[ADT][APInt] add sfloordiv_ov APInt's member function

[lipracer]

for mlir fold to avoid too many overflow state check

[llvmbot]

@llvm/pr-subscribers-llvm-adt

@llvm/pr-subscribers-llvm-support

Author: long.chen (lipracer)

Changes

for mlir fold to avoid too many overflow state check

---

Full diff: https://github.com/llvm/llvm-project/pull/84720.diff

3 Files Affected:

• (modified) llvm/include/llvm/ADT/APInt.h (+1)
• (modified) llvm/lib/Support/APInt.cpp (+8)
• (modified) llvm/unittests/ADT/APIntTest.cpp (+38)

diff --git a/llvm/include/llvm/ADT/APInt.h b/llvm/include/llvm/ADT/APInt.h
index 1fc3c7b2236a17..8a085f8b05ebbd 100644
--- a/llvm/include/llvm/ADT/APInt.h
+++ b/llvm/include/llvm/ADT/APInt.h
@@ -996,6 +996,7 @@ class [[nodiscard]] APInt {
   APInt sshl_ov(unsigned Amt, bool &Overflow) const;
   APInt ushl_ov(const APInt &Amt, bool &Overflow) const;
   APInt ushl_ov(unsigned Amt, bool &Overflow) const;
+  APInt sfloordiv_ov(const APInt &RHS, bool &Overflow) const;
 
   // Operations that saturate
   APInt sadd_sat(const APInt &RHS) const;
diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index e686b976523302..3bff2856cbdc54 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -2022,6 +2022,14 @@ APInt APInt::ushl_ov(unsigned ShAmt, bool &Overflow) const {
   return *this << ShAmt;
 }
 
+APInt APInt::sfloordiv_ov(const APInt &RHS, bool &Overflow) const {
+  auto quotient = sdiv_ov(RHS, Overflow);
+  if ((quotient * RHS != *this) && (isNegative() != RHS.isNegative()))
+    return quotient - 1;
+  else
+    return quotient;
+}
+
 APInt APInt::sadd_sat(const APInt &RHS) const {
   bool Overflow;
   APInt Res = sadd_ov(RHS, Overflow);
diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index 24324822356bf6..5485978934ed07 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -14,6 +14,7 @@
 #include "llvm/Support/Alignment.h"
 #include "gtest/gtest.h"
 #include <array>
+#include <limits>
 #include <optional>
 
 using namespace llvm;
@@ -2928,6 +2929,43 @@ TEST(APIntTest, smul_ov) {
       }
 }
 
+TEST(APIntTest, sfloordiv_ov) {
+  // test negative quotient
+  {
+    APInt divisor(32, -3, true);
+    APInt dividend(32, 2, true);
+    bool Overflow = false;
+    auto quotient = divisor.sfloordiv_ov(dividend, Overflow);
+    EXPECT_FALSE(Overflow);
+    EXPECT_EQ(-2, quotient.getSExtValue());
+  }
+  // test positive quotient
+  {
+    APInt divisor(32, 3, true);
+    APInt dividend(32, 2, true);
+    bool Overflow = false;
+    auto quotient = divisor.sfloordiv_ov(dividend, Overflow);
+    EXPECT_FALSE(Overflow);
+    EXPECT_EQ(1, quotient.getSExtValue());
+  }
+  // test overflow
+  {
+    auto check_overflow_one = [](auto arg) {
+      using IntTy = decltype(arg);
+      APInt divisor(8 * sizeof(arg), std::numeric_limits<IntTy>::lowest(),
+                    true);
+      APInt dividend(8 * sizeof(arg), IntTy(-1), true);
+      bool Overflow = false;
+      [[maybe_unused]] auto quotient = divisor.sfloordiv_ov(dividend, Overflow);
+      EXPECT_TRUE(Overflow);
+    };
+    auto check_overflow_all = [&](auto... args) {
+      (void)std::initializer_list<int>{(check_overflow_one(args), 0)...};
+    };
+    std::apply(check_overflow_all, std::tuple<char, short, int, int64_t>());
+  }
+}
+
 TEST(APIntTest, SolveQuadraticEquationWrap) {
   // Verify that "Solution" is the first non-negative integer that solves
   // Ax^2 + Bx + C = "0 or overflow", i.e. that it is a correct solution

[kuhar]

Could we exhaustively test this on int8 against some reference implementation? Maybe something in numpy, etc., just to be confident that this implementation is correct.