Semantics of x86 uplifting: reduce 'Repeat' ops (#4559)

* Semantics of x86 uplifting: reduce 'Repeat' ops

- Replaced Repeat with bitwise operations for parity calculation.
- Simplified rotate and shift calculations.
- Enhanced static analysis feasibility.

* Update IL outputs of affected tests

librz/arch/isa/x86/common.c

@@ -889,36 +889,21 @@ RZ_IPI RzILOpBool *x86_il_is_sub_underflow(RZ_OWN RZ_NONNULL RzILOpPure *res, RZ
 	return or ;
 }
 
-struct x86_parity_helper_t {
-	RzILOpBool *val; ///< value of parity
-	RzILOpEffect *eff; ///< RzILOpEffect used to find the parity
-};
-
 /**
  * \brief Find the parity of lower 8 bits of \p val
  *
  * \param val
  */
-struct x86_parity_helper_t x86_il_get_parity(RZ_OWN RzILOpPure *val) {
+RzILOpBool *x86_il_get_parity(RZ_OWN RzILOpPure *val) {
 	// assumed that val is an 8-bit wide value
-	RzILOpEffect *setvar = SETL("_popcnt", U8(0));
-	setvar = SEQ2(setvar, SETL("_val", val));
-
-	/* We can stop shifting the "_val" once it is zero,
-	since the value of "_popcnt" wouldn't change any further */
-	RzILOpBool *condition = NON_ZERO(VARL("_val"));
-
-	RzILOpEffect *popcnt = SETL("_popcnt", ADD(VARL("_popcnt"), BOOL_TO_BV(LSB(VARL("_val")), 8)));
-	popcnt = SEQ2(popcnt, SETL("_val", SHIFTR0(VARL("_val"), U8(1))));
 
-	RzILOpEffect *repeat_eff = REPEAT(condition, popcnt);
-
-	struct x86_parity_helper_t ret = {
-		.val = IS_ZERO(MOD(VARL("_popcnt"), U8(2))),
-		.eff = SEQ2(setvar, repeat_eff)
-	};
-
-	return ret;
+	// A parity calculation can be reduced to nested shift-right and xor operations.
+	// see https://github.com/BinaryAnalysisPlatform/bap/blob/master/plugins/x86/x86_lifter.ml#L215
+	RzILOpPure *accumulate = LET("_val", val,
+		LET("_c4", LOGXOR(VARLP("_val"), SHIFTR0(VARLP("_val"), U8(4))),
+			LET("_c2", LOGXOR(VARLP("_c4"), SHIFTR0(VARLP("_c4"), U8(2))),
+				LOGXOR(VARLP("_c2"), SHIFTR0(VARLP("_c2"), U8(1))))));
+	return INV(LSB(accumulate));
 }
 
 /**
@@ -928,12 +913,12 @@ RZ_IPI RzILOpEffect *x86_il_set_result_flags_bits(RZ_OWN RZ_NONNULL RzILOpPure *
 	rz_return_val_if_fail(result, NULL);
 
 	RzILOpEffect *set = SETL("_result", result);
-	struct x86_parity_helper_t pf = x86_il_get_parity(UNSIGNED(8, VARL("_result")));
+	RzILOpBool *pf = x86_il_get_parity(UNSIGNED(8, VARL("_result")));
 	RzILOpBool *zf = IS_ZERO(VARL("_result"));
 	RzILOpBool *sf = MSB(VARL("_result"));
 
-	return SEQ5(set, pf.eff,
-		SETG(EFLAGS(PF), pf.val),
+	return SEQ4(set,
+		SETG(EFLAGS(PF), pf),
 		SETG(EFLAGS(ZF), zf),
 		SETG(EFLAGS(SF), sf));
 }