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Improve DeSSA for InsertValue

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For aliasing InsertValue, allow number of indices up to 2.
This is mainly for layout struct that can have at most 2 indices.
This commit is contained in:
Gu, Junjie
2023-12-09 18:25:53 +00:00
committed by igcbot
parent 98c4ff610a
commit 89169e2dce
1 changed files with 29 additions and 13 deletions
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42
IGC/Compiler/CISACodeGen/DeSSA.cpp
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@ -1365,20 +1365,35 @@ void DeSSA::coalesceAliasInsertValue(InsertValueInst* theIVI)
}
};
// Get all fields' index if there are only one-level fields
auto getIndex = [](DenseSet<int>& aFields, SmallVector<Value*, 8>& IVIs)
// Get all fields' indices if there are at most 2 level fields.
// Using int = <i16 level_1-ix, i16 level_0-ix> to represent two
// level indices.
auto getIndices = [](DenseSet<int>& aFields, SmallVector<Value*, 8>& IVIs)
{
int nelts = (int)IVIs.size();
for (int i = 0; i < nelts; ++i)
{
InsertValueInst* tI = cast<InsertValueInst>(IVIs[i]);
if (tI->getNumIndices() != 1)
switch (tI->getNumIndices()) {
case 1:
{
uint16_t ix = (uint16_t)tI->getIndices().front();
aFields.insert((int)ix);
break;
}
case 2:
{
ArrayRef<unsigned> ids = tI->getIndices();
uint16_t lvl0_ix = (uint16_t)ids[0];
uint16_t lvl1_ix = (uint16_t)ids[1];
uint32_t ix = ((lvl1_ix << 16) | lvl0_ix);
aFields.insert((int)ix);
break;
}
default:
aFields.clear();
return;
}
uint32_t ix = tI->getIndices().front();
aFields.insert((int)ix);
}
};
@ -1402,8 +1417,8 @@ void DeSSA::coalesceAliasInsertValue(InsertValueInst* theIVI)
// ...
// Vn = InsVal Vn-1, Sn,
// where all Vi, i=0, n-1 has a single use. This sequence is called
// InsertValueInst chain (IVI Chain). And they are set to alias each
// other. For this chain, V0 is called the root and Vn the lead.
// InsertValueInst chain (IVI Chain). And they (all Vi) are set to alias
// each other.
//
// Start finding IVI chains from an inst that cannot be an operand of
// the other InsertValueInst. It's possible to have several IVI chains.
@ -1426,11 +1441,12 @@ void DeSSA::coalesceAliasInsertValue(InsertValueInst* theIVI)
// Chain3 Chain4
//
// The algorithm does the following:
// 1. Find all chains, within which all insts are aliased to each other.
// 1. Find all chains. All insts (Vs) of each chain are aliased to
// each other in the same chain.
// 2. Do aggressive aliasing : alias several chains along one path from
// root to a leaf node, assuming that no struct field is defined by
// more than one chains, which implies this can be applied if Root
// has undefValue as its operand like the following:
// root to a leaf node, as long as no struct field is defined by
// more than one chains, which is a strong condition and implies that
// the root inst should start like the followning:
// V0 = insval undef, s, 10
//
const Value* Oprd0 = theIVI->getOperand(0);
@ -1451,7 +1467,7 @@ void DeSSA::coalesceAliasInsertValue(InsertValueInst* theIVI)
Value* theAliasee = getAliasee(LeadInst);
if (isa<UndefValue>(Oprd0))
{
getIndex(commonFields, IVIChain);
getIndices(commonFields, IVIChain);
if (!commonFields.empty())
{ // Fields inserted are known, can do aggressive coalescing.
aggressiveAliasing = true;
@ -1482,7 +1498,7 @@ void DeSSA::coalesceAliasInsertValue(InsertValueInst* theIVI)
isChainUniform == WIA->isUniform(nextLead))
{
DenseSet<int> fields;
getIndex(fields, IVIChain);
getIndices(fields, IVIChain);
if (!fields.empty() &&
isDisjoin(commonFields, fields))
{