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Teach DAG combine to fold (trunc (fptoXi x)) to (fptoXi x)

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166049 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Liao 2012-10-16 19:38:35 +00:00
parent 6f7cccd2e2
commit 272ea03239
2 changed files with 64 additions and 0 deletions
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46
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -5308,6 +5308,52 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
if (Reduced.getNode())
return Reduced;
}
// fold (trunc (fptoXi x)) -> (smaller fptoXi x)
if ((N0.getOpcode() == ISD::FP_TO_UINT ||
N0.getOpcode() == ISD::FP_TO_SINT) && !LegalTypes)
return DAG.getNode(N0.getOpcode(), N->getDebugLoc(), VT, N0.getOperand(0));
// fold (trunc (concat ... x ...)) -> (concat ..., (trunc x), ...)),
// where ... are all 'undef'.
if (N0.getOpcode() == ISD::CONCAT_VECTORS && !LegalTypes) {
SmallVector<EVT, 8> VTs;
SDValue V;
unsigned Idx = 0;
unsigned NumDefs = 0;
for (unsigned i = 0, e = N0.getNumOperands(); i != e; ++i) {
SDValue X = N0.getOperand(i);
if (X.getOpcode() != ISD::UNDEF) {
V = X;
Idx = i;
NumDefs++;
}
// Stop if more than one members are non-undef.
if (NumDefs > 1)
break;
VTs.push_back(EVT::getVectorVT(*DAG.getContext(),
VT.getVectorElementType(),
X.getValueType().getVectorNumElements()));
}
if (NumDefs == 0)
return DAG.getUNDEF(VT);
if (NumDefs == 1) {
assert(V.getNode() && "The single defined operand is empty!");
SmallVector<SDValue, 8> Opnds;
for (unsigned i = 0, e = VTs.size(); i != e; ++i) {
if (i != Idx) {
Opnds.push_back(DAG.getUNDEF(VTs[i]));
continue;
}
SDValue NV = DAG.getNode(ISD::TRUNCATE, V.getDebugLoc(), VTs[i], V);
AddToWorkList(NV.getNode());
Opnds.push_back(NV);
}
return DAG.getNode(ISD::CONCAT_VECTORS, N->getDebugLoc(), VT,
&Opnds[0], Opnds.size());
}
}
// Simplify the operands using demanded-bits information.
if (!VT.isVector() &&

18
test/CodeGen/X86/trunc-fp2int.ll Normal file
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@ -0,0 +1,18 @@
; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mcpu=corei7 | FileCheck %s
define <4 x i8> @bar(<4 x float> %in) nounwind readnone alwaysinline {
%1 = fptoui <4 x float> %in to <4 x i8>
ret <4 x i8> %1
; CHECK: bar
; CHECK: cvttps2dq
}
define <4 x i8> @foo(<4 x float> %in) nounwind readnone alwaysinline {
%1 = fptoui <4 x float> %in to <4 x i32>
%2 = trunc <4 x i32> %1 to <4 x i16>
%3 = shufflevector <4 x i16> %2, <4 x i16> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
%4 = trunc <8 x i16> %3 to <8 x i8>
%5 = shufflevector <8 x i8> %4, <8 x i8> undef, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
ret <4 x i8> %5
; CHECK: foo
; CHECK: cvttps2dq
}