[PATCH] D90637: [ValueTracking] Inbounds does not imply nsw
Nikita Popov via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Nov 13 08:58:32 PST 2020
This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG92b708902e1d: [ValueTracking] Don't set nsw flag for inbounds addition (authored by nikic).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D90637/new/
https://reviews.llvm.org/D90637
Files:
llvm/lib/Analysis/ValueTracking.cpp
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -1289,9 +1289,6 @@
APInt AccConstIndices(BitWidth, 0, /*IsSigned*/ true);
gep_type_iterator GTI = gep_type_begin(I);
- // If the inbounds keyword is not present, the offsets are added to the
- // base address with silently-wrapping two’s complement arithmetic.
- bool IsInBounds = cast<GEPOperator>(I)->isInBounds();
for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) {
// TrailZ can only become smaller, short-circuit if we hit zero.
if (Known.isUnknown())
@@ -1356,17 +1353,17 @@
// to the width of the pointer.
IndexBits = IndexBits.sextOrTrunc(BitWidth);
+ // Note that inbounds does *not* guarantee nsw for the addition, as only
+ // the offset is signed, while the base address is unsigned.
Known = KnownBits::computeForAddSub(
- /*Add=*/true,
- /*NSW=*/IsInBounds, Known, IndexBits);
+ /*Add=*/true, /*NSW=*/false, Known, IndexBits);
}
if (!Known.isUnknown() && !AccConstIndices.isNullValue()) {
KnownBits Index(BitWidth);
Index.Zero = ~AccConstIndices;
Index.One = AccConstIndices;
Known = KnownBits::computeForAddSub(
- /*Add=*/true,
- /*NSW=*/IsInBounds, Known, Index);
+ /*Add=*/true, /*NSW=*/false, Known, Index);
}
break;
}
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D90637.305178.patch
Type: text/x-patch
Size: 1526 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20201113/094d1581/attachment.bin>
More information about the llvm-commits
mailing list