maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[DAGCombiner] restrict store merge of truncs to early combining 

The pattern matching does not account for truncating stores,
so it is unlikely to work at later stages. So we are likely
wasting compile-time with no hope of improvement by running
this later.
This commit is contained in:
Sanjay Patel 2020-08-23 08:36:46 -04:00
parent 55208f5a21
commit 1d0fa79824
1 changed files with 13 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -6856,6 +6856,14 @@ static SDValue stripTruncAndExt(SDValue Value) {
/// =>
/// *((i32)p) = BSWAP(val);
SDValue DAGCombiner::mergeTruncStores(StoreSDNode *N) {
// The matching looks for "store (trunc x)" patterns that appear early but are
// likely to be replaced by truncating store nodes during combining.
// TODO: If there is evidence that running this later would help, this
// limitation could be removed. Legality checks may need to be added
// for the created store and optional bswap/rotate.
if (LegalOperations)
return SDValue();
// Collect all the stores in the chain.
SDValue Chain;
SmallVector<StoreSDNode *, 8> Stores;
@ -6880,9 +6888,6 @@ SDValue DAGCombiner::mergeTruncStores(StoreSDNode *N) {
if (WideVT != MVT::i16 && WideVT != MVT::i32 && WideVT != MVT::i64)
return SDValue();
if (LegalOperations && !TLI.isOperationLegal(ISD::STORE, WideVT))
return SDValue();
// Check if all bytes of the source value that we are looking at are stored
// to the same base address. Collect offsets from Base address into OffsetMap.
SDValue SourceValue;
@ -6960,16 +6965,8 @@ SDValue DAGCombiner::mergeTruncStores(StoreSDNode *N) {
if (!IsBigEndian.hasValue())
return SDValue();
// If the store needs byte swap check if the target supports it.
// Before legalize we can introduce illegal bswaps which will be later
// converted to an explicit bswap sequence. This way we end up with a single
// store and byte shuffling instead of several stores and byte shuffling.
const DataLayout &Layout = DAG.getDataLayout();
bool NeedBswap = Layout.isBigEndian() != *IsBigEndian;
if (NeedBswap && LegalOperations && !TLI.isOperationLegal(ISD::BSWAP, WideVT))
return SDValue();
// Check that a store of the wide type is both allowed and fast on the target
const DataLayout &Layout = DAG.getDataLayout();
bool Fast = false;
bool Allowed = TLI.allowsMemoryAccess(Context, Layout, WideVT,
*FirstStore->getMemOperand(), &Fast);
@ -6983,6 +6980,10 @@ SDValue DAGCombiner::mergeTruncStores(StoreSDNode *N) {
SourceValue = DAG.getNode(ISD::TRUNCATE, DL, WideVT, SourceValue);
}
// Before legalize we can introduce illegal bswaps which will be later
// converted to an explicit bswap sequence. This way we end up with a single
// store and byte shuffling instead of several stores and byte shuffling.
bool NeedBswap = Layout.isBigEndian() != *IsBigEndian;
if (NeedBswap)
SourceValue = DAG.getNode(ISD::BSWAP, DL, WideVT, SourceValue);