1 files changed, 71 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Analysis/OverflowInstAnalysis.cpp b/contrib/llvm-project/llvm/lib/Analysis/OverflowInstAnalysis.cpp
new file mode 100644
index 000000000000..8bfd6642f760
--- /dev/null
+++ b/contrib/llvm-project/llvm/lib/Analysis/OverflowInstAnalysis.cpp
@@ -0,0 +1,71 @@
+//==-- OverflowInstAnalysis.cpp - Utils to fold overflow insts ----*- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file holds routines to help analyse overflow instructions
+// and fold them into constants or other overflow instructions
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/OverflowInstAnalysis.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/PatternMatch.h"
+
+using namespace llvm;
+using namespace llvm::PatternMatch;
+
+bool llvm::isCheckForZeroAndMulWithOverflow(Value *Op0, Value *Op1, bool IsAnd,
+                                            Use *&Y) {
+  ICmpInst::Predicate Pred;
+  Value *X, *NotOp1;
+  int XIdx;
+  IntrinsicInst *II;
+
+  if (!match(Op0, m_ICmp(Pred, m_Value(X), m_Zero())))
+    return false;
+
+  ///   %Agg = call { i4, i1 } @llvm.[us]mul.with.overflow.i4(i4 %X, i4 %???)
+  ///   %V = extractvalue { i4, i1 } %Agg, 1
+  auto matchMulOverflowCheck = [X, &II, &XIdx](Value *V) {
+    auto *Extract = dyn_cast<ExtractValueInst>(V);
+    // We should only be extracting the overflow bit.
+    if (!Extract || !Extract->getIndices().equals(1))
+      return false;
+
+    II = dyn_cast<IntrinsicInst>(Extract->getAggregateOperand());
+    if (!II ||
+        !match(II, m_CombineOr(m_Intrinsic<Intrinsic::umul_with_overflow>(),
+                               m_Intrinsic<Intrinsic::smul_with_overflow>())))
+      return false;
+
+    if (II->getArgOperand(0) == X)
+      XIdx = 0;
+    else if (II->getArgOperand(1) == X)
+      XIdx = 1;
+    else
+      return false;
+    return true;
+  };
+
+  bool Matched =
+      (IsAnd && Pred == ICmpInst::Predicate::ICMP_NE &&
+       matchMulOverflowCheck(Op1)) ||
+      (!IsAnd && Pred == ICmpInst::Predicate::ICMP_EQ &&
+       match(Op1, m_Not(m_Value(NotOp1))) && matchMulOverflowCheck(NotOp1));
+
+  if (!Matched)
+    return false;
+
+  Y = &II->getArgOperandUse(!XIdx);
+  return true;
+}
+
+bool llvm::isCheckForZeroAndMulWithOverflow(Value *Op0, Value *Op1,
+                                            bool IsAnd) {
+  Use *Y;
+  return isCheckForZeroAndMulWithOverflow(Op0, Op1, IsAnd, Y);
+}