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C++: Hide away the 'multiply by two' hack in a predicate.

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Mathias Vorreiter Pedersen
2024-07-01 18:48:10 +01:00
parent 8db7ece8d4
commit cf8b2d55c5
1 changed files with 15 additions and 6 deletions
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21
cpp/ql/lib/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll
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@@ -697,6 +697,14 @@ private import DefUse
* potentially very sparse.
*/
module DefUse {
bindingset[index, block]
pragma[inline_late]
private int getNonChiOffset(int index, OldBlock block) { result = 2 * index }
bindingset[index, block]
pragma[inline_late]
private int getChiOffset(int index, OldBlock block) { result = getNonChiOffset(index, block) + 1 }
/**
* Gets the `Instruction` for the definition at offset `defOffset` in block `defBlock`.
*/
@@ -709,7 +717,7 @@ module DefUse {
oldOffset >= 0
|
// An odd offset corresponds to the `Chi` instruction.
defOffset = oldOffset * 2 + 1 and
defOffset = getChiOffset(oldOffset, defBlock) and
result = getChi(oldInstr) and
(
defLocation = Alias::getResultMemoryLocation(oldInstr) or
@@ -718,7 +726,7 @@ module DefUse {
actualDefLocation = defLocation.getVirtualVariable()
or
// An even offset corresponds to the original instruction.
defOffset = oldOffset * 2 and
defOffset = getNonChiOffset(oldOffset, defBlock) and
result = getNewInstruction(oldInstr) and
(
defLocation = Alias::getResultMemoryLocation(oldInstr) or
@@ -871,8 +879,8 @@ module DefUse {
block.getInstruction(index) = def and
overlap = Alias::getOverlap(defLocation, useLocation) and
if overlap instanceof MayPartiallyOverlap
then offset = (index * 2) + 1 // The use will be connected to the definition on the `Chi` instruction.
else offset = index * 2 // The use will be connected to the definition on the original instruction.
then offset = getChiOffset(index, block) // The use will be connected to the definition on the `Chi` instruction.
else offset = getNonChiOffset(index, block) // The use will be connected to the definition on the original instruction.
)
}
@@ -933,10 +941,11 @@ module DefUse {
block.getInstruction(index) = use and
(
// A direct use of the location.
useLocation = Alias::getOperandMemoryLocation(use.getAnOperand()) and offset = index * 2
useLocation = Alias::getOperandMemoryLocation(use.getAnOperand()) and
offset = getNonChiOffset(index, block)
or
// A `Chi` instruction will include a use of the virtual variable.
hasChiNode(useLocation, use) and offset = (index * 2) + 1
hasChiNode(useLocation, use) and offset = getChiOffset(index, block)
)
)
}