6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-07-18 10:24:45 +00:00
Code Issues Projects Releases Wiki Activity

SelectionDAG: Teach the legalizer to split SETCC if VSELECT needs splitting too.

Browse Source 
The Type Legalizer recognizes that VSELECT needs to be split, because the type
is to wide for the given target. The same does not always apply to SETCC,
because less space is required to encode the result of a comparison. As a result
VSELECT is split and SETCC is unrolled into scalar comparisons.

This commit fixes the issue by checking for VSELECT-SETCC patterns in the DAG
Combiner. If a matching pattern is found, then the result mask of SETCC is
promoted to the expected vector mask type for the given target. This mask has
usually the same size as the VSELECT return type (except for Intel KNL). Now the
type legalizer will split both VSELECT and SETCC.

This allows the following X86 DAG Combine code to sucessfully detect the MIN/MAX
pattern. This fixes PR16695, PR17002, and <rdar://problem/14594431>.

Reviewed by Nadav

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193676 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Juergen Ributzka
2013-10-30 05:48:18 +00:00
parent 6a4860af7a
commit 4eced19c50
4 changed files with 87 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@@ -4346,6 +4346,28 @@ SDValue DAGCombiner::visitVSELECT(SDNode *N) {
}
}
// Treat SETCC as a vector mask and promote the result type based on the
// targets expected SETCC result type. This will ensure that SETCC and VSELECT
// are both split by the type legalizer. This is done to prevent the type
// legalizer from unrolling SETCC into scalar comparions.
EVT SelectVT = N->getValueType(0);
EVT MaskVT = getSetCCResultType(SelectVT);
if (N0.getOpcode() == ISD::SETCC && N0.getValueType() != MaskVT) {
SDLoc MaskDL(N0);
// Extend the mask to the desired value type.
ISD::NodeType ExtendCode =
TargetLowering::getExtendForContent(TLI.getBooleanContents(true));
SDValue Mask = DAG.getNode(ExtendCode, MaskDL, MaskVT, N0);
AddToWorkList(Mask.getNode());
SDValue LHS = N->getOperand(1);
SDValue RHS = N->getOperand(2);
return DAG.getNode(ISD::VSELECT, DL, SelectVT, Mask, LHS, RHS);
}
return SDValue();
}