Assignments to pc => goto

Author: uxmal

src/Arch/Arm/ThumbRewriter.Alu.cs

@@ -18,6 +18,7 @@
  */
 #endregion
 
+using Gee.External.Capstone.Arm;
 using Reko.Core;
 using Reko.Core.Expressions;
 using Reko.Core.Rtl;
@@ -120,12 +121,9 @@ private void RewriteLdr(DataType dtDst, DataType dtSrc)
                 var baseReg = GetReg(ops[1].MemoryValue.BaseRegister);
                 Predicate(itStateCondition, tmp, src);
                 Predicate(itStateCondition, baseReg, emitter.IAdd(baseReg, RewriteOp(ops[2])));
-                Predicate(itStateCondition, dst, tmp);
-            }
-            else 
-            {
-                Predicate(itStateCondition, dst, src);
+                src = tmp;
             }
+            Predicate(itStateCondition, dst, src);
         }
 
         private void RewriteLdrex()
@@ -190,25 +188,27 @@ private void RewriteMvn()
         private void RewritePop()
         {
             var sp = frame.EnsureRegister(A32Registers.sp);
+            emitter.Assign(sp, emitter.IAdd(sp, Constant.Int32(ops.Length * 4)));
             int offset = ops.Length * 4;
             foreach (var op in ops.OrderByDescending(o => o.RegisterValue.Value))
             {
-                offset -= 4;
-                emitter.Assign(
+                Predicate(
+                    ArmCodeCondition.AL,
                     GetReg(op.RegisterValue.Value),
-                    emitter.LoadDw(emitter.IAdd(sp, Constant.Int32(offset))));
+                    emitter.LoadDw(emitter.ISub(sp, Constant.Int32(offset))));
+                offset -= 4;
             }
-            emitter.Assign(sp, emitter.IAdd(sp, Constant.Int32( ops.Length * 4)));
         }
 
         private void RewritePush()
         {
             var sp = frame.EnsureRegister(A32Registers.sp);
             emitter.Assign(sp, emitter.ISub(sp, Constant.Int32( ops.Length * 4)));
             int offset = 0;
-            foreach (var op in ops.OrderBy(o => o.RegisterValue.Value))
+            foreach (var op in ops.OrderByDescending(o => o.RegisterValue.Value))
             {
-                emitter.Assign(
+                Predicate(
+                    ArmCodeCondition.AL,
                     emitter.LoadDw(emitter.IAdd(sp, Constant.Int32(offset))),
                     GetReg(op.RegisterValue.Value));
                 offset += 4;

src/Arch/Arm/ThumbRewriter.cs

@@ -256,11 +256,20 @@ private void Predicate(ArmCodeCondition cond, RtlInstruction instr)
 
         private void Predicate(ArmCodeCondition cond, Expression dst, Expression src)
         {
-            var ass = new RtlAssignment(dst, src);
+            RtlInstruction instr;
+            Identifier id;
+            if (dst.As<Identifier>(out id) && id.Storage == A32Registers.pc)
+            {
+                instr = new RtlGoto(src, RtlClass.Transfer);
+            }
+            else
+            {
+                instr = new RtlAssignment(dst, src);
+            }
             if (cond == ArmCodeCondition.AL)
-                emitter.Emit(ass);
+                emitter.Emit(instr);
             else
-                emitter.If(TestCond(cond), ass);
+                emitter.If(TestCond(cond), instr);
         }
     }
 }

src/UnitTests/Arch/Arm/ThumbRewriterTests.cs

@@ -5773,8 +5773,8 @@ public void ThumbRw_push()
             AssertCode(
                 "0|00100000(4): 3 instructions",
                 "1|L--|sp = sp - 8",
-                "2|L--|Mem0[sp + 0:word32] = lr",
-                "3|L--|Mem0[sp + 4:word32] = fp");
+                "2|L--|Mem0[sp + 0:word32] = fp",
+                "3|L--|Mem0[sp + 4:word32] = lr");
         }
 
         [Test]
@@ -5783,9 +5783,9 @@ public void ThumbRw_pop()
             BuildTest(0xE8BD, 0x8800); // pop.w\t{fp,pc}
             AssertCode(
                 "0|00100000(4): 3 instructions",
-                "1|L--|fp = Mem0[sp + 4:word32]",
-                "2|L--|pc = Mem0[sp + 0:word32]",
-                "3|L--|sp = sp + 8");
+                "1|L--|sp = sp + 8",
+                "2|L--|fp = Mem0[sp - 8:word32]",
+                "3|T--|goto Mem0[sp - 4:word32]");
         }
 
         [Test]
@@ -6150,7 +6150,7 @@ public void ThumbRw_ldr_postIndex()
                 "0|00100000(4): 3 instructions",
                 "1|L--|v4 = Mem0[sp:word32]",
                 "2|L--|sp = sp + 12",
-                "3|L--|pc = v4");
+                "3|T--|goto v4");
         }
           [Test]
         public void ThumbRw_strb_preIndex()
@@ -6172,6 +6172,13 @@ public void ThumbRw_strb_postIndex()
                 "2|L--|r2 = r2 + 1");
         }
 
-   
+        [Test]
+        public void ThumbRw_ldr_pc()
+        {
+            BuildTest(0xF8DC, 0xF000);  // ldr         pc,[r12]
+            AssertCode(
+                "0|00100000(4): 1 instructions",
+                "1|T--|goto Mem0[ip:word32]");
+        }
     }
 }