From 3ff77a1d6fbcf08fc6964e8149d188c791cb7f16 Mon Sep 17 00:00:00 2001
From: Edmund Grimley Evans <Edmund.Grimley.Evans@gmail.com>
Date: Fri, 20 Nov 2015 23:33:49 +0000
Subject: [PATCH] Improve constant propagation with "&&" and "||".

---
 TODO                        |   1 -
 tccgen.c                    | 103 +++++++++++++++++++-----------------
 tests/tests2/78_vla_label.c |   6 ++-
 3 files changed, 58 insertions(+), 52 deletions(-)

diff --git a/TODO b/TODO
index ea57823..ffe4ad1 100644
--- a/TODO
+++ b/TODO
@@ -68,7 +68,6 @@ Not critical:
   to suppress VT_LOCAL and use a base register instead).
 - interactive mode / integrated debugger
 - fix preprocessor symbol redefinition
-- better constant opt (&&, ||, ?:)
 - add portable byte code generator and interpreter for other
   unsupported architectures.
 - C++: variable declaration in for, minimal 'class' support.
diff --git a/tccgen.c b/tccgen.c
index e2d9e21..3b5ad75 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -4453,80 +4453,83 @@ static void expr_or(void)
     }
 }
 
-/* XXX: fix this mess */
-static void expr_land_const(void)
-{
-    expr_or();
-    while (tok == TOK_LAND) {
-        next();
-        expr_or();
-        gen_op(TOK_LAND);
-    }
-}
-
-/* XXX: fix this mess */
-static void expr_lor_const(void)
-{
-    expr_land_const();
-    while (tok == TOK_LOR) {
-        next();
-        expr_land_const();
-        gen_op(TOK_LOR);
-    }
-}
-
-/* only used if non constant */
 static void expr_land(void)
 {
-    int t;
-
     expr_or();
     if (tok == TOK_LAND) {
-        t = 0;
-        save_regs(1);
-        for(;;) {
-            t = gvtst(1, t);
-            if (tok != TOK_LAND) {
-                vseti(VT_JMPI, t);
-                break;
-            }
+        if ((vtop->r & (VT_VALMASK | VT_LVAL | VT_SYM)) == VT_CONST) {
+            CType ctb, cti;
+            ctb.t = VT_BOOL;
+            cti.t = VT_INT;
             next();
-            expr_or();
+            gen_cast(&ctb);
+            if (vtop->c.i) {
+                vpop();
+                expr_land();
+                gen_cast(&ctb);
+            } else {
+                expr_land();
+                vpop();
+            }
+            gen_cast(&cti);
+        } else {
+            int t = 0;
+            save_regs(1);
+            for(;;) {
+                t = gvtst(1, t);
+                if (tok != TOK_LAND) {
+                    vseti(VT_JMPI, t);
+                    break;
+                }
+                next();
+                expr_or();
+            }
         }
     }
 }
 
 static void expr_lor(void)
 {
-    int t;
-
     expr_land();
     if (tok == TOK_LOR) {
-        t = 0;
-        save_regs(1);
-        for(;;) {
-            t = gvtst(0, t);
-            if (tok != TOK_LOR) {
-                vseti(VT_JMP, t);
-                break;
-            }
+        if ((vtop->r & (VT_VALMASK | VT_LVAL | VT_SYM)) == VT_CONST) {
+            CType ctb, cti;
+            ctb.t = VT_BOOL;
+            cti.t = VT_INT;
             next();
-            expr_land();
+            gen_cast(&ctb);
+            if (vtop->c.i) {
+                expr_lor();
+                vpop();
+            } else {
+                vpop();
+                expr_lor();
+                gen_cast(&ctb);
+            }
+            gen_cast(&cti);
+        } else {
+            int t = 0;
+            save_regs(1);
+            for(;;) {
+                t = gvtst(0, t);
+                if (tok != TOK_LOR) {
+                    vseti(VT_JMP, t);
+                    break;
+                }
+                next();
+                expr_land();
+            }
         }
     }
 }
 
-/* XXX: better constant handling */
 static void expr_cond(void)
 {
     int tt, u, r1, r2, rc, t1, t2, bt1, bt2;
     SValue sv;
     CType type, type1, type2;
 
-    if (const_wanted)
-        expr_lor_const();
-    else
-        expr_lor();
+    expr_lor();
     if (tok == '?') {
         next();
         if ((vtop->r & (VT_VALMASK | VT_LVAL | VT_SYM)) == VT_CONST) {
diff --git a/tests/tests2/78_vla_label.c b/tests/tests2/78_vla_label.c
index 93a8b08..39654c6 100644
--- a/tests/tests2/78_vla_label.c
+++ b/tests/tests2/78_vla_label.c
@@ -17,9 +17,13 @@ void f2(void)
 {
     goto start;
     {
-        int a[1 ? 1 : 1]; /* not a variable-length array */
+        int a[1 && 1]; /* not a variable-length array */
+        int b[1 || 1]; /* not a variable-length array */
+        int c[1 ? 1 : 1]; /* not a variable-length array */
     start:
         a[0] = 0;
+        b[0] = 0;
+        c[0] = 0;
     }
 }