Add CodeGen support for functions that always return arguments via a new parameter attribute 'returned', which is taken advantage of in target-independent tail call opportunity detection and in ARM call lowering (when placed on an integral first parameter).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179925 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 89 insertions, 0 deletions

diff --git a/test/CodeGen/X86/this-return-64.ll b/test/CodeGen/X86/this-return-64.ll
new file mode 100644
index 0000000000..2b26a89e3c
--- /dev/null
+++ b/test/CodeGen/X86/this-return-64.ll
@@ -0,0 +1,89 @@
+; RUN: llc < %s -mtriple=x86_64-pc-win32 | FileCheck %s
+
+%struct.A = type { i8 }
+%struct.B = type { i32 }
+%struct.C = type { %struct.B }
+%struct.D = type { %struct.B }
+%struct.E = type { %struct.B }
+
+declare %struct.A* @A_ctor(%struct.A* returned)
+declare %struct.B* @B_ctor(%struct.B* returned, i32)
+
+declare %struct.A* @A_ctor_nothisret(%struct.A*)
+declare %struct.B* @B_ctor_nothisret(%struct.B*, i32)
+
+define %struct.C* @C_ctor(%struct.C* %this, i32 %y) {
+entry:
+; CHECK: C_ctor:
+; CHECK: jmp     B_ctor                  # TAILCALL
+  %0 = getelementptr inbounds %struct.C* %this, i64 0, i32 0
+  %call = tail call %struct.B* @B_ctor(%struct.B* %0, i32 %y)
+  ret %struct.C* %this
+}
+
+define %struct.C* @C_ctor_nothisret(%struct.C* %this, i32 %y) {
+entry:
+; CHECK: C_ctor_nothisret:
+; CHECK-NOT: jmp     B_ctor_nothisret
+  %0 = getelementptr inbounds %struct.C* %this, i64 0, i32 0
+  %call = tail call %struct.B* @B_ctor_nothisret(%struct.B* %0, i32 %y)
+  ret %struct.C* %this
+}
+
+define %struct.D* @D_ctor(%struct.D* %this, i32 %y) {
+entry:
+; CHECK: D_ctor:
+; CHECK: movq    %rcx, [[SAVETHIS:%r[0-9a-z]+]]
+; CHECK: callq   A_ctor
+; CHECK: movq    [[SAVETHIS]], %rcx
+; CHECK: jmp     B_ctor                  # TAILCALL
+  %0 = bitcast %struct.D* %this to %struct.A*
+  %call = tail call %struct.A* @A_ctor(%struct.A* %0)
+  %1 = getelementptr inbounds %struct.D* %this, i64 0, i32 0
+  %call2 = tail call %struct.B* @B_ctor(%struct.B* %1, i32 %y)
+; (this next line would never be generated by Clang, actually)
+  %2 = bitcast %struct.A* %call to %struct.D*
+  ret %struct.D* %2
+}
+
+define %struct.D* @D_ctor_nothisret(%struct.D* %this, i32 %y) {
+entry:
+; CHECK: D_ctor_nothisret:
+; CHECK: movq    %rcx, [[SAVETHIS:%r[0-9a-z]+]]
+; CHECK: callq   A_ctor_nothisret
+; CHECK: movq    [[SAVETHIS]], %rcx
+; CHECK-NOT: jmp     B_ctor_nothisret
+  %0 = bitcast %struct.D* %this to %struct.A*
+  %call = tail call %struct.A* @A_ctor_nothisret(%struct.A* %0)
+  %1 = getelementptr inbounds %struct.D* %this, i64 0, i32 0
+  %call2 = tail call %struct.B* @B_ctor_nothisret(%struct.B* %1, i32 %y)
+; (this next line would never be generated by Clang, actually)
+  %2 = bitcast %struct.A* %call to %struct.D*
+  ret %struct.D* %2
+}
+
+define %struct.E* @E_ctor(%struct.E* %this, i32 %x) {
+entry:
+; CHECK: E_ctor:
+; CHECK: movq    %rcx, [[SAVETHIS:%r[0-9a-z]+]]
+; CHECK: callq   B_ctor
+; CHECK: movq    [[SAVETHIS]], %rcx
+; CHECK: jmp     B_ctor                  # TAILCALL
+  %b = getelementptr inbounds %struct.E* %this, i64 0, i32 0
+  %call = tail call %struct.B* @B_ctor(%struct.B* %b, i32 %x)
+  %call4 = tail call %struct.B* @B_ctor(%struct.B* %b, i32 %x)
+  ret %struct.E* %this
+}
+
+define %struct.E* @E_ctor_nothisret(%struct.E* %this, i32 %x) {
+entry:
+; CHECK: E_ctor_nothisret:
+; CHECK: movq    %rcx, [[SAVETHIS:%r[0-9a-z]+]]
+; CHECK: callq   B_ctor_nothisret
+; CHECK: movq    [[SAVETHIS]], %rcx
+; CHECK-NOT: jmp     B_ctor_nothisret
+  %b = getelementptr inbounds %struct.E* %this, i64 0, i32 0
+  %call = tail call %struct.B* @B_ctor_nothisret(%struct.B* %b, i32 %x)
+  %call4 = tail call %struct.B* @B_ctor_nothisret(%struct.B* %b, i32 %x)
+  ret %struct.E* %this
+}