Use 32-bits pointers to C code

On a 64-bit machine, we only need 32 bits to store a pointer to
the C code that implements a BEAM instruction. Refactor the code
to only use the lower 32 bits of each instruction word, and take
care to preserve the high 32 bits.

1 files changed, 33 insertions, 0 deletions

diff --git a/erts/configure.in b/erts/configure.in
index 85e167b93b..508e99a415 100644
--- a/erts/configure.in
+++ b/erts/configure.in
@@ -3774,6 +3774,39 @@ dnl
 LM_FIND_EMU_CC
 
 dnl
+dnl Test whether code pointers are always short (32 bits).
+dnl
+
+AC_MSG_CHECKING([whether the code model is small])
+saved_LDFLAGS="$LDFLAGS"
+LDFLAGS="$LDFLAGS $HIPEBEAMLDFLAGS"
+AC_TRY_RUN([
+   #include <stdlib.h>
+   int main() {
+    if ((unsigned long long)&main < (1ull << 32)) {
+       exit(0);
+    }
+    exit(1);
+   }
+],
+erl_code_model_small=yes,
+erl_code_model_small=no,
+erl_code_model_small=no)
+AC_MSG_RESULT([$erl_code_model_small])
+LDFLAGS="$saved_LDFLAGS"
+case $erl_code_model_small in
+     yes)
+        AC_DEFINE(CODE_MODEL_SMALL,[1],
+	[Define if the code model is small (code fits below 2Gb)])
+	CODE_MODEL=small
+	;;
+     no)
+	CODE_MODEL=unknown
+        ;;
+esac
+AC_SUBST(CODE_MODEL)
+
+dnl
 dnl DTrace & LTTNG
 dnl
 case $DYNAMIC_TRACE_FRAMEWORK in