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

[DAGCombiner] Fold extract_subvector of undef to undef. Fold away inserting undef subvectors. 

llvm-svn: 293152
This commit is contained in:
Craig Topper 2017-01-26 05:38:46 +00:00
parent b6122122c9
commit 001aad7da7
1 changed files with 8 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -13880,6 +13880,10 @@ SDValue DAGCombiner::visitEXTRACT_SUBVECTOR(SDNode* N) {
EVT NVT = N->getValueType(0);
SDValue V = N->getOperand(0);
// Extract from UNDEF is UNDEF.
if (V.isUndef())
return DAG.getUNDEF(NVT);
if (V->getOpcode() == ISD::CONCAT_VECTORS) {
// Combine:
// (extract_subvec (concat V1, V2, ...), i)
@ -14522,6 +14526,10 @@ SDValue DAGCombiner::visitINSERT_SUBVECTOR(SDNode *N) {
SDValue N1 = N->getOperand(1);
SDValue N2 = N->getOperand(2);
// If inserting an UNDEF, just return the original vector.
if (N1.isUndef())
return N0;
// Combine INSERT_SUBVECTORs where we are inserting to the same index.
// INSERT_SUBVECTOR( INSERT_SUBVECTOR( Vec, SubOld, Idx ), SubNew, Idx )
// --> INSERT_SUBVECTOR( Vec, SubNew, Idx )