Correct. It is truncated for integer shift, but not simd shift instructions. We 
generate a pattern in the split that only generates the integer shift 

-----Original Message-----
From: Richard Kenner [] 
Sent: Tuesday, August 8, 2017 1:04 PM
To: Michael Collison <>
Cc:; nd <>;
Subject: RE: [PATCH] [Aarch64] Optimize subtract in shift counts

> Because for integer shift instructions the shift count is truncated. 
> We ensure that we only use integer shift instructions by emitting a 
> shift with a mask. This only matches integer shift instructions in the 
> md file.

That's why I asked about SHIFT_COUNT_TRUNCATED.  So it's truncated for some 
shifts, but not all?

Reply via email to