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Fold trunc(any_ext). This gives stuff like:

Browse Source 
27,28c27
<       movzwl %di, %edi
<       movl %edi, %ebx
---
>       movw %di, %bx


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28137 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-05-05 22:56:26 +00:00
parent 06afe07037
commit b72773bb88
1 changed files with 2 additions and 1 deletions
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3
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -2005,7 +2005,8 @@ SDOperand DAGCombiner::visitTRUNCATE(SDNode *N) {
if (N0.getOpcode() == ISD::TRUNCATE)
return DAG.getNode(ISD::TRUNCATE, VT, N0.getOperand(0));
// fold (truncate (ext x)) -> (ext x) or (truncate x) or x
if (N0.getOpcode() == ISD::ZERO_EXTEND || N0.getOpcode() == ISD::SIGN_EXTEND){
if (N0.getOpcode() == ISD::ZERO_EXTEND || N0.getOpcode() == ISD::SIGN_EXTEND||
N0.getOpcode() == ISD::ANY_EXTEND) {
if (N0.getValueType() < VT)
// if the source is smaller than the dest, we still need an extend
return DAG.getNode(N0.getOpcode(), VT, N0.getOperand(0));