Currently the simplification of SHIFT(a | b, S) is done by
calling simplify_mask_or() with an effective mask corresponding
to the shift instruction.
Prepare the simplification of more complex patterns, involving
a combination of masks, by using a small helper, simplify_mask_shift_or(),
for doing the call to simplify_mask_or() with the appropriate mask.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
simplify.c | 26 ++++++++++++++++++++++----
1 file changed, 22 insertions(+), 4 deletions(-)
diff --git a/simplify.c b/simplify.c
index 7e17f333a..e398d727e 100644
--- a/simplify.c
+++ b/simplify.c
@@ -668,6 +668,24 @@ static int simplify_mask_or(struct instruction *insn, unsigned long long mask, s
return 0;
}
+///
+// try to simplify MASK(SHIFT(OR(a, b), S), M)
+// @sh: the shift instruction
+// @or: the OR instruction
+// @mask: the mask associated to MASK (M):
+// @return: 0 if no changes have been made, one or more REPEAT_* flags otherwise.
+static int simplify_mask_shift_or(struct instruction *sh, struct instruction *or, unsigned long long mask)
+{
+ unsigned long long smask = bits_mask(sh->size);
+ int shift = sh->src2->value;
+
+ if (sh->opcode == OP_LSR)
+ mask <<= shift;
+ else
+ mask >>= shift;
+ return simplify_mask_or(sh, smask & mask, or);
+}
+
static long long check_shift_count(struct instruction *insn, unsigned long long uval)
{
unsigned int size = insn->size;
@@ -775,8 +793,8 @@ static int simplify_shift(struct instruction *insn, pseudo_t pseudo, long long v
case OP_LSR:
goto case_shift_shift;
case OP_OR:
- mask = bits_mask(size - value) << value;
- return simplify_mask_or(insn, mask, def);
+ mask = bits_mask(size);
+ return simplify_mask_shift_or(insn, def, mask);
case OP_SHL:
// replace ((x << S) >> S)
// by (x & (-1 >> S))
@@ -811,8 +829,8 @@ static int simplify_shift(struct instruction *insn, pseudo_t pseudo, long long v
mask = bits_mask(insn->size - value) << value;
goto replace_mask;
case OP_OR:
- mask = bits_mask(size - value);
- return simplify_mask_or(insn, mask, def);
+ mask = bits_mask(size);
+ return simplify_mask_shift_or(insn, def, mask);
case OP_SHL:
case_shift_shift: // also for LSR - LSR
if (def == insn) // cyclic DAG!
--
2.18.0
