[Qemu-devel] [patch] Arm saturating arithmetic bugs.

[Paul Brook]

The patch below fixes a couple of bugs in the arm saturating arithmetic 
instructions. It uses the correct registers, and makes sure the intermediate 
result is saturated properly.

Paul

? target-arm/p
Index: target-arm/op.c
===================================================================
RCS file: /cvsroot/qemu/qemu/target-arm/op.c,v
retrieving revision 1.13
diff -u -p -r1.13 op.c
--- target-arm/op.c     27 Apr 2005 20:25:20 -0000      1.13
+++ target-arm/op.c     13 May 2005 15:53:51 -0000
@@ -805,6 +805,23 @@ void OPPROTO op_subl_T0_T1_saturate(void
   FORCE_RET();
 }
 
+void OPPROTO op_double_T1_saturate(void)
+{
+  int32_t val;
+
+  val = T1;
+  if (val >= 0x40000000) {
+      T1 = 0x7fffffff;
+      env->QF = 1;
+  } else if (val <= (int32_t)0xc0000000) {
+      T1 = 0x80000000;
+      env->QF = 1;
+  } else {
+      T1 = val << 1;
+  }
+  FORCE_RET();
+}
+
 /* thumb shift by immediate */
 void OPPROTO op_shll_T0_im_thumb(void)
 {
Index: target-arm/translate.c
===================================================================
RCS file: /cvsroot/qemu/qemu/target-arm/translate.c,v
retrieving revision 1.24
diff -u -p -r1.24 translate.c
--- target-arm/translate.c      27 Apr 2005 20:25:20 -0000      1.24
+++ target-arm/translate.c      13 May 2005 15:53:51 -0000
@@ -1019,20 +1019,15 @@ static void disas_arm_insn(CPUState * en
         case 0x5: /* saturating add/subtract */
             rd = (insn >> 12) & 0xf;
             rn = (insn >> 16) & 0xf;
-            gen_movl_T0_reg(s, rn);
-            if (op1 & 2) {
-                gen_movl_T1_reg(s, rn);
-                if (op1 & 1) 
-                    gen_op_subl_T0_T1_saturate();
-                else
-                    gen_op_addl_T0_T1_saturate();
-            }
-            gen_movl_T1_reg(s, rm);
+            gen_movl_T0_reg(s, rm);
+            gen_movl_T1_reg(s, rn);
+            if (op1 & 2)
+                gen_op_double_T1_saturate();
             if (op1 & 1)
                 gen_op_subl_T0_T1_saturate();
             else
                 gen_op_addl_T0_T1_saturate();
-            gen_movl_reg_T0(s, rn);
+            gen_movl_reg_T0(s, rd);
             break;
         case 0x8: /* signed multiply */
         case 0xa: