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Refine fix to bug 15041. 

Thanks to help from Nadav and Hal, I have a more reasonable (and even
correct!) approach.  This specifically penalizes the insertelement
and extractelement operations for the performance hit that will occur
on PowerPC processors.

llvm-svn: 174725
This commit is contained in:
Bill Schmidt 2013-02-08 18:19:17 +00:00
parent 22d275f7b8
commit 62fe7a5b17
2 changed files with 31 additions and 16 deletions
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31
llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
View File

@ -194,24 +194,23 @@ unsigned PPCTTI::getVectorInstrCost(unsigned Opcode, Type *Val,
unsigned Index) const {
assert(Val->isVectorTy() && "This must be a vector type");
const unsigned Awful = 1000;
int ISD = TLI->InstructionOpcodeToISD(Opcode);
assert(ISD && "Invalid opcode");
// Vector element insert/extract with Altivec is very expensive.
// Until VSX is available, avoid vectorizing loops that require
// these operations.
if (Opcode == ISD::EXTRACT_VECTOR_ELT ||
Opcode == ISD::INSERT_VECTOR_ELT)
return Awful;
// Estimated cost of a load-hit-store delay. This was obtained
// experimentally as a minimum needed to prevent unprofitable
// vectorization for the paq8p benchmark. It may need to be
// raised further if other unprofitable cases remain.
unsigned LHSPenalty = 12;
// We don't vectorize SREM/UREM so well. Constrain the vectorizer
// for those as well.
if (Opcode == ISD::SREM || Opcode == ISD::UREM)
return Awful;
// VSELECT is not yet implemented, leading to use of insert/extract
// and ISEL, hence not a good idea.
if (Opcode == ISD::VSELECT)
return Awful;
// Vector element insert/extract with Altivec is very expensive,
// because they require store and reload with the attendant
// processor stall for load-hit-store. Until VSX is available,
// these need to be estimated as very costly.
if (ISD == ISD::EXTRACT_VECTOR_ELT ||
ISD == ISD::INSERT_VECTOR_ELT)
return LHSPenalty +
TargetTransformInfo::getVectorInstrCost(Opcode, Val, Index);
return TargetTransformInfo::getVectorInstrCost(Opcode, Val, Index);
}

16
llvm/test/Analysis/CostModel/PowerPC/insert_extract.ll Normal file
View File

@ -0,0 +1,16 @@
; RUN: opt < %s -cost-model -analyze -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 | FileCheck %s
target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
target triple = "powerpc64-unknown-linux-gnu"
define i32 @insert(i32 %arg) {
; CHECK: cost of 13 {{.*}} insertelement
%x = insertelement <4 x i32> undef, i32 %arg, i32 0
ret i32 undef
}
define i32 @extract(<4 x i32> %arg) {
; CHECK: cost of 13 {{.*}} extractelement
%x = extractelement <4 x i32> %arg, i32 0
ret i32 %x
}