Implement constexpr __builtin_*_overflow
As requested here:https://bugs.llvm.org/show_bug.cgi?id=37633
permit the __builtin_*_overflow builtins in constexpr functions.
Differential Revision: https://reviews.llvm.org/D48040
llvm-svn: 334650
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 590ebba..028834e 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -8155,6 +8155,124 @@
case Builtin::BIomp_is_initial_device:
// We can decide statically which value the runtime would return if called.
return Success(Info.getLangOpts().OpenMPIsDevice ? 0 : 1, E);
+ case Builtin::BI__builtin_add_overflow:
+ case Builtin::BI__builtin_sub_overflow:
+ case Builtin::BI__builtin_mul_overflow:
+ case Builtin::BI__builtin_sadd_overflow:
+ case Builtin::BI__builtin_uadd_overflow:
+ case Builtin::BI__builtin_uaddl_overflow:
+ case Builtin::BI__builtin_uaddll_overflow:
+ case Builtin::BI__builtin_usub_overflow:
+ case Builtin::BI__builtin_usubl_overflow:
+ case Builtin::BI__builtin_usubll_overflow:
+ case Builtin::BI__builtin_umul_overflow:
+ case Builtin::BI__builtin_umull_overflow:
+ case Builtin::BI__builtin_umulll_overflow:
+ case Builtin::BI__builtin_saddl_overflow:
+ case Builtin::BI__builtin_saddll_overflow:
+ case Builtin::BI__builtin_ssub_overflow:
+ case Builtin::BI__builtin_ssubl_overflow:
+ case Builtin::BI__builtin_ssubll_overflow:
+ case Builtin::BI__builtin_smul_overflow:
+ case Builtin::BI__builtin_smull_overflow:
+ case Builtin::BI__builtin_smulll_overflow: {
+ LValue ResultLValue;
+ APSInt LHS, RHS;
+
+ QualType ResultType = E->getArg(2)->getType()->getPointeeType();
+ if (!EvaluateInteger(E->getArg(0), LHS, Info) ||
+ !EvaluateInteger(E->getArg(1), RHS, Info) ||
+ !EvaluatePointer(E->getArg(2), ResultLValue, Info))
+ return false;
+
+ APSInt Result;
+ bool DidOverflow = false;
+
+ // If the types don't have to match, enlarge all 3 to the largest of them.
+ if (BuiltinOp == Builtin::BI__builtin_add_overflow ||
+ BuiltinOp == Builtin::BI__builtin_sub_overflow ||
+ BuiltinOp == Builtin::BI__builtin_mul_overflow) {
+ bool IsSigned = LHS.isSigned() || RHS.isSigned() ||
+ ResultType->isSignedIntegerOrEnumerationType();
+ bool AllSigned = LHS.isSigned() && RHS.isSigned() &&
+ ResultType->isSignedIntegerOrEnumerationType();
+ uint64_t LHSSize = LHS.getBitWidth();
+ uint64_t RHSSize = RHS.getBitWidth();
+ uint64_t ResultSize = Info.Ctx.getTypeSize(ResultType);
+ uint64_t MaxBits = std::max(std::max(LHSSize, RHSSize), ResultSize);
+
+ // Add an additional bit if the signedness isn't uniformly agreed to. We
+ // could do this ONLY if there is a signed and an unsigned that both have
+ // MaxBits, but the code to check that is pretty nasty. The issue will be
+ // caught in the shrink-to-result later anyway.
+ if (IsSigned && !AllSigned)
+ ++MaxBits;
+
+ LHS = APSInt(IsSigned ? LHS.sextOrSelf(MaxBits) : LHS.zextOrSelf(MaxBits),
+ !IsSigned);
+ RHS = APSInt(IsSigned ? RHS.sextOrSelf(MaxBits) : RHS.zextOrSelf(MaxBits),
+ !IsSigned);
+ Result = APSInt(MaxBits, !IsSigned);
+ }
+
+ // Find largest int.
+ switch (BuiltinOp) {
+ default:
+ llvm_unreachable("Invalid value for BuiltinOp");
+ case Builtin::BI__builtin_add_overflow:
+ case Builtin::BI__builtin_sadd_overflow:
+ case Builtin::BI__builtin_saddl_overflow:
+ case Builtin::BI__builtin_saddll_overflow:
+ case Builtin::BI__builtin_uadd_overflow:
+ case Builtin::BI__builtin_uaddl_overflow:
+ case Builtin::BI__builtin_uaddll_overflow:
+ Result = LHS.isSigned() ? LHS.sadd_ov(RHS, DidOverflow)
+ : LHS.uadd_ov(RHS, DidOverflow);
+ break;
+ case Builtin::BI__builtin_sub_overflow:
+ case Builtin::BI__builtin_ssub_overflow:
+ case Builtin::BI__builtin_ssubl_overflow:
+ case Builtin::BI__builtin_ssubll_overflow:
+ case Builtin::BI__builtin_usub_overflow:
+ case Builtin::BI__builtin_usubl_overflow:
+ case Builtin::BI__builtin_usubll_overflow:
+ Result = LHS.isSigned() ? LHS.ssub_ov(RHS, DidOverflow)
+ : LHS.usub_ov(RHS, DidOverflow);
+ break;
+ case Builtin::BI__builtin_mul_overflow:
+ case Builtin::BI__builtin_smul_overflow:
+ case Builtin::BI__builtin_smull_overflow:
+ case Builtin::BI__builtin_smulll_overflow:
+ case Builtin::BI__builtin_umul_overflow:
+ case Builtin::BI__builtin_umull_overflow:
+ case Builtin::BI__builtin_umulll_overflow:
+ Result = LHS.isSigned() ? LHS.smul_ov(RHS, DidOverflow)
+ : LHS.umul_ov(RHS, DidOverflow);
+ break;
+ }
+
+ // In the case where multiple sizes are allowed, truncate and see if
+ // the values are the same.
+ if (BuiltinOp == Builtin::BI__builtin_add_overflow ||
+ BuiltinOp == Builtin::BI__builtin_sub_overflow ||
+ BuiltinOp == Builtin::BI__builtin_mul_overflow) {
+ // APSInt doesn't have a TruncOrSelf, so we use extOrTrunc instead,
+ // since it will give us the behavior of a TruncOrSelf in the case where
+ // its parameter <= its size. We previously set Result to be at least the
+ // type-size of the result, so getTypeSize(ResultType) <= Result.BitWidth
+ // will work exactly like TruncOrSelf.
+ APSInt Temp = Result.extOrTrunc(Info.Ctx.getTypeSize(ResultType));
+ Temp.setIsSigned(ResultType->isSignedIntegerOrEnumerationType());
+
+ if (!APSInt::isSameValue(Temp, Result))
+ DidOverflow = true;
+ Result = Temp;
+ }
+
+ APValue APV{Result};
+ handleAssignment(Info, E, ResultLValue, ResultType, APV);
+ return Success(DidOverflow, E);
+ }
}
}