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Generalize ExtendUsesToFormExtLoad to be usable for ANY_EXTEND,

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in addition to ZERO_EXTEND and SIGN_EXTEND. Fix a bug in the
way it checked for live-out values, and simplify the way it
find users by using SDNode::use_iterator's (relatively) new
features. Also, make it slightly more permissive on targets
with free truncates.

In SelectionDAGBuild, avoid creating ANY_EXTEND nodes that are
larger than necessary. If the target's SwitchAmountTy has
enough bits, use it. This exposes the truncate to optimization
early, enabling more optimizations.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@68670 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-04-09 03:51:29 +00:00
parent 7d770be047
commit 57fc82d409
5 changed files with 159 additions and 85 deletions
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lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
+18 -2
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@@ -2190,8 +2190,24 @@ void SelectionDAGLowering::visitBinary(User &I, unsigned OpCode) {
void SelectionDAGLowering::visitShift(User &I, unsigned Opcode) {
SDValue Op1 = getValue(I.getOperand(0));
SDValue Op2 = getValue(I.getOperand(1));
if (!isa<VectorType>(I.getType())) {
if (TLI.getPointerTy().bitsLT(Op2.getValueType()))
if (!isa<VectorType>(I.getType()) &&
Op2.getValueType() != TLI.getShiftAmountTy()) {
// If the operand is smaller than the shift count type, promote it.
if (TLI.getShiftAmountTy().bitsGT(Op2.getValueType()))
Op2 = DAG.getNode(ISD::ANY_EXTEND, getCurDebugLoc(),
TLI.getShiftAmountTy(), Op2);
// If the operand is larger than the shift count type but the shift
// count type has enough bits to represent any shift value, truncate
// it now. This is a common case and it exposes the truncate to
// optimization early.
else if (TLI.getShiftAmountTy().getSizeInBits() >=
Log2_32_Ceil(Op2.getValueType().getSizeInBits()))
Op2 = DAG.getNode(ISD::TRUNCATE, getCurDebugLoc(),
TLI.getShiftAmountTy(), Op2);
// Otherwise we'll need to temporarily settle for some other
// convenient type; type legalization will make adjustments as
// needed.
else if (TLI.getPointerTy().bitsLT(Op2.getValueType()))
Op2 = DAG.getNode(ISD::TRUNCATE, getCurDebugLoc(),
TLI.getPointerTy(), Op2);
else if (TLI.getPointerTy().bitsGT(Op2.getValueType()))