This is especially usefull when simplifying code
accessing bitfields.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
simplify.c | 29 ++++++++++++++++++++++++++++-
validation/bitfield-size.c | 4 +---
2 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/simplify.c b/simplify.c
index 9893613da..f1a898700 100644
--- a/simplify.c
+++ b/simplify.c
@@ -412,6 +412,32 @@ static int simplify_asr(struct instruction *insn, pseudo_t pseudo, long long val
return 0;
}
+static int simplify_lsr(struct instruction *insn, pseudo_t pseudo, long long value)
+{
+ struct instruction *def;
+ unsigned long long mask;
+
+ if (!value)
+ return replace_with_pseudo(insn, pseudo);
+ switch (def_opcode(insn->src1)) {
+ case OP_AND:
+ // replace (A & M) >> S
+ // by (A >> S) & (M >> S)
+ def = insn->src1->def;
+ if (!constant(def->src2))
+ break;
+ if (nbr_pseudo_users(insn->src1) > 1)
+ break;
+ mask = def->src2->value;
+ def->opcode = OP_LSR;
+ def->src2 = value_pseudo(value);
+ insn->opcode = OP_AND;
+ insn->src2 = value_pseudo(mask >> value);
+ return REPEAT_CSE;
+ }
+ return 0;
+}
+
static int simplify_mul_div(struct instruction *insn, long long value)
{
unsigned long long sbit = 1ULL << (insn->size - 1);
@@ -562,13 +588,14 @@ static int simplify_constant_rightside(struct instruction *insn)
case OP_ADD:
case OP_OR: case OP_XOR:
case OP_SHL:
- case OP_LSR:
case_neutral_zero:
if (!value)
return replace_with_pseudo(insn, insn->src1);
return 0;
case OP_ASR:
return simplify_asr(insn, insn->src1, value);
+ case OP_LSR:
+ return simplify_lsr(insn, insn->src1, value);
case OP_MODU: case OP_MODS:
if (value == 1)
diff --git a/validation/bitfield-size.c b/validation/bitfield-size.c
index c8c94bb15..34400479a 100644
--- a/validation/bitfield-size.c
+++ b/validation/bitfield-size.c
@@ -36,8 +36,6 @@ unsigned int get_pbfi_b(struct bfi *bf) { return bf->b; }
* check-output-ignore
*
* check-output-excludes: cast\\.4
- * check-output-pattern-6-times: cast\\.
* check-output-pattern-6-times: lsr\\..*\\$6
- * check-output-pattern-6-times: and\\..*\\$15
- * check-output-pattern-6-times: and\\..*\\$960
+ * check-output-pattern-12-times: and\\..*\\$15
*/
--
2.13.2
--
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