[llvm-commits] [llvm] r119728 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/X86/2010-11-18-SelectOfExtload.ll
Frits van Bommel
fvbommel at gmail.com
Thu Nov 18 12:41:45 PST 2010
On Thu, Nov 18, 2010 at 9:05 PM, Duncan Sands <baldrick at free.fr> wrote:
> Author: baldrick
> Date: Thu Nov 18 14:05:18 2010
> New Revision: 119728
> URL: http://llvm.org/viewvc/llvm-project?rev=119728&view=rev
> The DAGCombiner was threading select over pairs of extending loads even
> if the extension types were not the same. The result was that if you
> fed a select with sext and zext loads, as in the testcase, then it
> would get turned into a zext (or sext) of the select, which is wrong
> in the cases when it should have been an sext (resp. zext). Reported
> and diagnosed by Sebastien Deldon.
> + // If this is an EXTLOAD, the kind of extension must match.
> + (LLD->getExtensionType() != RLD->getExtensionType() &&
> + // The only exception is if one of the extensions is anyext.
> + LLD->getExtensionType() != ISD::EXTLOAD &&
> + RLD->getExtensionType() != ISD::EXTLOAD) ||
This looked funny to me, so I checked the rest of the function. Later
on, there's this code:
Load = DAG.getExtLoad(LLD->getExtensionType(), // ...
Shouldn't this be changed to something like
Load = DAG.getExtLoad((LLD->getExtensionType() != ISD::EXTLOAD ?
LLD->getExtensionType() : RLD->getExtensionType()), // ...
It looks to me like it could now still turn e.g. (select %cond (anyext
%a) (sext %b)) into (anyext (select %cond %a %b)) which it probably
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