SSAify invariant 2: every use dominated by its definition

SonicField · SonicField · commit cc4a18e7e5de · 2026-04-18T00:40:25.000-07:00
Complete 5/5 self-consistency invariants. Uses phx_dom_create/dominates
to verify domination property for all non-phi uses.
diff --git a/Python/jit/hir/ssaify_verify.cpp b/Python/jit/hir/ssaify_verify.cpp
@@ -7,11 +7,37 @@
 #include "cinderx/Jit/hir/ssaify_c.h"
 #include "cinderx/Jit/hir/hir_basic_block_c.h"
 #include "cinderx/Jit/hir/hir_instr_c.h"
+#include "cinderx/Jit/hir/dominator_c.h"
 #include "cinderx/Common/log.h"
 
 extern "C" void *hir_func_cfg(void *);
 extern "C" void *hir_reg_instr(void *);
 
+struct DomCtx {
+  PhxDominatorState *dom;
+  void *use_instr;
+  int ok;
+};
+
+static int check_use_dominated(void **reg_slot, void *ctx_raw) {
+  DomCtx *ctx = (DomCtx *)ctx_raw;
+  void *reg = *reg_slot;
+  if (!reg) return 1;
+  void *def_instr = hir_reg_instr(reg);
+  if (!def_instr) return 1;
+  HirBasicBlock *def_block = (HirBasicBlock *)hir_c_block(def_instr);
+  HirBasicBlock *use_block = (HirBasicBlock *)hir_c_block(ctx->use_instr);
+  if (!def_block || !use_block) return 1;
+  int def_id = hir_bb_id(def_block);
+  int use_id = hir_bb_id(use_block);
+  if (!phx_dom_dominates(ctx->dom, def_id, use_id)) {
+    JIT_LOG("SSAify verify FAIL: use not dominated by definition");
+    ctx->ok = 0;
+    return 0;
+  }
+  return 1;
+}
+
 extern "C" {
 
 int hir_ssaify_verify(void *func_handle) {
@@ -25,6 +51,9 @@ int hir_ssaify_verify(void *func_handle) {
     return 0;
   }
 
+  /* Build dominator tree for invariant 2 */
+  PhxDominatorState *dom = phx_dom_create(func_handle);
+
   for (HirBasicBlock *bb = hir_cfg_first_block(cfg); bb;
        bb = hir_cfg_next_block(cfg, bb)) {
     size_t num_preds = hir_bb_in_edges_count(bb);
@@ -37,6 +66,20 @@ int hir_ssaify_verify(void *func_handle) {
         void *def_instr = hir_reg_instr(output);
         if (def_instr != instr) {
           JIT_LOG("SSAify verify FAIL: register has wrong defining instr");
+          phx_dom_destroy(dom);
+          return 0;
+        }
+      }
+
+      /* Invariant 2: Every use dominated by its definition */
+      if (!hir_c_is_phi(instr)) {
+        DomCtx ctx;
+        ctx.dom = dom;
+        ctx.use_instr = instr;
+        ctx.ok = 1;
+        hir_c_visit_uses(instr, check_use_dominated, &ctx);
+        if (!ctx.ok) {
+          phx_dom_destroy(dom);
           return 0;
         }
       }
@@ -49,6 +92,7 @@ int hir_ssaify_verify(void *func_handle) {
           JIT_LOG(
               "SSAify verify FAIL: phi has {} operands but block has {} preds",
               num_ops, num_preds);
+          phx_dom_destroy(dom);
           return 0;
         }
 
@@ -61,6 +105,7 @@ int hir_ssaify_verify(void *func_handle) {
             HirBasicBlock *pred_j = (HirBasicBlock *)edge_j->from;
             if (pred_i == pred_j) {
               JIT_LOG("SSAify verify FAIL: duplicate predecessor in phi");
+              phx_dom_destroy(dom);
               return 0;
             }
           }
@@ -69,6 +114,7 @@ int hir_ssaify_verify(void *func_handle) {
     }
   }
 
+  phx_dom_destroy(dom);
   return 1;
 }
 
