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authorNikita Popov <npopov@redhat.com>2024-03-20 10:59:45 +0100
committerGitHub <noreply@github.com>2024-03-20 10:59:45 +0100
commit0f46e31cfbf415fcd3d3ce121bef94e92c6ccfc8 (patch)
treef7480770f05cd77458340f1f23104275c9be1614 /llvm/lib/IR/Operator.cpp
parent1f63a56cede85bcd5f4fea3663bd3a47b801a396 (diff)
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[IR] Change representation of getelementptr inrange (#84341)
As part of the migration to ptradd (https://discourse.llvm.org/t/rfc-replacing-getelementptr-with-ptradd/68699), we need to change the representation of the `inrange` attribute, which is used for vtable splitting. Currently, inrange is specified as follows: ``` getelementptr inbounds ({ [4 x ptr], [4 x ptr] }, ptr @vt, i64 0, inrange i32 1, i64 2) ``` The `inrange` is placed on a GEP index, and all accesses must be "in range" of that index. The new representation is as follows: ``` getelementptr inbounds inrange(-16, 16) ({ [4 x ptr], [4 x ptr] }, ptr @vt, i64 0, i32 1, i64 2) ``` This specifies which offsets are "in range" of the GEP result. The new representation will continue working when canonicalizing to ptradd representation: ``` getelementptr inbounds inrange(-16, 16) (i8, ptr @vt, i64 48) ``` The inrange offsets are relative to the return value of the GEP. An alternative design could make them relative to the source pointer instead. The result-relative format was chosen on the off-chance that we want to extend support to non-constant GEPs in the future, in which case this variant is more expressive. This implementation "upgrades" the old inrange representation in bitcode by simply dropping it. This is a very niche feature, and I don't think trying to upgrade it is worthwhile. Let me know if you disagree.
Diffstat (limited to 'llvm/lib/IR/Operator.cpp')
-rw-r--r--llvm/lib/IR/Operator.cpp8
1 files changed, 7 insertions, 1 deletions
diff --git a/llvm/lib/IR/Operator.cpp b/llvm/lib/IR/Operator.cpp
index caf8fe6..b9cd219 100644
--- a/llvm/lib/IR/Operator.cpp
+++ b/llvm/lib/IR/Operator.cpp
@@ -37,7 +37,7 @@ bool Operator::hasPoisonGeneratingFlags() const {
case Instruction::GetElementPtr: {
auto *GEP = cast<GEPOperator>(this);
// Note: inrange exists on constexpr only
- return GEP->isInBounds() || GEP->getInRangeIndex() != std::nullopt;
+ return GEP->isInBounds() || GEP->getInRange() != std::nullopt;
}
case Instruction::ZExt:
if (auto *NNI = dyn_cast<PossiblyNonNegInst>(this))
@@ -69,6 +69,12 @@ Type *GEPOperator::getResultElementType() const {
return cast<GetElementPtrConstantExpr>(this)->getResultElementType();
}
+std::optional<ConstantRange> GEPOperator::getInRange() const {
+ if (auto *CE = dyn_cast<GetElementPtrConstantExpr>(this))
+ return CE->getInRange();
+ return std::nullopt;
+}
+
Align GEPOperator::getMaxPreservedAlignment(const DataLayout &DL) const {
/// compute the worse possible offset for every level of the GEP et accumulate
/// the minimum alignment into Result.