The instructions SHL(AND(x, M), S) can be simplified into SHL(x, S)
if (M << S) == (-1 << S).
For example, code like:
unsigned foo(unsigned x)
{
return (x & 0x000fffff) << 12;
}
is now optimized into:
foo:
shl.32 %r3 <- %arg1, $12
ret.32 %r3
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
simplify.c | 2 ++
validation/optim/shl-and1.c | 1 -
2 files changed, 2 insertions(+), 1 deletion(-)
diff --git a/simplify.c b/simplify.c
index 5c1c98088..1f2ff6e67 100644
--- a/simplify.c
+++ b/simplify.c
@@ -698,6 +698,8 @@ static int simplify_shift(struct instruction *insn, pseudo_t pseudo, long long v
nmask = omask & mask;
if (nmask == 0)
return replace_with_pseudo(insn, value_pseudo(0));
+ if (nmask == mask)
+ return replace_pseudo(insn, &insn->src1, def->src1);
// do not simplify into ((A << S) & (M << S))
break;
case OP_LSR:
diff --git a/validation/optim/shl-and1.c b/validation/optim/shl-and1.c
index b7876e4e0..f6489cf00 100644
--- a/validation/optim/shl-and1.c
+++ b/validation/optim/shl-and1.c
@@ -11,7 +11,6 @@ unsigned foo(unsigned x)
/*
* check-name: shl-and1
* check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
*
* check-output-ignore
* check-output-contains: ret\\..*\\$0$
--
2.18.0
