Merge pull request #268 from sysprog21/improve-ssa

Improve SSA optimizations

Author: jserv

src/arm.c

@@ -329,6 +329,12 @@ int __blx(arm_cond_t cond, arm_reg rd)
     return arm_encode(cond, 18, 15, 15, rd + 3888);
 }
 
+int __bx(arm_cond_t cond, arm_reg rm)
+{
+    /* BX: Branch and Exchange */
+    return (cond << 28) | 0x012FFF10 | rm;
+}
+
 int __mul(arm_cond_t cond, arm_reg rd, arm_reg r1, arm_reg r2)
 {
     return arm_encode(cond, 0, rd, 0, (r1 << 8) + 144 + r2);

src/parser.c

@@ -1750,18 +1750,40 @@ void read_expr_operand(block_t *parent, basic_block_t **bb)
         read_expr_operand(parent, bb);
 
         rs1 = opstack_pop();
-        vd = require_var(parent);
-        gen_name_to(vd->var_name);
-        opstack_push(vd);
-        add_insn(parent, *bb, OP_log_not, vd, rs1, NULL, 0, NULL);
+
+        /* Constant folding for logical NOT */
+        if (rs1 && rs1->is_const && !rs1->ptr_level && !rs1->is_global) {
+            vd = require_var(parent);
+            gen_name_to(vd->var_name);
+            vd->is_const = true;
+            vd->init_val = !rs1->init_val;
+            opstack_push(vd);
+            add_insn(parent, *bb, OP_load_constant, vd, NULL, NULL, 0, NULL);
+        } else {
+            vd = require_var(parent);
+            gen_name_to(vd->var_name);
+            opstack_push(vd);
+            add_insn(parent, *bb, OP_log_not, vd, rs1, NULL, 0, NULL);
+        }
     } else if (lex_accept(T_bit_not)) {
         read_expr_operand(parent, bb);
 
         rs1 = opstack_pop();
-        vd = require_var(parent);
-        gen_name_to(vd->var_name);
-        opstack_push(vd);
-        add_insn(parent, *bb, OP_bit_not, vd, rs1, NULL, 0, NULL);
+
+        /* Constant folding for bitwise NOT */
+        if (rs1 && rs1->is_const && !rs1->ptr_level && !rs1->is_global) {
+            vd = require_var(parent);
+            gen_name_to(vd->var_name);
+            vd->is_const = true;
+            vd->init_val = ~rs1->init_val;
+            opstack_push(vd);
+            add_insn(parent, *bb, OP_load_constant, vd, NULL, NULL, 0, NULL);
+        } else {
+            vd = require_var(parent);
+            gen_name_to(vd->var_name);
+            opstack_push(vd);
+            add_insn(parent, *bb, OP_bit_not, vd, rs1, NULL, 0, NULL);
+        }
     } else if (lex_accept(T_ampersand)) {
         handle_address_of_operator(parent, bb);
     } else if (lex_accept(T_asterisk)) {
@@ -2179,10 +2201,22 @@ void read_expr_operand(block_t *parent, basic_block_t **bb)
 
         if (is_neg) {
             rs1 = opstack_pop();
-            vd = require_var(parent);
-            gen_name_to(vd->var_name);
-            opstack_push(vd);
-            add_insn(parent, *bb, OP_negate, vd, rs1, NULL, 0, NULL);
+
+            /* Constant folding for negation */
+            if (rs1 && rs1->is_const && !rs1->ptr_level && !rs1->is_global) {
+                vd = require_var(parent);
+                gen_name_to(vd->var_name);
+                vd->is_const = true;
+                vd->init_val = -rs1->init_val;
+                opstack_push(vd);
+                add_insn(parent, *bb, OP_load_constant, vd, NULL, NULL, 0,
+                         NULL);
+            } else {
+                vd = require_var(parent);
+                gen_name_to(vd->var_name);
+                opstack_push(vd);
+                add_insn(parent, *bb, OP_negate, vd, rs1, NULL, 0, NULL);
+            }
         }
     }
 }