Revert "Respect integer overflow handling in abs builtin"

This reverts commit 1783185,
which broke the buildbots, starting with when it was first built in https://lab.llvm.org/buildbot/#/builders/85/builds/18390

(N.B. I think the patch is uncovering real bugs; the revert
is simply to keep the tree green and the buildbots useful, because I'm not confident how to
fix-forward all the found bugs.)

Author: thurstond

clang/docs/ReleaseNotes.rst

@@ -154,10 +154,6 @@ Bug Fixes in This Version
 - Fix a hang on valid C code passing a function type as an argument to
   ``typeof`` to form a function declaration.
   (`#64713 <https://github.com/llvm/llvm-project/issues/64713>_`)
-- Clang now respects ``-fwrapv`` and ``-ftrapv`` for ``__builtin_abs`` and
-  ``abs`` builtins.
-  (`#45129 <https://github.com/llvm/llvm-project/issues/45129>`_,
-  `#45794 <https://github.com/llvm/llvm-project/issues/45794>`_)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -293,9 +289,6 @@ Static Analyzer
 
 Sanitizers
 ----------
-- ``-fsanitize=signed-integer-overflow`` now instruments ``__builtin_abs`` and
-  ``abs`` builtins.
-
 
 Python Binding Changes
 ----------------------

clang/lib/CodeGen/CGBuiltin.cpp

@@ -1768,49 +1768,6 @@ Value *CodeGenFunction::EmitCheckedArgForBuiltin(const Expr *E,
   return ArgValue;
 }
 
-static Value *EmitAbs(CodeGenFunction &CGF, Value *ArgValue, bool HasNSW) {
-  // X < 0 ? -X : X
-  // TODO: Use phi-node (for better SimplifyCFGPass)
-  Value *NegOp = CGF.Builder.CreateNeg(ArgValue, "neg", false, HasNSW);
-  Constant *Zero = llvm::Constant::getNullValue(ArgValue->getType());
-  Value *CmpResult = CGF.Builder.CreateICmpSLT(ArgValue, Zero, "abscond");
-  return CGF.Builder.CreateSelect(CmpResult, NegOp, ArgValue, "abs");
-}
-
-static Value *EmitOverflowCheckedAbs(CodeGenFunction &CGF, const CallExpr *E,
-                                     bool SanitizeOverflow) {
-  Value *ArgValue = CGF.EmitScalarExpr(E->getArg(0));
-
-  // Try to eliminate overflow check.
-  if (const auto *VCI = dyn_cast<llvm::ConstantInt>(ArgValue)) {
-    if (!VCI->isMinSignedValue()) {
-      return EmitAbs(CGF, ArgValue, true);
-    }
-  }
-
-  CodeGenFunction::SanitizerScope SanScope(&CGF);
-
-  Constant *Zero = Constant::getNullValue(ArgValue->getType());
-  Value *ResultAndOverflow = CGF.Builder.CreateBinaryIntrinsic(
-      Intrinsic::ssub_with_overflow, Zero, ArgValue);
-  Value *Result = CGF.Builder.CreateExtractValue(ResultAndOverflow, 0);
-  Value *NotOverflow = CGF.Builder.CreateNot(
-      CGF.Builder.CreateExtractValue(ResultAndOverflow, 1));
-
-  // TODO: support -ftrapv-handler.
-  if (SanitizeOverflow) {
-    CGF.EmitCheck({{NotOverflow, SanitizerKind::SignedIntegerOverflow}},
-                  SanitizerHandler::NegateOverflow,
-                  {CGF.EmitCheckSourceLocation(E->getArg(0)->getExprLoc()),
-                   CGF.EmitCheckTypeDescriptor(E->getType())},
-                  {ArgValue});
-  } else
-    CGF.EmitTrapCheck(NotOverflow, SanitizerHandler::SubOverflow);
-
-  Value *CmpResult = CGF.Builder.CreateICmpSLT(ArgValue, Zero, "abscond");
-  return CGF.Builder.CreateSelect(CmpResult, Result, ArgValue, "abs");
-}
-
 /// Get the argument type for arguments to os_log_helper.
 static CanQualType getOSLogArgType(ASTContext &C, int Size) {
   QualType UnsignedTy = C.getIntTypeForBitwidth(Size * 8, /*Signed=*/false);
@@ -2669,29 +2626,16 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     Builder.CreateCall(CGM.getIntrinsic(Intrinsic::vacopy), {DstPtr, SrcPtr});
     return RValue::get(nullptr);
   }
-  case Builtin::BIabs:
-  case Builtin::BIlabs:
-  case Builtin::BIllabs:
   case Builtin::BI__builtin_abs:
   case Builtin::BI__builtin_labs:
   case Builtin::BI__builtin_llabs: {
-    bool SanitizeOverflow = SanOpts.has(SanitizerKind::SignedIntegerOverflow);
-
-    Value *Result;
-    switch (getLangOpts().getSignedOverflowBehavior()) {
-    case LangOptions::SOB_Defined:
-      Result = EmitAbs(*this, EmitScalarExpr(E->getArg(0)), false);
-      break;
-    case LangOptions::SOB_Undefined:
-      if (!SanitizeOverflow) {
-        Result = EmitAbs(*this, EmitScalarExpr(E->getArg(0)), true);
-        break;
-      }
-      [[fallthrough]];
-    case LangOptions::SOB_Trapping:
-      Result = EmitOverflowCheckedAbs(*this, E, SanitizeOverflow);
-      break;
-    }
+    // X < 0 ? -X : X
+    // The negation has 'nsw' because abs of INT_MIN is undefined.
+    Value *ArgValue = EmitScalarExpr(E->getArg(0));
+    Value *NegOp = Builder.CreateNSWNeg(ArgValue, "neg");
+    Constant *Zero = llvm::Constant::getNullValue(ArgValue->getType());
+    Value *CmpResult = Builder.CreateICmpSLT(ArgValue, Zero, "abscond");
+    Value *Result = Builder.CreateSelect(CmpResult, NegOp, ArgValue, "abs");
     return RValue::get(Result);
   }
   case Builtin::BI__builtin_complex: {