Add algebraic simplification as follows:

  Add64(0,x) ==> x
  Add32(0,x) ==> x
  Sub64(x,0) ==> x

Add helper functions: isZeroU32 and isZeroU64.

git-svn-id: svn://svn.valgrind.org/vex/trunk@2180

diff --git a/VEX/priv/ir_opt.c b/VEX/priv/ir_opt.c
index b7746458a34272c37737690f7ab734db81ec4655..8da10ff7786b7e07786cfe07737a430886511ec8 100644 (file)
--- a/VEX/priv/ir_opt.c
+++ b/VEX/priv/ir_opt.c
@@ -917,6 +917,22 @@ static Bool sameIRTempsOrIcoU32s ( IRExpr* e1, IRExpr* e2 )
    }
 }
 
+/* Is this literally IRExpr_Const(IRConst_U32(0)) ? */
+static Bool isZeroU32 ( IRExpr* e )
+{
+   return toBool( e->tag == Iex_Const 
+                  && e->Iex.Const.con->tag == Ico_U32
+                  && e->Iex.Const.con->Ico.U32 == 0);
+}
+
+/* Is this literally IRExpr_Const(IRConst_U64(0)) ? */
+static Bool isZeroU64 ( IRExpr* e )
+{
+   return toBool( e->tag == Iex_Const 
+                  && e->Iex.Const.con->tag == Ico_U64
+                  && e->Iex.Const.con->Ico.U64 == 0);
+}
+
 static Bool notBool ( Bool b )
 {
    if (b == True) return False;
@@ -1594,11 +1610,18 @@ static IRExpr* fold_Expr ( IRExpr* e )
             e2 = e->Iex.Binop.arg1;
          } else
 
-         /* Or32/Add32/Max32U(x,0) ==> x */
-         if ((e->Iex.Binop.op == Iop_Add32 
-              || e->Iex.Binop.op == Iop_Or32 || e->Iex.Binop.op == Iop_Max32U)
-             && e->Iex.Binop.arg2->tag == Iex_Const
-             && e->Iex.Binop.arg2->Iex.Const.con->Ico.U32 == 0) {
+         /* Or32/Add32/Max32U(x,0) ==> x
+            Or32/Add32/Max32U(0,x) ==> x */
+         if (e->Iex.Binop.op == Iop_Add32
+             || e->Iex.Binop.op == Iop_Or32 || e->Iex.Binop.op == Iop_Max32U) {
+            if (isZeroU32(e->Iex.Binop.arg2))
+               e2 = e->Iex.Binop.arg1;
+            else if (isZeroU32(e->Iex.Binop.arg1))
+               e2 = e->Iex.Binop.arg2;
+         } else
+
+         /* Sub64(x,0) ==> x */
+         if (e->Iex.Binop.op == Iop_Sub64 && isZeroU64(e->Iex.Binop.arg2)) {
             e2 = e->Iex.Binop.arg1;
          } else
 
@@ -1639,11 +1662,13 @@ static IRExpr* fold_Expr ( IRExpr* e )
          } else
          /* NB no Add16(t,t) case yet as no known test case exists */
 
-         /* Or64/Add64(x,0) ==> x */
-         if ((e->Iex.Binop.op == Iop_Add64 || e->Iex.Binop.op == Iop_Or64)
-             && e->Iex.Binop.arg2->tag == Iex_Const
-             && e->Iex.Binop.arg2->Iex.Const.con->Ico.U64 == 0) {
-            e2 = e->Iex.Binop.arg1;
+         /* Or64/Add64(x,0) ==> x
+            Or64/Add64(0,x) ==> x */
+         if (e->Iex.Binop.op == Iop_Add64 || e->Iex.Binop.op == Iop_Or64) {
+            if (isZeroU64(e->Iex.Binop.arg2))
+               e2 = e->Iex.Binop.arg1;
+            else if (isZeroU64(e->Iex.Binop.arg1))
+               e2 = e->Iex.Binop.arg2;
          } else
 
          /* And32(x,0xFFFFFFFF) ==> x */
@@ -1674,20 +1699,6 @@ static IRExpr* fold_Expr ( IRExpr* e )
             e2 = e->Iex.Binop.arg2;
          } else
 
-         /* Or32/Max32U(0,x) ==> x */
-         if ((e->Iex.Binop.op == Iop_Or32 || e->Iex.Binop.op == Iop_Max32U)
-             && e->Iex.Binop.arg1->tag == Iex_Const
-             && e->Iex.Binop.arg1->Iex.Const.con->Ico.U32 == 0) {
-            e2 = e->Iex.Binop.arg2;
-         } else
-
-         /* Or64(0,x) ==> x */
-         if (e->Iex.Binop.op == Iop_Or64
-             && e->Iex.Binop.arg1->tag == Iex_Const
-             && e->Iex.Binop.arg1->Iex.Const.con->Ico.U64 == 0) {
-            e2 = e->Iex.Binop.arg2;
-         } else
-
          /* Or8/16/32/64/V128(t,t) ==> t, for some IRTemp t */
          /* And8/16/32/64(t,t) ==> t, for some IRTemp t */
          /* Max32U(t,t) ==> t, for some IRTemp t */