... if it is an IOR with a constant with all bits set in the mode
that is truncated to, for example. Handle that case.
With this patch the problematic situation for the PR81423 testcase
isn't even reached; but the next patch fixes that anyway.
Bootstrapped and tested on powerpc64-linux {-m32,-m64} and on
x86_64-linux. Is this okay for trunk?
Segher
2017-07-18 Segher Boessenkool <seg...@kernel.crashing.org>
PR rtl-optimization/81423
* simplify-rtx.c (simplify_truncation): Handle truncating an IOR
with a constant that is -1 in the truncated to mode.
---
gcc/simplify-rtx.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 3bce329..ef41479 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -857,6 +857,15 @@ simplify_truncation (machine_mode mode, rtx op,
return simplify_gen_unary (TRUNCATE, mode, XEXP (op, 0),
GET_MODE (XEXP (op, 0)));
+ /* (truncate:A (ior X C)) is (const_int -1) if C is equal to that already,
+ in mode A. */
+ if (GET_CODE (op) == IOR
+ && SCALAR_INT_MODE_P (mode)
+ && SCALAR_INT_MODE_P (op_mode)
+ && CONST_INT_P (XEXP (op, 1))
+ && trunc_int_for_mode (INTVAL (XEXP (op, 1)), mode) == -1)
+ return constm1_rtx;
+
return NULL_RTX;
}
--
1.9.3
