Subzero: Clean up live range construction.
Moves the deletion of newly dead instructions into the main liveness() routine. The old livenessPostProcess() routine is renamed and now used purely for live range construction.
The hack is removed in which live in-args have a custom live range segment added to avoid an artifact of the live ranges. It is replaced with a gentler hack that extends the instruction numbering range of the initial basic block to avoid the artifact.
Since special live range segments no longer need to be prepended, the live range representation is simplified and we can always assume that segments are being appended, never prepended (and as before, never added to the middle).
Some magic constants involving special instruction numbers are replaced with symbolic constants.
BUG= none
R=jvoung@chromium.org
Review URL: https://codereview.chromium.org/802003003
diff --git a/src/IceCfgNode.cpp b/src/IceCfgNode.cpp
index 1623731..42731ad 100644
--- a/src/IceCfgNode.cpp
+++ b/src/IceCfgNode.cpp
@@ -639,40 +639,16 @@
return Changed;
}
-// Now that basic liveness is complete, remove dead instructions that
-// were tentatively marked as dead, and compute actual live ranges.
-// It is assumed that within a single basic block, a live range begins
-// at most once and ends at most once. This is certainly true for
-// pure SSA form. It is also true once phis are lowered, since each
+// Once basic liveness is complete, compute actual live ranges. It is
+// assumed that within a single basic block, a live range begins at
+// most once and ends at most once. This is certainly true for pure
+// SSA form. It is also true once phis are lowered, since each
// assignment to the phi-based temporary is in a different basic
// block, and there is a single read that ends the live in the basic
// block that contained the actual phi instruction.
-void CfgNode::livenessPostprocess(LivenessMode Mode, Liveness *Liveness) {
- InstNumberT FirstInstNum = Inst::NumberSentinel;
- InstNumberT LastInstNum = Inst::NumberSentinel;
- // Process phis in any order. Process only Dest operands.
- for (auto I = Phis.begin(), E = Phis.end(); I != E; ++I) {
- I->deleteIfDead();
- if (I->isDeleted())
- continue;
- if (FirstInstNum == Inst::NumberSentinel)
- FirstInstNum = I->getNumber();
- assert(I->getNumber() > LastInstNum);
- LastInstNum = I->getNumber();
- }
- // Process instructions
- for (auto I = Insts.begin(), E = Insts.end(); I != E; ++I) {
- I->deleteIfDead();
- if (I->isDeleted())
- continue;
- if (FirstInstNum == Inst::NumberSentinel)
- FirstInstNum = I->getNumber();
- assert(I->getNumber() > LastInstNum);
- LastInstNum = I->getNumber();
- }
- if (Mode != Liveness_Intervals)
- return;
- TimerMarker T1(TimerStack::TT_liveRangeCtor, Func);
+void CfgNode::livenessAddIntervals(Liveness *Liveness, InstNumberT FirstInstNum,
+ InstNumberT LastInstNum) {
+ TimerMarker T1(TimerStack::TT_liveRange, Func);
SizeT NumVars = Liveness->getNumVarsInNode(this);
LivenessBV &LiveIn = Liveness->getLiveIn(this);
