[PATCH 5/6] simplify ((x & M) << S) when (M << S) == 0

[Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>]

The instructions SHL(AND(x, M), S) can be simplified to 0
if (M << S) == 0.

For example code like:
	unsigned foo(unsigned x)
	{
		return (x & 0xfff00000) << 12;
	}

is now simplified into:
	foo:
		ret.32      $0

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
 simplify.c                  | 11 +++++++++++
 validation/optim/shl-and0.c |  1 -
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/simplify.c b/simplify.c
index 8ace8a5da..5c1c98088 100644
--- a/simplify.c
+++ b/simplify.c
@@ -689,6 +689,17 @@ static int simplify_shift(struct instruction *insn, pseudo_t pseudo, long long v
 		if (value >= size)
 			goto zero;
 		switch(DEF_OPCODE(def, pseudo)) {
+		case OP_AND:
+			// simplify (A & M) << S
+			if (!constant(def->src2))
+				break;
+			mask = bits_mask(insn->size) >> value;
+			omask = def->src2->value;
+			nmask = omask & mask;
+			if (nmask == 0)
+				return replace_with_pseudo(insn, value_pseudo(0));
+			// do not simplify into ((A << S) & (M << S))
+			break;
 		case OP_LSR:
 			// replace ((x >> S) << S)
 			// by      (x & (-1 << S))
diff --git a/validation/optim/shl-and0.c b/validation/optim/shl-and0.c
index 63b20501c..6cbe8e58f 100644
--- a/validation/optim/shl-and0.c
+++ b/validation/optim/shl-and0.c
@@ -7,7 +7,6 @@ unsigned foo(unsigned x)
 /*
  * check-name: shl-and0
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-contains: ret\\..*\\$0$
-- 
2.18.0