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Add a BlockInfo::FirstDef field. 

This is either an invalid SlotIndex, or valno->def for the first value
defined inside the block. PHI values are not counted as defined inside
the block.

The FirstDef field will be used when estimating the cost of spilling
around a block.

llvm-svn: 136736
This commit is contained in:
Jakob Stoklund Olesen 2011-08-02 22:37:22 +00:00
parent f047ff4fe1
commit ae8027cc95
2 changed files with 15 additions and 1 deletions
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15
llvm/lib/CodeGen/SplitKit.cpp
View File

@ -188,6 +188,13 @@ bool SplitAnalysis::calcLiveBlockInfo() {
// LVI is the first live segment overlapping MBB.
BI.LiveIn = LVI->start <= Start;
// When not live in, the first use should be a def.
if (!BI.LiveIn) {
assert(LVI->start == LVI->valno->def && "Dangling LiveRange start");
assert(LVI->start == BI.FirstUse && "First instr should be a def");
BI.FirstDef = BI.FirstUse;
}
// Look for gaps in the live range.
BI.LiveOut = true;
while (LVI->end < Stop) {
@ -197,6 +204,7 @@ bool SplitAnalysis::calcLiveBlockInfo() {
BI.LastUse = LastStop;
break;
}
if (LastStop < LVI->start) {
// There is a gap in the live range. Create duplicate entries for the
// live-in snippet and the live-out snippet.
@ -210,8 +218,13 @@ bool SplitAnalysis::calcLiveBlockInfo() {
// Set up BI for the live-out part.
BI.LiveIn = false;
BI.LiveOut = true;
BI.FirstUse = LVI->start;
BI.FirstUse = BI.FirstDef = LVI->start;
}
// A LiveRange that starts in the middle of the block must be a def.
assert(LVI->start == LVI->valno->def && "Dangling LiveRange start");
if (!BI.FirstDef)
BI.FirstDef = LVI->start;
}
UseBlocks.push_back(BI);

1
llvm/lib/CodeGen/SplitKit.h
View File

@ -78,6 +78,7 @@ public:
MachineBasicBlock *MBB;
SlotIndex FirstUse; ///< First instr using current reg.
SlotIndex LastUse; ///< Last instr using current reg.
SlotIndex FirstDef; ///< First non-phi valno->def, or SlotIndex().
bool LiveIn; ///< Current reg is live in.
bool LiveOut; ///< Current reg is live out.