+  // CHECK-NEXT: call void @_Z4useXRK1X
+  // CHECK-NEXT: call void @_ZN1XD1Ev
+  // CHECK-NEXT: call void @llvm.lifetime.end(i64 33, i8* [[PTR]])
+  //
+  // CHECK-EH: [[ALLOCA:%.*]] = alloca %struct.X
+  // CHECK-EH: [[PTR:%.*]] = getelementptr inbounds %struct.X* [[ALLOCA]], i32 0, i32 0, i32 0
+  // CHECK-EH: call void @llvm.lifetime.start(i64 33, i8* [[PTR]])
+  // CHECK-EH-NEXT: call void @_ZN1XC1Ev
+  // CHECK-EH: invoke void @_Z4useXRK1X
+  // CHECK-EH: invoke void @_ZN1XD1Ev
+  // CHECK-EH: call void @llvm.lifetime.end(i64 33, i8* [[PTR]])
+  // CHECK-EH: call void @llvm.lifetime.end(i64 33, i8* [[PTR]])
+  useX(X());
+}
+
+struct Y {
+  Y(){}
+  ~Y(){}
+  char t[34]; // make the class big enough so that lifetime markers get inserted
+};
+
+extern void useY(const Y &);
+
+// Check lifetime markers are inserted, despite Y's trivial constructor & destructor
+// CHECK-LABEL: define void @_Z7trivialv
+// CHECK-EH-LABEL: define void @_Z7trivialv
+void trivial() {
+  // CHECK: [[ALLOCA:%.*]] = alloca %struct.Y
+  // CHECK: [[PTR:%.*]] = getelementptr inbounds %struct.Y* [[ALLOCA]], i32 0, i32 0, i32 0
+  // CHECK: call void @llvm.lifetime.start(i64 34, i8* [[PTR]])
+  // CHECK-NEXT: call void @_Z4useYRK1Y
+  // CHECK-NEXT: call void @llvm.lifetime.end(i64 34, i8* [[PTR]])
+  //
+  // CHECK-EH: [[ALLOCA:%.*]] = alloca %struct.Y
+  // CHECK-EH: [[PTR:%.*]] = getelementptr inbounds %struct.Y* [[ALLOCA]], i32 0, i32 0, i32 0
+  // CHECK-EH: call void @llvm.lifetime.start(i64 34, i8* [[PTR]])
+  // CHECK-EH-NEXT: invoke void @_Z4useYRK1Y
+  // CHECK-EH: call void @llvm.lifetime.end(i64 34, i8* [[PTR]])
+  // CHECK-EH: call void @llvm.lifetime.end(i64 34, i8* [[PTR]])
+  useY(Y());
+}
+
+struct Z {
+  Z();
+  ~Z();
+  char t;
+};
+
+extern void useZ(const Z &);
+
+// Check lifetime markers are not inserted if the unnamed object is too small
+// CHECK-LABEL: define void @_Z8tooSmallv
+// CHECK-EH-LABEL: define void @_Z8tooSmallv
+void tooSmall() {
+  // CHECK-NOT: call void @llvm.lifetime.start
+  // CHECK: call void @_Z4useZRK1Z
+  // CHECK-NOT: call void @llvm.lifetime.end
+  // CHECK: ret
+  //
+  // CHECK-EH-NOT: call void @llvm.lifetime.start
+  // CHECK-EH: invoke void @_Z4useZRK1Z
+  // CHECK-EH-NOT: call void @llvm.lifetime.end
+  // CHECK-EH: ret
+  useZ(Z());
+}
+
+// Check the lifetime are inserted at the right place in their respective scope
+// CHECK-LABEL: define void @_Z6scopesv
+void scopes() {
+  // CHECK: alloca %struct
+  // CHECK: alloca %struct
+  // CHECK: call void @llvm.lifetime.start(i64 33, i8* [[X:%.*]])
+  // CHECK: call void @llvm.lifetime.end(i64 33, i8* [[X]])
+  // CHECK: call void @llvm.lifetime.start(i64 34, i8* [[Y:%.*]])
+  // CHECK: call void @llvm.lifetime.end(i64 34, i8* [[Y]])
+  useX(X());
+  useY(Y());
+}
+
+struct L {
+  L(int);
+  ~L();
+  char t[33];
+};
+
+// Check the lifetime-extended case
+// CHECK-LABEL: define void @_Z16extendedLifetimev
+void extendedLifetime() {
+  extern void useL(const L&);
+
+  // CHECK: [[A:%.*]] = alloca %struct.L
+  // CHECK: [[P:%.*]] = getelementptr inbounds %struct.L* [[A]], i32 0, i32 0, i32 0
+  // CHECK: call void @llvm.lifetime.start(i64 33, i8* [[P]])
+  // CHECK: call void @_ZN1LC1Ei(%struct.L* [[A]], i32 2)
+  // CHECK-NOT: call void @llvm.lifetime.end(i64 33, i8* [[P]])
+  // CHECK: call void @_Z4useLRK1L(%struct.L* dereferenceable(33) [[A]])
+  // CHECK: call void @_ZN1LD1Ev(%struct.L* [[A]])
+  // CHECK-NEXT: call void @llvm.lifetime.end(i64 33, i8* [[P]])
+  //
+  // CHECK-EH: [[A:%.*]] = alloca %struct.L
+  // CHECK-EH: [[P:%.*]] = getelementptr inbounds %struct.L* [[A]], i32 0, i32 0, i32 0
+  // CHECK-EH: call void @llvm.lifetime.start(i64 33, i8* [[P]])
+  // CHECK-EH: call void @_ZN1LC1Ei(%struct.L* [[A]], i32 2)
+  // CHECK-EH-NOT: call void @llvm.lifetime.end(i64 33, i8* [[P]])
+  // CHECK-EH: invoke void @_Z4useLRK1L(%struct.L* dereferenceable(33) [[A]])
+  // CHECK-EH: invoke void @_ZN1LD1Ev(%struct.L* [[A]])
+  // CHECK-EH: call void @llvm.lifetime.end(i64 33, i8* [[P]])
+  // CHECK-EH: invoke void @_ZN1LD1Ev(%struct.L* [[A]])
+  // CHECK-EH: call void @llvm.lifetime.end(i64 33, i8* [[P]])
+  const L &l = 2;
+  useL(l);
+}