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

[via cfe-commits]

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@@ -13464,6 +13464,54 @@ 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: {
+    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;
+
+    unsigned BitWidth = LHS.getBitWidth();
+    APInt ExResult = LHS.zext(BitWidth + 1) + RHS.zext(BitWidth + 1) +
+                     (CarryIn.ugt(0) ? 1 : 0);
+
+    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_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;
+
+    unsigned BitWidth = LHS.getBitWidth();
+    APInt ExResult = LHS.zext(BitWidth + 1) -
+                     (RHS.zext(BitWidth + 1) + (CarryIn.ugt(0) ? 1 : 0));
+
+    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);
+  }
----------------
goldsteinn wrote:

Seems like a lot of dup code between these two cases. How about just using a bool to decide on add/sub between `LHS` and `RHS + Carry`?

https://github.com/llvm/llvm-project/pull/110668