This case is covered by Wilco's previous reply:

-----Original Message-----
From: Richard Kenner [] 
Sent: Tuesday, August 8, 2017 5:13 AM
To: Michael Collison <>
Cc:; nd <>;
Subject: RE: [PATCH] [Aarch64] Optimize subtract in shift counts

> The pattern will only be matched if the value is positive. More 
> specifically if the constant value is 32 (SImode) or 64 (DImode).

I don't mean the constant, but the value subtracted from it.
If that's negative, then we have a shift count larger than the wordsize.

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