tcg: Build ffi data structures for helpers

Add libffi as a build requirement for TCI.
Add libffi to the dockerfiles to satisfy that requirement.

Construct an ffi_cif structure for each unique typemask.
Record the result in a separate hash table for later lookup;
this allows helper_table to stay const.

Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 65 insertions, 1 deletions

diff --git a/tcg/meson.build b/tcg/meson.build
index 5be3915..c4c63b1 100644
--- a/tcg/meson.build
+++ b/tcg/meson.build
@@ -9,6 +9,12 @@ tcg_ss.add(files(
   'tcg-op-gvec.c',
   'tcg-op-vec.c',
 ))
-tcg_ss.add(when: 'CONFIG_TCG_INTERPRETER', if_true: files('tci.c'))
+
+if get_option('tcg_interpreter')
+  libffi = dependency('libffi', version: '>=3.0', required: true,
+                      method: 'pkg-config', kwargs: static_kwargs)
+  specific_ss.add(libffi)
+  specific_ss.add(files('tci.c'))
+endif
 
 specific_ss.add_all(when: 'CONFIG_TCG', if_true: tcg_ss)
diff --git a/tcg/tcg.c b/tcg/tcg.c
index 8f4f171..de1a593 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -60,6 +60,10 @@
 #include "exec/log.h"
 #include "tcg-internal.h"
 
+#ifdef CONFIG_TCG_INTERPRETER
+#include <ffi.h>
+#endif
+
 /* Forward declarations for functions declared in tcg-target.c.inc and
    used here. */
 static void tcg_target_init(TCGContext *s);
@@ -539,6 +543,19 @@ static const TCGHelperInfo all_helpers[] = {
 };
 static GHashTable *helper_table;
 
+#ifdef CONFIG_TCG_INTERPRETER
+static GHashTable *ffi_table;
+
+static ffi_type * const typecode_to_ffi[8] = {
+    [dh_typecode_void] = &ffi_type_void,
+    [dh_typecode_i32]  = &ffi_type_uint32,
+    [dh_typecode_s32]  = &ffi_type_sint32,
+    [dh_typecode_i64]  = &ffi_type_uint64,
+    [dh_typecode_s64]  = &ffi_type_sint64,
+    [dh_typecode_ptr]  = &ffi_type_pointer,
+};
+#endif
+
 static int indirect_reg_alloc_order[ARRAY_SIZE(tcg_target_reg_alloc_order)];
 static void process_op_defs(TCGContext *s);
 static TCGTemp *tcg_global_reg_new_internal(TCGContext *s, TCGType type,
@@ -582,6 +599,47 @@ static void tcg_context_init(unsigned max_cpus)
                             (gpointer)&all_helpers[i]);
     }
 
+#ifdef CONFIG_TCG_INTERPRETER
+    /* g_direct_hash/equal for direct comparisons on uint32_t.  */
+    ffi_table = g_hash_table_new(NULL, NULL);
+    for (i = 0; i < ARRAY_SIZE(all_helpers); ++i) {
+        struct {
+            ffi_cif cif;
+            ffi_type *args[];
+        } *ca;
+        uint32_t typemask = all_helpers[i].typemask;
+        gpointer hash = (gpointer)(uintptr_t)typemask;
+        ffi_status status;
+        int nargs;
+
+        if (g_hash_table_lookup(ffi_table, hash)) {
+            continue;
+        }
+
+        /* Ignoring the return type, find the last non-zero field. */
+        nargs = 32 - clz32(typemask >> 3);
+        nargs = DIV_ROUND_UP(nargs, 3);
+
+        ca = g_malloc0(sizeof(*ca) + nargs * sizeof(ffi_type *));
+        ca->cif.rtype = typecode_to_ffi[typemask & 7];
+        ca->cif.nargs = nargs;
+
+        if (nargs != 0) {
+            ca->cif.arg_types = ca->args;
+            for (i = 0; i < nargs; ++i) {
+                int typecode = extract32(typemask, (i + 1) * 3, 3);
+                ca->args[i] = typecode_to_ffi[typecode];
+            }
+        }
+
+        status = ffi_prep_cif(&ca->cif, FFI_DEFAULT_ABI, nargs,
+                              ca->cif.rtype, ca->cif.arg_types);
+        assert(status == FFI_OK);
+
+        g_hash_table_insert(ffi_table, hash, (gpointer)&ca->cif);
+    }
+#endif
+
     tcg_target_init(s);
     process_op_defs(s);