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515604
2016 Apr 11
2
X86 TRUNCATE cost for AVX & AVX2 mode
Hi,
I was going through the X86TTIImpl::getCastInstrCost, and got a doubt on cost
calculation for TRUNCATE instruction in AVX mode.
In AVX2ConversionTbl & AVXConversionTbl table there is no cost defined for
TRUNCATE v16i32 to v16i8, as a fallback it goes to SSE41ConversionTbl table and there
it finds cost as 30 for this operation. 30 cost for this operation looks very high.
Wondering why
2016 Apr 12
2
X86 TRUNCATE cost for AVX & AVX2 mode
...Ashutosh.Nema at amd.com>
Cc: llvm-dev <llvm-dev at lists.llvm.org>; Zuckerman, Michael <michael.zuckerman at intel.com>
Subject: RE: X86 TRUNCATE cost for AVX & AVX2 mode
Hi,
One day I worked hard and refactored the cost calculation for all X86 targets.
http://reviews.llvm.org/D15604
But this revision was not accepted.
I fixed conversions, but assume that truncation suffers from the same problem.
I used "SplitFactor" in order to process wide types.
I'll be happy if you'll try to reanimate this work or part of it, because the huge numbers causes a non-optimal...