On Thu, Oct 14, 2021 at 11:06 AM Andrew MacLeod via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> As the PR observes, if the first operand of a right shift is 0 or -1,
> operand 2 doesn't matter and the result will be the same as op1, so it
> can be turned into a copy.
>
> This patch checks for that condition and performs the operation in EVRP.
>
> Bootstrapped on x86_64-pc-linux-gnu with no regressions. Pushed.
>
> Andrew
>
/* PR tree-optimization/102738 */
+/* { dg-options "-O2 -fdump-tree-evrp" } */
+
+/* Remove arithmetic shift right when the LHS is known to be 0 or -1. */
+
+int a1(__int128 f, int g)
Missing
/* { dg-do compile { target int128 } } */
--
H.J.
