Merge pull request #8052 from WalterBright/fix18534

fix Issue 18534 - Wrong code for ?: operator when compiling with -O

src/dmd/backend/cod2.c

@@ -1998,9 +1998,19 @@ void cdcond(CodeBuilder& cdb,elem *e,regm_t *pretregs)
         targ_size_t v1,v2;
         int opcode;
 
-        retregs = *pretregs & (ALLREGS | mBP);
-        if (!retregs)
-            retregs = ALLREGS;
+        if (sz2 != 1 || I64)
+        {
+            retregs = *pretregs & (ALLREGS | mBP);
+            if (!retregs)
+                retregs = ALLREGS;
+        }
+        else
+        {
+            retregs = *pretregs & BYTEREGS;
+            if (!retregs)
+                retregs = BYTEREGS;
+        }
+
         cdcmp_flag = 1;
         v1 = e21->EV.Vllong;
         v2 = e22->EV.Vllong;
@@ -2046,15 +2056,15 @@ void cdcond(CodeBuilder& cdb,elem *e,regm_t *pretregs)
             {
                 v1 -= v2;
                 cdb.genc2(opcode,grex | modregrmx(3,4,reg),v1);   // AND reg,v1-v2
-                if (I64 && sz1 == 1 && reg >= 4)
+                if (I64 && sz2 == 1 && reg >= 4)
                     code_orrex(cdb.last(), REX);
                 if (v2 == 1 && !I64)
                     cdb.gen1(0x40 + reg);                     // INC reg
                 else if (v2 == -1L && !I64)
                     cdb.gen1(0x48 + reg);                     // DEC reg
                 else
                 {   cdb.genc2(opcode,grex | modregrmx(3,0,reg),v2);   // ADD reg,v2
-                    if (I64 && sz1 == 1 && reg >= 4)
+                    if (I64 && sz2 == 1 && reg >= 4)
                         code_orrex(cdb.last(), REX);
                 }
             }

test/runnable/test18534.d

@@ -0,0 +1,18 @@
+/* REQUIRED_ARGS: -O
+ * PERMUTE_ARGS:
+ */
+
+// https://issues.dlang.org/show_bug.cgi?id=18534
+
+auto blah(char ch) { return ch; }
+
+auto foo(int i)
+{
+    return blah(i ? 'A' : 'A');
+}
+
+void main()
+{
+    auto c = foo(0);
+    assert(c == 'A');
+}