Instrumented malloc and free with dummy functions.

tests_lit/asan_tests/instrumentmalloc.ll

+; Test that calls to malloc() and free() are replaced
+
+; REQUIRES: allow_dump
+
+; RUN: %p2i -i %s --args -verbose=inst -threads=0 -fsanitize-address \
+; RUN:     --allow-externally-defined-symbols | FileCheck --check-prefix=DUMP %s
+
+declare external i32 @malloc(i32)
+declare external void @free(i32)
+
+define internal void @func() {
+  %ptr = call i32 @malloc(i32 42)
+  call void @free(i32 %ptr)
+  ret void
+}
+
+; DUMP-LABEL: ================ Instrumented CFG ================
+; DUMP-NEXT: define internal void @func() {
+; DUMP-NEXT: __0:
+; DUMP-NEXT: %ptr = call i32 @__asan_malloc(i32 42)
+; DUMP-NEXT: call void @__asan_free(i32 %ptr)
+; DUMP-NEXT: ret void
+; DUMP-NEXT: }