TD DSGraphs for test.c at various optimization levels (for http://llvm.org/bugs/show_bug.cgi?id=15110).

O0-td.bar.dot.png

O0-td.main.dot.png

O0-test.ll

; ModuleID = 'test.c'
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%struct.foo = type { i32, float }

define %struct.foo* @bar(%struct.foo* %f) nounwind uwtable {
  %1 = alloca %struct.foo*, align 8
  %f2 = alloca %struct.foo*, align 8
  store %struct.foo* %f, %struct.foo** %1, align 8
  %2 = call i8* @malloc(i64 8)
  %3 = bitcast i8* %2 to %struct.foo*
  store %struct.foo* %3, %struct.foo** %f2, align 8
  %4 = load %struct.foo** %1, align 8
  %5 = getelementptr inbounds %struct.foo* %4, i32 0, i32 0
  %6 = load i32* %5, align 4
  %7 = load %struct.foo** %f2, align 8
  %8 = getelementptr inbounds %struct.foo* %7, i32 0, i32 0
  store i32 %6, i32* %8, align 4
  %9 = load %struct.foo** %1, align 8
  %10 = getelementptr inbounds %struct.foo* %9, i32 0, i32 1
  %11 = load float* %10, align 4
  %12 = load %struct.foo** %f2, align 8
  %13 = getelementptr inbounds %struct.foo* %12, i32 0, i32 1
  store float %11, float* %13, align 4
  %14 = load %struct.foo** %f2, align 8
  ret %struct.foo* %14
}

declare i8* @malloc(i64)

define i32 @main() nounwind uwtable {
  %1 = alloca i32, align 4
  %f = alloca %struct.foo*, align 8
  %f2 = alloca %struct.foo*, align 8
  store i32 0, i32* %1
  %2 = call i8* @malloc(i64 8)
  %3 = bitcast i8* %2 to %struct.foo*
  store %struct.foo* %3, %struct.foo** %f, align 8
  %4 = load %struct.foo** %f, align 8
  %5 = getelementptr inbounds %struct.foo* %4, i32 0, i32 0
  store i32 1, i32* %5, align 4
  %6 = load %struct.foo** %f, align 8
  %7 = getelementptr inbounds %struct.foo* %6, i32 0, i32 1
  store float 5.000000e-01, float* %7, align 4
  %8 = load %struct.foo** %f, align 8
  %9 = call %struct.foo* @bar(%struct.foo* %8)
  store %struct.foo* %9, %struct.foo** %f2, align 8
  %10 = load %struct.foo** %f, align 8
  %11 = call i32 (...)* @free(%struct.foo* %10)
  %12 = load %struct.foo** %f2, align 8
  %13 = call i32 (...)* @free(%struct.foo* %12)
  ret i32 0
}

declare i32 @free(...)

O1-td.bar.dot.png

O1-td.main.dot.png

O1-test.ll

; ModuleID = 'test.c'
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%struct.foo = type { i32, float }

define noalias %struct.foo* @bar(%struct.foo* nocapture %f) nounwind uwtable {
  %1 = tail call i8* @malloc(i64 8) nounwind
  %2 = bitcast i8* %1 to %struct.foo*
  %3 = getelementptr inbounds %struct.foo* %f, i64 0, i32 0
  %4 = load i32* %3, align 4, !tbaa !0
  %5 = bitcast i8* %1 to i32*
  store i32 %4, i32* %5, align 4, !tbaa !0
  %6 = getelementptr inbounds %struct.foo* %f, i64 0, i32 1
  %7 = load float* %6, align 4, !tbaa !3
  %8 = getelementptr inbounds i8* %1, i64 4
  %9 = bitcast i8* %8 to float*
  store float %7, float* %9, align 4, !tbaa !3
  ret %struct.foo* %2
}

declare noalias i8* @malloc(i64) nounwind

define i32 @main() nounwind uwtable {
  %1 = tail call i8* @malloc(i64 8) nounwind
  %2 = bitcast i8* %1 to %struct.foo*
  %3 = bitcast i8* %1 to i32*
  store i32 1, i32* %3, align 4, !tbaa !0
  %4 = getelementptr inbounds i8* %1, i64 4
  %5 = bitcast i8* %4 to float*
  store float 5.000000e-01, float* %5, align 4, !tbaa !3
  %6 = tail call %struct.foo* @bar(%struct.foo* %2)
  %7 = tail call i32 (...)* @free(i8* %1) nounwind
  %8 = tail call i32 (...)* @free(%struct.foo* %6) nounwind
  ret i32 0
}

declare i32 @free(...)

!0 = metadata !{metadata !"int", metadata !1}
!1 = metadata !{metadata !"omnipotent char", metadata !2}
!2 = metadata !{metadata !"Simple C/C++ TBAA"}
!3 = metadata !{metadata !"float", metadata !1}

O3-td.bar.dot.png

O3-td.main.dot.png

O3-test.ll

; ModuleID = 'test.c'
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%struct.foo = type { i32, float }

define noalias %struct.foo* @bar(%struct.foo* nocapture %f) nounwind uwtable {
  %1 = tail call i8* @malloc(i64 8) nounwind
  %2 = bitcast i8* %1 to %struct.foo*
  %3 = getelementptr inbounds %struct.foo* %f, i64 0, i32 0
  %4 = load i32* %3, align 4, !tbaa !0
  %5 = bitcast i8* %1 to i32*
  store i32 %4, i32* %5, align 4, !tbaa !0
  %6 = getelementptr inbounds %struct.foo* %f, i64 0, i32 1
  %7 = load float* %6, align 4, !tbaa !3
  %8 = getelementptr inbounds i8* %1, i64 4
  %9 = bitcast i8* %8 to float*
  store float %7, float* %9, align 4, !tbaa !3
  ret %struct.foo* %2
}

declare noalias i8* @malloc(i64) nounwind

define i32 @main() nounwind uwtable {
  %1 = tail call i8* @malloc(i64 8) nounwind
  %2 = bitcast i8* %1 to i32*
  store i32 1, i32* %2, align 4, !tbaa !0
  %3 = getelementptr inbounds i8* %1, i64 4
  %4 = bitcast i8* %3 to float*
  store float 5.000000e-01, float* %4, align 4, !tbaa !3
  %5 = tail call i8* @malloc(i64 8) nounwind
  %6 = bitcast i8* %5 to i32*
  store i32 1, i32* %6, align 4, !tbaa !0
  %7 = getelementptr inbounds i8* %5, i64 4
  %8 = bitcast i8* %7 to float*
  store float 5.000000e-01, float* %8, align 4, !tbaa !3
  %9 = tail call i32 (...)* @free(i8* %1) nounwind
  %10 = tail call i32 (...)* @free(i8* %5) nounwind
  ret i32 0
}

declare i32 @free(...)

!0 = metadata !{metadata !"int", metadata !1}
!1 = metadata !{metadata !"omnipotent char", metadata !2}
!2 = metadata !{metadata !"Simple C/C++ TBAA"}
!3 = metadata !{metadata !"float", metadata !1}

test.c

struct foo {
  int x;
  float y;
};

struct foo* bar(struct foo *f) {
  struct foo *f2 = (struct foo*) malloc(sizeof(struct foo));
  f2->x = f->x;
  f2->y = f->y;
  return f2;
}

int main() {
  struct foo *f = (struct foo*) malloc(sizeof(struct foo));
  f->x = 1;
  f->y = .5;
  struct foo *f2 = bar(f);
  free(f);
  free(f2);
  return 0;
}