[clang][bytecode] Handle __builtin_memcmp

[tbaederr]

No description provided.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/119544.diff

2 Files Affected:

• (modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+30-3)
• (modified) clang/test/AST/ByteCode/builtin-functions.cpp (+21)

diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index a0de193ec32a2f..a567a955bb536f 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -190,6 +190,12 @@ static bool interp__builtin_is_constant_evaluated(InterpState &S, CodePtr OpPC,
   return true;
 }
 
+/// Determine if T is a character type for which we guarantee that
+/// sizeof(T) == 1.
+static bool isOneByteCharacterType(QualType T) {
+  return T->isCharType() || T->isChar8Type();
+}
+
 static bool interp__builtin_strcmp(InterpState &S, CodePtr OpPC,
                                    const InterpFrame *Frame,
                                    const Function *Func, const CallExpr *Call) {
@@ -197,11 +203,13 @@ static bool interp__builtin_strcmp(InterpState &S, CodePtr OpPC,
   const Pointer &A = getParam<Pointer>(Frame, 0);
   const Pointer &B = getParam<Pointer>(Frame, 1);
 
-  if (ID == Builtin::BIstrcmp || ID == Builtin::BIstrncmp)
+  if (ID == Builtin::BIstrcmp || ID == Builtin::BIstrncmp ||
+      ID == Builtin::BImemcmp)
     diagnoseNonConstexprBuiltin(S, OpPC, ID);
 
   uint64_t Limit = ~static_cast<uint64_t>(0);
-  if (ID == Builtin::BIstrncmp || ID == Builtin::BI__builtin_strncmp)
+  if (ID == Builtin::BIstrncmp || ID == Builtin::BI__builtin_strncmp ||
+      ID == Builtin::BI__builtin_memcmp || ID == Builtin::BImemcmp)
     Limit = peekToAPSInt(S.Stk, *S.getContext().classify(Call->getArg(2)))
                 .getZExtValue();
 
@@ -219,6 +227,23 @@ static bool interp__builtin_strcmp(InterpState &S, CodePtr OpPC,
   assert(A.getFieldDesc()->isPrimitiveArray());
   assert(B.getFieldDesc()->isPrimitiveArray());
 
+  bool StopAtZero =
+      (ID == Builtin::BIstrcmp || ID == Builtin::BI__builtin_strcmp ||
+       ID == Builtin::BIstrncmp || ID == Builtin::BI__builtin_strncmp);
+  bool IsRawByte = ID == Builtin::BImemcmp || ID == Builtin::BI__builtin_memcmp;
+
+  if (IsRawByte &&
+      (!isOneByteCharacterType(A.getFieldDesc()->getElemQualType()) ||
+       !isOneByteCharacterType(B.getFieldDesc()->getElemQualType()))) {
+    QualType CharTy1 = A.getFieldDesc()->getElemQualType();
+    QualType CharTy2 = B.getFieldDesc()->getElemQualType();
+    S.FFDiag(S.Current->getSource(OpPC),
+             diag::note_constexpr_memcmp_unsupported)
+        << ("'" + S.getASTContext().BuiltinInfo.getName(ID) + "'").str()
+        << CharTy1 << CharTy2;
+    return false;
+  }
+
   unsigned IndexA = A.getIndex();
   unsigned IndexB = B.getIndex();
   int32_t Result = 0;
@@ -243,7 +268,7 @@ static bool interp__builtin_strcmp(InterpState &S, CodePtr OpPC,
       Result = -1;
       break;
     }
-    if (CA == 0 || CB == 0)
+    if (StopAtZero && (CA == 0 || CB == 0))
       break;
   }
 
@@ -1904,6 +1929,8 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
   case Builtin::BIstrcmp:
   case Builtin::BI__builtin_strncmp:
   case Builtin::BIstrncmp:
+  case Builtin::BI__builtin_memcmp:
+  case Builtin::BImemcmp:
     if (!interp__builtin_strcmp(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 7dd08cb5fa1c35..485652867a44ec 100644
--- a/clang/test/AST/ByteCode/builtin-functions.cpp
+++ b/clang/test/AST/ByteCode/builtin-functions.cpp
@@ -1208,3 +1208,24 @@ namespace BuiltinMemcpy {
   static_assert(memcpyTypeRem() == 12); // both-error {{not an integral constant expression}} \
                                         // both-note {{in call to}}
 }
+
+namespace Memcmp {
+  constexpr unsigned char ku00fe00[] = {0x00, 0xfe, 0x00};
+  constexpr unsigned char ku00feff[] = {0x00, 0xfe, 0xff};
+  constexpr signed char ks00fe00[] = {0, -2, 0};
+  constexpr signed char ks00feff[] = {0, -2, -1};
+  static_assert(__builtin_memcmp(ku00feff, ks00fe00, 2) == 0);
+  static_assert(__builtin_memcmp(ku00feff, ks00fe00, 99) == 1);
+  static_assert(__builtin_memcmp(ku00fe00, ks00feff, 99) == -1);
+  static_assert(__builtin_memcmp(ks00feff, ku00fe00, 2) == 0);
+  static_assert(__builtin_memcmp(ks00feff, ku00fe00, 99) == 1);
+  static_assert(__builtin_memcmp(ks00fe00, ku00feff, 99) == -1);
+  static_assert(__builtin_memcmp(ks00fe00, ks00feff, 2) == 0);
+  static_assert(__builtin_memcmp(ks00feff, ks00fe00, 99) == 1);
+  static_assert(__builtin_memcmp(ks00fe00, ks00feff, 99) == -1);
+
+  struct Bool3Tuple { bool bb[3]; };
+  constexpr Bool3Tuple kb000100 = {{false, true, false}};
+  static_assert(sizeof(bool) != 1u || __builtin_memcmp(ks00fe00, kb000100.bb, 1) == 0); // both-error {{constant}} \
+                                                                                        // both-note {{not supported}}
+}

[aaronpuchert]

Check out https://lab.llvm.org/buildbot/#/builders/13/builds/4041:

RUN: at line 1: /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/stage1/bin/clang -cc1 -internal-isystem /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/stage1/lib/clang/20/include -nostdsysteminc -Wno-string-plus-int -fexperimental-new-constant-interpreter /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/clang/test/AST/ByteCode/builtin-functions.cpp -verify=expected,both
+ /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/stage1/bin/clang -cc1 -internal-isystem /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/stage1/lib/clang/20/include -nostdsysteminc -Wno-string-plus-int -fexperimental-new-constant-interpreter /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/clang/test/AST/ByteCode/builtin-functions.cpp -verify=expected,both
error: 'both-error' diagnostics seen but not expected: 
  File /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/clang/test/AST/ByteCode/builtin-functions.cpp Line 1232: static assertion failed due to requirement '__builtin_memcmp(ku00feff, ks00fe00, 2) == 0'
  File /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/clang/test/AST/ByteCode/builtin-functions.cpp Line 1235: static assertion failed due to requirement '__builtin_memcmp(ks00feff, ku00fe00, 2) == 0'
  File /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/clang/test/AST/ByteCode/builtin-functions.cpp Line 1238: static assertion failed due to requirement '__builtin_memcmp(ks00fe00, ks00feff, 2) == 0'
error: 'both-note' diagnostics seen but not expected: 
  File /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/clang/test/AST/ByteCode/builtin-functions.cpp Line 1232: expression evaluates to '1 == 0'
  File /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/clang/test/AST/ByteCode/builtin-functions.cpp Line 1235: expression evaluates to '1 == 0'
  File /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/clang/test/AST/ByteCode/builtin-functions.cpp Line 1238: expression evaluates to '-1 == 0'
8 errors generated.

[nikic]

We're seeing the same issue on s390x. Big endian not handled correctly?

[tbaederr]

Yup, see #119851