[InstCombine] Fold add nsw + sadd.with.overflow
Fold `add nsw` and `sadd.with.overflow` with constants if the addition
does not overflow.
Part of https://bugs.llvm.org/show_bug.cgi?id=38146.
Patch by Dan Robertson.
Differential Revision: https://reviews.llvm.org/D58881
llvm-svn: 355530
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 56d5c89..02cf906 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1814,6 +1814,19 @@
return nullptr;
}
+Instruction *InstCombiner::foldIntrinsicWithOverflowCommon(IntrinsicInst *II) {
+ OverflowCheckFlavor OCF =
+ IntrinsicIDToOverflowCheckFlavor(II->getIntrinsicID());
+ assert(OCF != OCF_INVALID && "unexpected!");
+
+ Value *OperationResult = nullptr;
+ Constant *OverflowResult = nullptr;
+ if (OptimizeOverflowCheck(OCF, II->getArgOperand(0), II->getArgOperand(1),
+ *II, OperationResult, OverflowResult))
+ return CreateOverflowTuple(II, OperationResult, OverflowResult);
+ return nullptr;
+}
+
/// CallInst simplification. This mostly only handles folding of intrinsic
/// instructions. For normal calls, it allows visitCallBase to do the heavy
/// lifting.
@@ -2016,8 +2029,32 @@
return &CI;
break;
}
+ case Intrinsic::sadd_with_overflow: {
+ if (Instruction *I = canonicalizeConstantArg0ToArg1(CI))
+ return I;
+ if (Instruction *I = foldIntrinsicWithOverflowCommon(II))
+ return I;
+
+ // Given 2 constant operands whose sum does not overflow:
+ // saddo (X +nsw C0), C1 -> saddo X, C0 + C1
+ Value *X;
+ const APInt *C0, *C1;
+ Value *Arg0 = II->getArgOperand(0);
+ Value *Arg1 = II->getArgOperand(1);
+ if (match(Arg0, m_NSWAdd(m_Value(X), m_APInt(C0))) &&
+ match(Arg1, m_APInt(C1))) {
+ bool Overflow;
+ APInt NewC = C1->sadd_ov(*C0, Overflow);
+ if (!Overflow)
+ return replaceInstUsesWith(
+ *II, Builder.CreateBinaryIntrinsic(
+ Intrinsic::sadd_with_overflow, X,
+ ConstantInt::get(Arg1->getType(), NewC)));
+ }
+
+ break;
+ }
case Intrinsic::uadd_with_overflow:
- case Intrinsic::sadd_with_overflow:
case Intrinsic::umul_with_overflow:
case Intrinsic::smul_with_overflow:
if (Instruction *I = canonicalizeConstantArg0ToArg1(CI))
@@ -2026,15 +2063,8 @@
case Intrinsic::usub_with_overflow:
case Intrinsic::ssub_with_overflow: {
- OverflowCheckFlavor OCF =
- IntrinsicIDToOverflowCheckFlavor(II->getIntrinsicID());
- assert(OCF != OCF_INVALID && "unexpected!");
-
- Value *OperationResult = nullptr;
- Constant *OverflowResult = nullptr;
- if (OptimizeOverflowCheck(OCF, II->getArgOperand(0), II->getArgOperand(1),
- *II, OperationResult, OverflowResult))
- return CreateOverflowTuple(II, OperationResult, OverflowResult);
+ if (Instruction *I = foldIntrinsicWithOverflowCommon(II))
+ return I;
break;
}