[clang][x86] Add constexpr support for ADC/SBB + ADX intrinsics (#110668)

ADC and ADX use the same internal intrinsics - for testing I've taken the same approach as the generic builtin overflow tests, putting the intrinsics in a constexpr test wrapper and comparing the carry/result value pair.

I've added the addcarry/subborrow intrinsics to the clang language extension list - I'm not sure if we want to add all ISA intrinsics to the list (although we can if people think it useful?), but I felt we should at least include the baseline x86 intrinsics.

1 files changed, 32 insertions, 0 deletions

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 48816d3..3a73cea 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -13464,6 +13464,38 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
     return Success(DidOverflow, E);
   }
 
+  case clang::X86::BI__builtin_ia32_addcarryx_u32:
+  case clang::X86::BI__builtin_ia32_addcarryx_u64:
+  case clang::X86::BI__builtin_ia32_subborrow_u32:
+  case clang::X86::BI__builtin_ia32_subborrow_u64: {
+    LValue ResultLValue;
+    APSInt CarryIn, LHS, RHS;
+    QualType ResultType = E->getArg(3)->getType()->getPointeeType();
+    if (!EvaluateInteger(E->getArg(0), CarryIn, Info) ||
+        !EvaluateInteger(E->getArg(1), LHS, Info) ||
+        !EvaluateInteger(E->getArg(2), RHS, Info) ||
+        !EvaluatePointer(E->getArg(3), ResultLValue, Info))
+      return false;
+
+    bool IsAdd = BuiltinOp == clang::X86::BI__builtin_ia32_addcarryx_u32 ||
+                 BuiltinOp == clang::X86::BI__builtin_ia32_addcarryx_u64;
+
+    unsigned BitWidth = LHS.getBitWidth();
+    unsigned CarryInBit = CarryIn.ugt(0) ? 1 : 0;
+    APInt ExResult =
+        IsAdd
+            ? (LHS.zext(BitWidth + 1) + (RHS.zext(BitWidth + 1) + CarryInBit))
+            : (LHS.zext(BitWidth + 1) - (RHS.zext(BitWidth + 1) + CarryInBit));
+
+    APInt Result = ExResult.extractBits(BitWidth, 0);
+    uint64_t CarryOut = ExResult.extractBitsAsZExtValue(1, BitWidth);
+
+    APValue APV{APSInt(Result, /*isUnsigned=*/true)};
+    if (!handleAssignment(Info, E, ResultLValue, ResultType, APV))
+      return false;
+    return Success(CarryOut, E);
+  }
+
   case clang::X86::BI__builtin_ia32_bextr_u32:
   case clang::X86::BI__builtin_ia32_bextr_u64:
   case clang::X86::BI__builtin_ia32_bextri_u32: