[clang][bytecode] Handle __builtin_bcmp #119678
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... the same as `__builtin_memcmp`. Also fix a bug we still had when we couldn't find a difference in the two inputs after `Size` bytes.
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@llvm/pr-subscribers-clang Author: Timm Baeder (tbaederr) Changes... the same as Full diff: https://github.com/llvm/llvm-project/pull/119678.diff 2 Files Affected:
diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index a343280b5ce50f..21baedf832eeac 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -1917,7 +1917,7 @@ static bool interp__builtin_memcmp(InterpState &S, CodePtr OpPC,
const APSInt &Size =
peekToAPSInt(S.Stk, *S.getContext().classify(Call->getArg(2)));
- if (ID == Builtin::BImemcmp)
+ if (ID == Builtin::BImemcmp || ID == Builtin::BIbcmp)
diagnoseNonConstexprBuiltin(S, OpPC, ID);
if (Size.isZero()) {
@@ -1952,15 +1952,34 @@ static bool interp__builtin_memcmp(InterpState &S, CodePtr OpPC,
BufferB.byteSize().getQuantity());
size_t CmpSize =
std::min(MinBufferSize, static_cast<size_t>(Size.getZExtValue()));
- int Result = std::memcmp(BufferA.Data.get(), BufferB.Data.get(), CmpSize);
- if (Result == 0)
+
+ for (size_t I = 0; I != CmpSize; ++I) {
+ std::byte A = BufferA.Data[I];
+ std::byte B = BufferB.Data[I];
+
+ if (A < B) {
+ pushInteger(S, -1, Call->getType());
+ return true;
+ } else if (A > B) {
+ pushInteger(S, 1, Call->getType());
+ return true;
+ }
+ }
+
+ // We compared CmpSize bytes above. If the limiting factor was the Size
+ // passed, we're done and the result is equality (0).
+ if (Size.getZExtValue() <= CmpSize) {
pushInteger(S, 0, Call->getType());
- else if (Result < 0)
- pushInteger(S, -1, Call->getType());
- else
- pushInteger(S, 1, Call->getType());
+ return true;
+ }
- return true;
+ // However, if we read all the available bytes but were instructed to read
+ // even more, diagnose this as a "read of dereferenced one-past-the-end
+ // pointer". This is what would happen if we called CheckRead() on every array
+ // element.
+ S.FFDiag(S.Current->getSource(OpPC), diag::note_constexpr_access_past_end)
+ << AK_Read << S.Current->getRange(OpPC);
+ return false;
}
bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
@@ -2438,6 +2457,8 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
case Builtin::BI__builtin_memcmp:
case Builtin::BImemcmp:
+ case Builtin::BI__builtin_bcmp:
+ case Builtin::BIbcmp:
if (!interp__builtin_memcmp(S, OpPC, Frame, F, Call))
return false;
break;
diff --git a/clang/test/AST/ByteCode/builtin-functions.cpp b/clang/test/AST/ByteCode/builtin-functions.cpp
index 83caa1d03df3a3..4ee24646286fa8 100644
--- a/clang/test/AST/ByteCode/builtin-functions.cpp
+++ b/clang/test/AST/ByteCode/builtin-functions.cpp
@@ -1255,4 +1255,19 @@ namespace Memcmp {
// both-note {{not supported}}
static_assert(__builtin_memcmp("", &incomplete, 1u) == 42); // both-error {{not an integral constant}} \
// both-note {{not supported}}
+
+ static_assert(__builtin_memcmp(u8"abab\0banana", u8"abab\0banana", 100) == 0); // both-error {{not an integral constant}} \
+ // both-note {{dereferenced one-past-the-end}}
+
+ static_assert(__builtin_bcmp("abaa", "abba", 3) != 0);
+ static_assert(__builtin_bcmp("abaa", "abba", 2) == 0);
+ static_assert(__builtin_bcmp("a\203", "a", 2) != 0);
+ static_assert(__builtin_bcmp("a\203", "a\003", 2) != 0);
+ static_assert(__builtin_bcmp(0, 0, 0) == 0);
+ static_assert(__builtin_bcmp("abab\0banana", "abab\0banana", 100) == 0); // both-error {{not an integral constant}}\
+ // both-note {{dereferenced one-past-the-end}}
+ static_assert(__builtin_bcmp("abab\0banana", "abab\0canada", 100) != 0); // FIXME: Should we reject this?
+ static_assert(__builtin_bcmp("abab\0banana", "abab\0canada", 7) != 0);
+ static_assert(__builtin_bcmp("abab\0banana", "abab\0canada", 6) != 0);
+ static_assert(__builtin_bcmp("abab\0banana", "abab\0canada", 5) == 0);
}
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/73/builds/10145 Here is the relevant piece of the build log for the reference |
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Check out https://lab.llvm.org/buildbot/#/builders/13/builds/4041: |
tbaederr
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to tbaederr/llvm-project
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Dec 13, 2024
See the discussion in llvm#119678 (comment) and llvm#119544 (comment)
tbaederr
added a commit
that referenced
this pull request
Dec 13, 2024
See the discussion in #119678 (comment) and #119544 (comment)
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... the same as
__builtin_memcmp. Also fix a bug we still had when we couldn't find a difference in the two inputs afterSizebytes.