Apply SSA by command line option

Default: off.

.github/workflows/test.yml

@@ -26,6 +26,9 @@ jobs:
     - name: test xcc gen2
       run: make test-gen2
 
+    - name: test ssa
+      run: make -C tests clean && make XCC="../xcc --apply-ssa" -C tests cc-tests test-examples
+
     - name: setup
       run: |
         npm ci

src/_debug/dump_ir.c

@@ -356,11 +356,13 @@ int main(int argc, char *argv[]) {
   enum {
     OPT_KEEP_VIRTUAL_REGISTER = 128,
     OPT_KEEP_PHI,
+    OPT_SSA,
   };
 
   static const struct option options[] = {
     {"-keep-virtual", no_argument, OPT_KEEP_VIRTUAL_REGISTER},
     {"-keep-phi", no_argument, OPT_KEEP_PHI},
+    {"-apply-ssa", no_argument, OPT_SSA},
 
     {NULL},
   };
@@ -377,6 +379,13 @@ int main(int argc, char *argv[]) {
       keep_phi = true;
       break;
 
+    case OPT_SSA:
+      {
+        extern bool apply_ssa;
+        apply_ssa = true;
+      }
+      break;
+
     case '?':
       fprintf(stderr, "Warning: unknown option: %s\n", argv[optind - 1]);
       break;

src/cc/backend/optimize.c

@@ -12,6 +12,7 @@
 #include "util.h"
 
 bool keep_phi;
+bool apply_ssa;
 
 static IR *is_last_jmp(BB *bb) {
   int len;
@@ -542,11 +543,16 @@ void optimize(RegAlloc *ra, BBContainer *bbcon) {
     peephole(ra, bb);
   }
 
-  make_ssa(ra, bbcon);
-  copy_propagation(ra, bbcon);
-  remove_unused_vregs(ra, bbcon);
-  if (!keep_phi) {
-    resolve_phis(ra, bbcon);
+  if (apply_ssa) {
+    make_ssa(ra, bbcon);
+    copy_propagation(ra, bbcon);
+    remove_unused_vregs(ra, bbcon);
+    if (!keep_phi) {
+      resolve_phis(ra, bbcon);
+      remove_unnecessary_bb(bbcon);
+    }
+  } else {
+    remove_unused_vregs(ra, bbcon);
     remove_unnecessary_bb(bbcon);
   }
   detect_from_bbs(bbcon);

src/cc/cc1.c

@@ -11,6 +11,7 @@
 #include "emit_code.h"
 #include "fe_misc.h"
 #include "lexer.h"
+#include "optimize.h"  // opt_flags
 #include "parser.h"
 #include "type.h"
 #include "util.h"
@@ -70,6 +71,7 @@ static bool parse_fopt(const char *optarg, bool value) {
 int main(int argc, char *argv[]) {
   enum {
     OPT_FNO = 128,
+    OPT_SSA,
   };
 
   static const struct option options[] = {
@@ -82,6 +84,9 @@ int main(int argc, char *argv[]) {
     {"f", required_argument},
     {"W", required_argument},
 
+    // Feature flag.
+    {"-apply-ssa", no_argument, OPT_SSA},
+
     {NULL},
   };
   int opt;
@@ -130,6 +135,13 @@ int main(int argc, char *argv[]) {
       }
       break;
 
+    case OPT_SSA:
+      {
+        extern bool apply_ssa;
+        apply_ssa = true;
+      }
+      break;
+
     case '?':
       fprintf(stderr, "Warning: unknown option: %s\n", argv[optind - 1]);
       break;

src/xcc/main.c

@@ -303,6 +303,8 @@ static void parse_options(int argc, char *argv[], Options *opts) {
     OPT_PEDANTIC,
     OPT_MMD,
     OPT_NO_PIE,
+
+    OPT_SSA,
   };
 
   static const struct option kOptions[] = {
@@ -340,6 +342,9 @@ static void parse_options(int argc, char *argv[], Options *opts) {
     {"MMD", no_argument, OPT_MMD},
     {"no-pie", no_argument, OPT_NO_PIE},
 
+    // Feature flag.
+    {"-apply-ssa", no_argument, OPT_SSA},
+
     {NULL},
   };
 
@@ -503,6 +508,10 @@ static void parse_options(int argc, char *argv[], Options *opts) {
       // Silently ignored.
       vec_push(opts->linker_options, argv[optind - 1]);
       break;
+
+    case OPT_SSA:
+      vec_push(opts->cc1_cmd, argv[optind - 1]);
+      break;
     }
   }
 }