now that we have CGT around, we can start using preferred types

for return values too.  Instead of compiling something like:

struct foo {
  int *X;
  float *Y;
};

struct foo test(struct foo *P) { return *P; }

to:

%1 = type { i64, i64 }

define %1 @test(%struct.foo* %P) nounwind {
entry:
  %retval = alloca %struct.foo, align 8           ; <%struct.foo*> [#uses=2]
  %P.addr = alloca %struct.foo*, align 8          ; <%struct.foo**> [#uses=2]
  store %struct.foo* %P, %struct.foo** %P.addr
  %tmp = load %struct.foo** %P.addr               ; <%struct.foo*> [#uses=1]
  %tmp1 = bitcast %struct.foo* %retval to i8*     ; <i8*> [#uses=1]
  %tmp2 = bitcast %struct.foo* %tmp to i8*        ; <i8*> [#uses=1]
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %tmp1, i8* %tmp2, i64 16, i32 8, i1 false)
  %0 = bitcast %struct.foo* %retval to %1*        ; <%1*> [#uses=1]
  %1 = load %1* %0, align 1                       ; <%1> [#uses=1]
  ret %1 %1
}

We now get the result more type safe, with:

define %struct.foo @test(%struct.foo* %P) nounwind {
entry:
  %retval = alloca %struct.foo, align 8           ; <%struct.foo*> [#uses=2]
  %P.addr = alloca %struct.foo*, align 8          ; <%struct.foo**> [#uses=2]
  store %struct.foo* %P, %struct.foo** %P.addr
  %tmp = load %struct.foo** %P.addr               ; <%struct.foo*> [#uses=1]
  %tmp1 = bitcast %struct.foo* %retval to i8*     ; <i8*> [#uses=1]
  %tmp2 = bitcast %struct.foo* %tmp to i8*        ; <i8*> [#uses=1]
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %tmp1, i8* %tmp2, i64 16, i32 8, i1 false)
  %0 = load %struct.foo* %retval                  ; <%struct.foo> [#uses=1]
  ret %struct.foo %0
}

That memcpy is completely terrible, but I don't know how to fix it.

llvm-svn: 109729