ir: dead-code-removal, move constants -> ast_utils/

* removes all unused instructions
* since functions are not yet marked with no-side-effects, all calls
    are assumed to have side-effects
* moved constants.c2 to ast_utils/ since AST depends on it

Author: bvdberg

common/constants.c2 renamed to ast_utils/constants.c2

@@ -32,7 +32,7 @@ const char* col_Attr = color.Bmagenta;
 const char* col_Unknown = color.Yellow;
 const char* col_Value = color.Magenta;
 const char* col_Register = color.Cyan;
-const char* col_Data = color.Bgreen;
+const char* col_Data = color.Bcyan;
 const char* col_Slot = color.Bcyan;
 const char* col_Temp = color.Bgreen;
 const char* col_Param = color.Cyan;

ir/print.c2

@@ -374,30 +374,69 @@ fn void Tools.eliminateCopies(Tools* t, FunctionInfo* fi) {
     }
 }
 
+
+fn void Tools.checkRef(Tools* t, Ref r) {
+    if (r.isTemp()) t.usage.incr(r.value);
+}
+
 fn void Tools.fillUsage(Tools* t, FunctionInfo* fi) {
     t.usage.clear(fi.instructions.getCount());
 
     // Usage: counter both usage and if it has a result.
     // count 0 means: has no result, (of course) not used
     // count 1 means: has result, not used (could still have side effects)
     // count 2+ means: used
+
     Instr* all = fi.instructions.get(0);
     for (u32 i=0; i<fi.instructions.getCount(); i++) {
         Instr* is = &all[i];
         if (is.hasResult()) t.usage.incr(i);
-        if (is.isPhi()) {
+
+        switch (is.getKind()) {
+        case Call:
+            // TODO check if call with side effects.
+            // TEMP do extra incr then so it will not be pruned (could be void, so incr twice)
+            t.usage.incr(i);
+            t.usage.incr(i);
+            t.checkRef(is.args[0]);
+            t.checkRef(is.args[1]);
+            if (is.args[1].isRefList()) {
+                const Ref* refs = fi.refs.get(is.args[1].value);
+                u32 j = 0;
+                while (refs[j].kind != RefKind.None) {
+                    t.checkRef(refs[j]);
+                    j++;
+                }
+            }
+            break;
+        case Switch:
+            t.checkRef(is.args[0]);
+            break;
+        case Phi:
             PhiClause* clauses = fi.phis.get(is.phi_clauses.start);
             for (u32 p=0; p<is.phi_clauses.count; p++) {
-                Ref* r = &clauses[p].ref;
-                if (r.isTemp()) t.usage.incr(r.value);
+                t.checkRef(clauses[p].ref);
             }
-        } else {
-            Ref* r = &is.args[0];
-            if (r.isTemp()) t.usage.incr(r.value);
-            r = &is.args[1];
-            if (r.isTemp()) t.usage.incr(r.value);
+            break;
+        default:
+            t.checkRef(is.args[0]);
+            t.checkRef(is.args[1]);
+            break;
         }
     }
+
+    //t.usage.dump();
+    t.usage.fillQueue();
+
+    while (t.usage.hasWork()) {
+        u32 i = t.usage.popHead();
+        Instr* is = &all[i];
+        Ref* r = &is.args[0];
+        if (r.isTemp()) t.usage.decr(r.value);
+        r = &is.args[1];
+        if (r.isTemp()) t.usage.decr(r.value);
+        is.clear();
+    }
 }
 
 #if 0

ir/ssa.c2

@@ -10,13 +10,21 @@ public type Counter struct {
     u32 count;
     u32 capacity;
     u8* counts;
+    u32 max_idx;
+
+    u32[64] work_queue; // TODO make re-sizeable
+    u32 queue_head;
+    u32 queue_count;
 }
 
 public fn void Counter.init(Counter* c, u32 cap) {
     c.count = 0;
     c.capacity = 0;
     c.counts = nil;
     c.resize(cap);
+    c.max_idx = 0;
+    c.queue_head = 0;
+    c.queue_count = 0;
 }
 
 public fn void Counter.free(Counter* c) {
@@ -32,26 +40,61 @@ fn void Counter.resize(Counter* c, u32 cap) {
 public fn void Counter.clear(Counter* c, u32 cap) {
     if (cap > c.capacity) c.resize(cap);
     c.count = cap;
+    // TODO could be costly
     memset(c.counts, 0, cap);
+    c.max_idx = 0;
+    c.queue_head = 0;
+    c.queue_count = 0;
 }
 
 public fn void Counter.incr(Counter* c, u32 idx) {
     //assert(c.counts[idx] != u8.max);  // u8
     assert(c.counts[idx] != c2.max_u8);
     c.counts[idx]++;
+    if (idx > c.max_idx) c.max_idx = idx;
 }
 
-/*
-public fn bool Counter.decr(Counter* c, u32 idx) {
+public fn void Counter.decr(Counter* c, u32 idx) {
     c.counts[idx]--;
-    return c.counts[idx] != 0;
+    if (c.counts[idx] == 1) {
+        // add to work_queue if not already in
+        u32 pos = c.queue_head;
+        for (u32 i=0; i<c.queue_count; i++) {
+            if (c.work_queue[pos] == idx) return; // already in
+            pos = (pos + 1) % elemsof(c.work_queue);
+        }
+        assert(c.queue_count != elemsof(c.work_queue));
+        c.work_queue[pos] = idx;
+        c.queue_count++;
+    }
+}
+
+public fn bool Counter.hasWork(const Counter* c) {
+    return c.queue_count != 0;
+}
+
+public fn void Counter.fillQueue(Counter* c) {
+    u32 i = c.max_idx;
+    while (i != c2.max_u32) {
+        if (c.counts[i] == 1) {
+            assert(c.queue_count != elemsof(c.work_queue));
+            // fill linearly since it starts empty
+            c.work_queue[c.queue_count++] = i;
+        }
+        i--;
+    }
+}
+
+public fn u32 Counter.popHead(Counter* c) {
+    u32 idx = c.work_queue[c.queue_head];
+    c.queue_head = (c.queue_head + 1) % elemsof(c.work_queue);
+    c.queue_count--;
+    return idx;
 }
-*/
 
 public fn void Counter.dump(const Counter* c) @(unused) {
-    stdio.printf("Usage counter (%d)\n", c.count);
-    for (u32 i=0; i<c.count; i++) {
-        stdio.printf("  [%3d] %d\n", i, c.counts[i]);
+    for (u32 i=0; i<=c.max_idx; i++) {
+        if (c.counts[i] != 0) stdio.printf("  [%3d] %d\n", i, c.counts[i]);
     }
 }
 

ir/usage_counter.c2

@@ -9,7 +9,6 @@ set common
     common/build_target.c2
     common/component.c2
     common/console.c2
-    common/constants.c2
     common/diagnostics.c2
     common/file/reader.c2
     common/file/writer.c2
@@ -30,6 +29,7 @@ set ast
     ast_utils/attr.c2
     ast_utils/attr_table.c2
     ast_utils/color.c2
+    ast_utils/constants.c2
     ast_utils/context.c2
     ast_utils/number_radix.c2
     ast_utils/src_loc.c2
@@ -135,7 +135,6 @@ set yaml
 end
 
 set refs
-    common/constants.c2
     common/linked_list.c2
     common/quicksort.c2
     common/utils.c2
@@ -313,6 +312,8 @@ executable c2tags
 
     (refs)
 
+    ast_utils/constants.c2
+
     tools/c2tags.c2
 end
 
@@ -321,6 +322,8 @@ executable c2rename
     $backend c
     $config RadixTreeValue
 
+    ast_utils/constants.c2
+
     common/file/reader.c2
     common/file/writer.c2
 
@@ -343,9 +346,9 @@ executable tester
 #    $config TesterDebug
 
     ast_utils/color.c2
+    ast_utils/constants.c2
     ast_utils/string_buffer.c2
 
-    common/constants.c2
     common/file/reader.c2
     common/file/writer.c2
     common/string_utils.c2
@@ -363,12 +366,12 @@ executable c2cat
 	$backend c
 
     ast_utils/color.c2
+    ast_utils/constants.c2
     ast_utils/number_radix.c2
     ast_utils/src_loc.c2
     ast_utils/string_buffer.c2
     ast_utils/string_pool.c2
 
-    common/constants.c2
     common/file/reader.c2
     common/string_list.c2
     common/utf8.c2
@@ -392,12 +395,12 @@ executable c2loc
 	$backend c
 
     ast_utils/color.c2
+    ast_utils/constants.c2
     ast_utils/src_loc.c2
     ast_utils/string_buffer.c2
     ast_utils/string_pool.c2
 
     common/build_target.c2
-    common/constants.c2
     common/file/reader.c2
     common/library_list.c2
     common/source_mgr.c2