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Clear lower half of two-slot value when upper half is not live #157

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Oct 26, 2020
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Clear lower half of two-slot value when upper half is not live #157

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15 changes: 13 additions & 2 deletions compiler/src/org.graalvm.compiler.java/src/org/graalvm/compiler/java/FrameStateBuilder.java
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Original file line number Diff line number Diff line change
Expand Up @@ -659,14 +659,25 @@ public void clearNonLiveLocals(BciBlock block, LocalLiveness liveness, boolean l
if (liveIn) {
for (int i = 0; i < locals.length; i++) {
if (!liveness.localIsLiveIn(block, i)) {
assert locals[i] != TWO_SLOT_MARKER || locals[i - 1] == null : "Clearing of second slot must have cleared the first slot too";
if (locals[i] == TWO_SLOT_MARKER) {
/*
* Clearing a slot is equivalent to a storeLocal() of that slot: if the old
* value is the upper half of a two-slot value, both slots need to be
* cleared. The liveness analysis cannot detect these cases and also mark
* the previous slot as non-live because at the beginning / end of the block
* the slot at index i - 1 can be occupied by a live single-slot value.
*/
locals[i - 1] = null;
}
locals[i] = null;
}
}
} else {
for (int i = 0; i < locals.length; i++) {
if (!liveness.localIsLiveOut(block, i)) {
assert locals[i] != TWO_SLOT_MARKER || locals[i - 1] == null : "Clearing of second slot must have cleared the first slot too";
if (locals[i] == TWO_SLOT_MARKER) {
locals[i - 1] = null;
}
locals[i] = null;
}
}
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