From: Michael Beck <beck@ipd.info.uni-karlsruhe.de>
Date: Thu, 6 Jul 2006 16:27:01 +0000 (+0000)
Subject: add code to detect pure function
X-Git-Url: http://nsz.repo.hu/git/?a=commitdiff_plain;h=ac2f8f95a4996b57e7bbb1a2496202d2b9c49fc6;p=libfirm

add code to detect pure function
currently do not unpin calls to const functions

[r8012]
---

diff --git a/ir/opt/funccall.c b/ir/opt/funccall.c
index 38e5028ce..d2f152af6 100644
--- a/ir/opt/funccall.c
+++ b/ir/opt/funccall.c
@@ -25,23 +25,21 @@
 typedef struct _env_t {
   int  n_calls_removed_SymConst;
   int  n_calls_removed_Sel;
-  ir_node *list;                  /**< The list of all Calls that will be changed. */
-  ir_node *proj_list;             /**< list of all potential Proj nones that must be fixed.*/
+  ir_node *const_call_list;       /**< The list of all const function calls that will be changed. */
+  ir_node *pure_call_list;        /**< The list of all pure function calls that will be changed. */
+  ir_node *proj_list;             /**< The list of all potential Proj nodes that must be fixed. */
 } env_t;
 
 /**
- * remove memory from const function calls by rerouting
- * it's ProjM and connection the call with a NoMem node.
- *
- * Note: By "const function" we understand a function that did neither
- * read nor write memory. Hence its result depends solely on its
- * arguments.
+ * Collect all calls to const and pure functions
+ * to lists. Collect of Proj nodes into a Proj list.
  */
-static void rem_mem_from_const_fkt_calls(ir_node *node, void *env)
+static void collect_calls(ir_node *node, void *env)
 {
   env_t *ctx = env;
   ir_node *call, *ptr;
   entity *ent;
+  unsigned mode;
 
   if (get_irn_op(node) == op_Call) {
     call = node;
@@ -51,26 +49,31 @@ static void rem_mem_from_const_fkt_calls(ir_node *node, void *env)
     if (get_irn_op(ptr) == op_SymConst && get_SymConst_kind(ptr) == symconst_addr_ent) {
       ent = get_SymConst_entity(ptr);
 
-      if ((get_entity_additional_properties(ent) & mtp_property_const) == 0)
+      mode = get_entity_additional_properties(ent);
+      if (mode & (mtp_property_const|mtp_property_pure) == 0)
         return;
       ++ctx->n_calls_removed_SymConst;
     }
     else if (is_Sel(ptr) &&
 	     get_irg_callee_info_state(current_ir_graph) == irg_callee_info_consistent) {
-      /* If all possible callees are real functions, we can remove the memory edge. */
+      /* If all possible callees are const functions, we can remove the memory edge. */
       int i, n_callees = get_Call_n_callees(call);
       if (n_callees == 0)
         /* This is kind of strange:  dying code or a Call that will raise an exception
 	         when executed as there is no implementation to call.  So better not
 	         optimize. */
         return;
+
+      /* note that const function are a subset of pure ones */
+      mode = mtp_property_const | mtp_property_pure;
       for (i = 0; i < n_callees; ++i) {
         ent = get_Call_callee(call, i);
         if (ent == unknown_entity) {
           /* we don't know which entity is called here */
           return;
         }
-        if ((get_entity_additional_properties(ent) & mtp_property_const) == 0)
+        mode &= get_entity_additional_properties(ent);
+        if (mode == 0)
           return;
       }
       ++ctx->n_calls_removed_Sel;
@@ -78,9 +81,15 @@ static void rem_mem_from_const_fkt_calls(ir_node *node, void *env)
     else
       return;
 
-    /* ok, if we get here we found a call to a const function */
-    set_irn_link(call, ctx->list);
-    ctx->list = call;
+    /* ok, if we get here we found a call to a const or a pure function */
+    if (mode & mtp_property_pure) {
+      set_irn_link(call, ctx->pure_call_list);
+      ctx->pure_call_list = call;
+    }
+    else {
+      set_irn_link(call, ctx->const_call_list);
+      ctx->const_call_list = call;
+    }
   }
   else if (get_irn_op(node) == op_Proj) {
     /*
@@ -99,7 +108,7 @@ static void rem_mem_from_const_fkt_calls(ir_node *node, void *env)
       ctx->proj_list = node;
       break;
     default:
-      ;
+      break;
     }
   }
 }  /* rem_mem_from_const_fkt_calls */
@@ -111,7 +120,7 @@ static void rem_mem_from_const_fkt_calls(ir_node *node, void *env)
  * @param call_list  the list of all call sites of pure functions
  * @param proj_list  the list of all memory/exception Projs of this call sites
  */
-static void fix_call_list(ir_graph *irg, ir_node *call_list, ir_node *proj_list) {
+static void fix_const_call_list(ir_graph *irg, ir_node *call_list, ir_node *proj_list) {
   ir_node *call, *next, *mem, *proj;
   int exc_changed = 0;
 
@@ -175,106 +184,332 @@ static void fix_call_list(ir_graph *irg, ir_node *call_list, ir_node *proj_list)
   }
 }  /* fix_call_list */
 
-/*
- * optimize function calls by handling const functions
+
+/**
+ * Check if a graph represents a const function.
+ *
+ * @param irg  the graph
  */
-void optimize_funccalls(int force_run)
+static int is_const_function(ir_graph *irg)
 {
-  int i, j;
-  int change;
-  unsigned num_pure = 0;
+  ir_node *end, *endbl;
+  int j, change;
 
-  if (! get_opt_real_function_call())
-    return;
+  if (get_irg_additional_properties(irg) & mtp_property_const) {
+    /* already marked as a const function */
+    return 0;
+  }
 
-  /* first step: detect, which functions are const, i.e. do NOT touch any memory */
-  for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
-    ir_graph *irg  = get_irp_irg(i);
-    ir_node *end   = get_irg_end(irg);
-    ir_node *endbl = get_nodes_block(end);
+  end   = get_irg_end(irg);
+  endbl = get_nodes_block(end);
+  change = 0;
 
-    change = 0;
+  /* visit every Return */
+  for (j = get_Block_n_cfgpreds(endbl) - 1; j >= 0; --j) {
+    ir_node *node = get_Block_cfgpred(endbl, j);
+    ir_op   *op   = get_irn_op(node);
+    ir_node *mem;
 
-    if (get_irg_additional_properties(irg) & mtp_property_const) {
-      /* already marked as a const function */
-      ++num_pure;
+    /* Bad nodes usually do NOT produce anything, so it's ok */
+    if (op == op_Bad)
+      continue;
+
+    if (op == op_Return) {
+      mem = get_Return_mem(node);
+
+      /* Bad nodes usually do NOT produce anything, so it's ok */
+      if (is_Bad(mem))
+        continue;
+
+      change = mem != get_irg_initial_mem(irg);
+      if (change)
+        break;
     }
     else {
-      /* visit every Return */
-      for (j = get_Block_n_cfgpreds(endbl) - 1; j >= 0; --j) {
-        ir_node *node = get_Block_cfgpred(endbl, j);
-        ir_op   *op   = get_irn_op(node);
-        ir_node *mem;
-
-        /* Bad nodes usually do NOT produce anything, so it's ok */
-        if (op == op_Bad)
-          continue;
-
-        if (op == op_Return) {
-          mem = get_Return_mem(node);
-
-          /* Bad nodes usually do NOT produce anything, so it's ok */
-          if (is_Bad(mem))
-            continue;
-
-          change = mem != get_irg_initial_mem(irg);
-          if (change)
-            break;
-        }
-        else {
-          /* exception found */
-          change = 1;
-          break;
-        }
+      /* exception found */
+      change = 1;
+      break;
+    }
+  }
+
+  if (! change) {
+    /* check, if a keep-alive exists */
+    for (j = get_End_n_keepalives(end) - 1; j >= 0; --j) {
+      ir_node *mem = get_End_keepalive(end, j);
+
+      if (mode_M != get_irn_mode(mem))
+        continue;
+
+      change = mem != get_irg_initial_mem(irg);
+      if (change)
+        break;
+    }
+  }
+
+  if (! change) {
+    /* no memory changes found, it's a const function */
+    set_irg_additional_property(irg, mtp_property_const);
+    return 1;
+  }
+  return 0;
+}  /* is_const_function */
+
+/* a marker */
+static char _mark;
+#define MARK &_mark
+
+#define UNMARK_IRG(irg)     set_irg_link((irg), NULL)
+#define MARK_IRG(irg)       set_irg_link((irg), MARK)
+#define IS_IRG_MARKED(irg)  (get_irg_link(irg) == MARK)
+
+/* forward */
+static int is_pure_function(ir_graph *irg);
+
+#define UMAX(a,b) (a) > (b) ? (a) : (b)
+
+/**
+ * Follow the memory chain starting at node and determine
+ * the mtp_property.
+ *
+ * @return mtp_property_const if only calls of const functions are detected
+ *         mtp_property_pure if only Loads and const/pure
+ *         calls detected
+ *         bad_property else
+ */
+static unsigned _follow_mem(ir_node *node) {
+  unsigned m, mode = mtp_property_const;
+  ir_node  *ptr;
+  int i;
+
+  for (;;) {
+    if (irn_visited(node))
+      return mode;
+
+    mark_irn_visited(node);
+
+    switch (get_irn_opcode(node)) {
+    case iro_Proj:
+      node = get_Proj_pred(node);
+      break;
+
+    case iro_NoMem:
+      /* finish here */
+      return mode;
+
+    case iro_Phi:
+    case iro_Sync:
+      for (i = get_irn_arity(node) - 1; i >= 0; --i) {
+        mode &= _follow_mem(get_irn_n(node, i));
       }
+      break;
 
-      if (! change) {
-        /* check, if a keep-alive exists */
-        for (j = get_End_n_keepalives(end) - 1; j >= 0; --j) {
-          ir_node *mem = get_End_keepalive(end, j);
+    case iro_Load:
+      /* Beware volatile Loads are NOT allowed in pure functions */
+      if (get_Load_volatility(node) == volatility_is_volatile)
+        return 0;
+      mode = mtp_property_pure;
+      node = get_Load_mem(node);
+      break;
 
-          if (mode_M != get_irn_mode(mem))
-            continue;
+    case iro_Call:
+      /* a call is only tolerable if its either constant or pure */
+      ptr = get_Call_ptr(node);
+      if (get_irn_op(ptr) == op_SymConst &&
+          get_SymConst_kind(ptr) == symconst_addr_ent) {
+        entity   *ent = get_SymConst_entity(ptr);
+        ir_graph *irg = get_entity_irg(ent);
 
-          change = mem != get_irg_initial_mem(irg);
-          if (change)
-            break;
+        if (irg == current_ir_graph) {
+          /* A recursive call. The did not mode depend on this call */
+        }
+        else if (irg == NULL) {
+          m = get_entity_additional_properties(ent) & (mtp_property_const|mtp_property_pure);
+          if (! m)
+            return 0;
+          mode = UMAX(mode, m);
+        }
+        else if (irg != NULL) {
+          /* we have a graph. Check if it is already analyzed */
+          if (IS_IRG_MARKED(irg))
+            (void)is_pure_function(irg);
+
+          m = get_irg_additional_properties(irg) & (mtp_property_const|mtp_property_pure);
+          if (! m)
+            return 0;
+          mode = UMAX(mode, m);
         }
       }
+      else
+        return 0;
+      node = get_Call_mem(node);
+      break;
 
-      if (! change) {
-        /* no memory changes found, it's a const function */
-        set_irg_additional_property(irg, mtp_property_const);
-        ++num_pure;
-      }
+    default:
+      return 0;
     }
   }
+}  /* follow_mem */
 
-  if (force_run || num_pure > 0) {
-    env_t ctx;
+/**
+ * Follow the memory chain starting at node and determine
+ * the mtp_property.
+ *
+ * @return mtp_property_const if only calls of const functions are detected
+ *         mtp_property_pure if only Loads and const/pure
+ *         calls detected
+ *         0 else
+ */
+static unsigned follow_mem(ir_graph *irg, ir_node *node, unsigned mode) {
+  unsigned m;
+
+  inc_irg_visited(irg);
+  /* mark the initial mem: recursion stops here */
+  mark_irn_visited(get_irg_initial_mem(irg));
+  m = _follow_mem(node);
+  if (! m)
+    return 0;
+  return UMAX(mode, m);
+}  /* follow_mwm */
+
+/*
+ * Check if a graph represents a pure function.
+ *
+ * @param irg  the graph
+ */
+static int is_pure_function(ir_graph *irg) {
+  ir_node *end, *endbl;
+  int j;
+  unsigned mode = get_irg_additional_properties(irg);
+  ir_graph *rem = current_ir_graph;
+
+  if (mode & mtp_property_const) {
+    /* already marked as a const function */
+    return mtp_property_const;
+  }
+  if (mode & mtp_property_pure) {
+    /* already marked as a pure function */
+    return mtp_property_const;
+  }
 
-    ctx.n_calls_removed_SymConst = 0;
-    ctx.n_calls_removed_Sel = 0;
+  if (! IS_IRG_MARKED(irg))
+    return 0;
+  UNMARK_IRG(irg);
 
-    /* all calls of pure functions can be transformed into FuncCalls */
-    for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
-      ir_graph *irg  = get_irp_irg(i);
+  end   = get_irg_end(irg);
+  endbl = get_nodes_block(end);
+  mode  = mtp_property_const;
 
-      /* no need to do this on const functions */
-      if ((get_irg_additional_properties(irg) & mtp_property_const) == 0) {
-        ctx.list      = NULL;
-        ctx.proj_list = NULL;
-        irg_walk_graph(irg, NULL, rem_mem_from_const_fkt_calls, &ctx);
+  current_ir_graph = irg;
 
-        if (ctx.list)
-          fix_call_list(irg, ctx.list, ctx.proj_list);
-      }
+  /* visit every Return */
+  for (j = get_Block_n_cfgpreds(endbl) - 1; j >= 0; --j) {
+    ir_node *node = get_Block_cfgpred(endbl, j);
+    ir_op   *op   = get_irn_op(node);
+    ir_node *mem;
+
+    /* Bad nodes usually do NOT produce anything, so it's ok */
+    if (op == op_Bad)
+      continue;
+
+    if (op == op_Return) {
+      mem = get_Return_mem(node);
+
+      /* Bad nodes usually do NOT produce anything, so it's ok */
+      if (is_Bad(mem))
+        continue;
+
+      if (mem != get_irg_initial_mem(irg))
+        mode = follow_mem(irg, mem, mode);
+    }
+    else {
+      /* exception found. */
+      mode = follow_mem(irg, mem, mode);
+      break;
+    }
+    if (mode == 0)
+      break;
+  }
+
+  if (mode != 0) {
+    /* check, if a keep-alive exists */
+    for (j = get_End_n_keepalives(end) - 1; j >= 0; --j) {
+      ir_node *mem = get_End_keepalive(end, j);
+
+      if (mode_M != get_irn_mode(mem))
+        continue;
+
+      mode = follow_mem(irg, mem, mode);
+      if (mode == 0)
+        break;
     }
+  }
+
+  if (mode)
+    set_irg_additional_property(irg, mode);
+  current_ir_graph = rem;
+  return mode;
+}  /* is_pure_function */
+
+/**
+ * Handle calls to const functions.
+ */
+static void handle_const_Calls(env_t *ctx)
+{
+  int i;
+
+  ctx->n_calls_removed_SymConst = 0;
+  ctx->n_calls_removed_Sel      = 0;
+
+  /* all calls of const functions can be transformed */
+  for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
+    ir_graph *irg  = get_irp_irg(i);
+
+    ctx->const_call_list = NULL;
+    ctx->pure_call_list  = NULL;
+    ctx->proj_list = NULL;
+    irg_walk_graph(irg, NULL, collect_calls, ctx);
+
+    if (ctx->const_call_list)
+      fix_const_call_list(irg, ctx->const_call_list, ctx->proj_list);
+  }
+}  /* handle_const_Calls */
+
+/*
+ * optimize function calls by handling const functions
+ */
+void optimize_funccalls(int force_run)
+{
+  int i, n;
+  unsigned num_const = 0;
+  unsigned num_pure  = 0;
+
+  if (! get_opt_function_call())
+    return;
+
+  /* prepare: mark all graphs as not analyzed */
+  n = get_irp_n_irgs();
+  for (i = n - 1; i >= 0; --i)
+    MARK_IRG(get_irp_irg(i));
+
+  /* first step: detect, which functions are const, i.e. do NOT touch any memory */
+  for (i = n - 1; i >= 0; --i) {
+    ir_graph *irg = get_irp_irg(i);
+    unsigned mode = is_pure_function(irg);
+
+    if (mode & mtp_property_const)
+      ++num_const;
+    else if (mode & mtp_property_pure)
+      ++num_pure;
+  }
+
+  if (force_run || num_const > 0) {
+    env_t ctx;
 
+    handle_const_Calls(&ctx);
     if (get_firm_verbosity()) {
-      printf("Detected %d graphs without side effects.\n", num_pure);
-      printf("Optimizes %d(SymConst) + %d(Sel) calls to const functions.\n",
-	     ctx.n_calls_removed_SymConst, ctx.n_calls_removed_Sel);
+      printf("Detected %d graphs without side effects.\n", num_const);
+      printf("Optimizes %d(SymConst) + %d(Sel) calls to const/pure functions.\n",
+	       ctx.n_calls_removed_SymConst, ctx.n_calls_removed_Sel);
     }
   }
   else {