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[ADT] Add fshl/fshr operations to APInt #153790

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Merged
RKSimon merged 2 commits into from
Aug 21, 2025
Merged

[ADT] Add fshl/fshr operations to APInt #153790

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7b72eb2
[ADT] Add fshl/fshr operations to APInt
ckoparkar Aug 15, 2025
efa0fe0
Remove outer APInt constructor
ckoparkar Aug 21, 2025
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29 changes: 29 additions & 0 deletions llvm/include/llvm/ADT/APInt.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2410,6 +2410,35 @@ LLVM_ABI std::optional<unsigned> GetMostSignificantDifferentBit(const APInt &A,
/// A.getBitwidth() or NewBitWidth must be a whole multiples of the other.
LLVM_ABI APInt ScaleBitMask(const APInt &A, unsigned NewBitWidth,
bool MatchAllBits = false);

/// Perform a funnel shift left.
///
/// Concatenate Hi and Lo (Hi is the most significant bits of the wide value),
/// the combined value is shifted left by Shift (modulo the bit width of the
/// original arguments), and the most significant bits are extracted to produce
/// a result that is the same size as the original arguments.
///
/// Examples:
/// (1) fshl(i8 255, i8 0, i8 15) = 128 (0b10000000)
/// (2) fshl(i8 15, i8 15, i8 11) = 120 (0b01111000)
/// (3) fshl(i8 0, i8 255, i8 8) = 0 (0b00000000)
/// (4) fshl(i8 255, i8 0, i8 15) = fshl(i8 255, i8 0, i8 7) // 15 % 8
LLVM_ABI APInt fshl(const APInt &Hi, const APInt &Lo, const APInt &Shift);

/// Perform a funnel shift right.
///
/// Concatenate Hi and Lo (Hi is the most significant bits of the wide value),
/// the combined value is shifted right by Shift (modulo the bit width of the
/// original arguments), and the least significant bits are extracted to produce
/// a result that is the same size as the original arguments.
///
/// Examples:
/// (1) fshr(i8 255, i8 0, i8 15) = 254 (0b11111110)
/// (2) fshr(i8 15, i8 15, i8 11) = 225 (0b11100001)
/// (3) fshr(i8 0, i8 255, i8 8) = 255 (0b11111111)
/// (4) fshr(i8 255, i8 0, i8 9) = fshr(i8 255, i8 0, i8 1) // 9 % 8
LLVM_ABI APInt fshr(const APInt &Hi, const APInt &Lo, const APInt &Shift);

} // namespace APIntOps

// See friend declaration above. This additional declaration is required in
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18 changes: 18 additions & 0 deletions llvm/lib/Support/APInt.cpp
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Expand Up @@ -3169,3 +3169,21 @@ APInt APIntOps::pow(const APInt &X, int64_t N) {
}
return Acc;
}

APInt llvm::APIntOps::fshl(const APInt &Hi, const APInt &Lo,
const APInt &Shift) {
assert(Hi.getBitWidth() == Lo.getBitWidth());
unsigned ShiftAmt = rotateModulo(Hi.getBitWidth(), Shift);
if (ShiftAmt == 0)
return Hi;
return APInt(Hi.shl(ShiftAmt) | Lo.lshr(Hi.getBitWidth() - ShiftAmt));
}

APInt llvm::APIntOps::fshr(const APInt &Hi, const APInt &Lo,
const APInt &Shift) {
assert(Hi.getBitWidth() == Lo.getBitWidth());
unsigned ShiftAmt = rotateModulo(Hi.getBitWidth(), Shift);
if (ShiftAmt == 0)
return Lo;
return APInt(Hi.shl(Hi.getBitWidth() - ShiftAmt) | Lo.lshr(ShiftAmt));
}
76 changes: 76 additions & 0 deletions llvm/unittests/ADT/APIntTest.cpp
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Expand Up @@ -3744,4 +3744,80 @@ TEST(APIntTest, TryExt) {
ASSERT_EQ(42, APInt(128, -1).trySExtValue().value_or(42));
}

TEST(APIntTest, Fshl) {
EXPECT_EQ(
APIntOps::fshl(APInt(8, 0), APInt(8, 255), APInt(8, 8)).getZExtValue(),
0);
EXPECT_EQ(
APIntOps::fshl(APInt(8, 255), APInt(8, 0), APInt(8, 8)).getZExtValue(),
255);
EXPECT_EQ(
APIntOps::fshl(APInt(8, 255), APInt(8, 0), APInt(8, 15)).getZExtValue(),
128);
EXPECT_EQ(
APIntOps::fshl(APInt(8, 15), APInt(8, 15), APInt(8, 11)).getZExtValue(),
120);
EXPECT_EQ(
APIntOps::fshl(APInt(8, 2), APInt(8, 1), APInt(8, 3)).getZExtValue(), 16);
EXPECT_EQ(
APIntOps::fshl(APInt(8, 2), APInt(8, 1), APInt(8, 1)).getZExtValue(),
APIntOps::fshl(APInt(8, 2), APInt(8, 1), APInt(8, 9)).getZExtValue());
EXPECT_EQ(
APIntOps::fshl(APInt(8, 2), APInt(8, 1), APInt(8, 7)).getZExtValue(),
APIntOps::fshl(APInt(8, 2), APInt(8, 1), APInt(8, 15)).getZExtValue());
EXPECT_EQ(APIntOps::fshl(APInt(32, 0, /*isSigned*/ true),
APInt(32, 2147483647, /*isSigned*/ true),
APInt(32, 32, /*isSigned*/ true))
.getSExtValue(),
0);
EXPECT_EQ(APIntOps::fshl(APInt(64, 1, /*isSigned*/ true),
APInt(64, 2, /*isSigned*/ true),
APInt(64, 3, /*isSigned*/ true))
.getSExtValue(),
8);
EXPECT_EQ(APIntOps::fshl(APInt(16, -2, /*isSigned*/ true),
APInt(16, -1, /*isSigned*/ true),
APInt(16, 3, /*isSigned*/ true))
.getSExtValue(),
-9);
}

TEST(APIntTest, Fshr) {
EXPECT_EQ(
APIntOps::fshr(APInt(8, 0), APInt(8, 255), APInt(8, 8)).getZExtValue(),
255);
EXPECT_EQ(
APIntOps::fshr(APInt(8, 255), APInt(8, 0), APInt(8, 8)).getZExtValue(),
0);
EXPECT_EQ(
APIntOps::fshr(APInt(8, 255), APInt(8, 0), APInt(8, 15)).getZExtValue(),
254);
EXPECT_EQ(
APIntOps::fshr(APInt(8, 15), APInt(8, 15), APInt(8, 11)).getZExtValue(),
225);
EXPECT_EQ(
APIntOps::fshr(APInt(8, 1), APInt(8, 2), APInt(8, 3)).getZExtValue(), 32);
EXPECT_EQ(
APIntOps::fshr(APInt(8, 1), APInt(8, 2), APInt(8, 1)).getZExtValue(),
APIntOps::fshr(APInt(8, 1), APInt(8, 2), APInt(8, 9)).getZExtValue());
EXPECT_EQ(
APIntOps::fshr(APInt(8, 1), APInt(8, 2), APInt(8, 7)).getZExtValue(),
APIntOps::fshr(APInt(8, 1), APInt(8, 2), APInt(8, 15)).getZExtValue());
EXPECT_EQ(APIntOps::fshr(APInt(64, 0, /*isSigned*/ true),
APInt(64, 9223372036854775807, /*isSigned*/ true),
APInt(64, 64, /*isSigned*/ true))
.getSExtValue(),
9223372036854775807);
EXPECT_EQ(APIntOps::fshr(APInt(64, 1, /*isSigned*/ true),
APInt(64, 2, /*isSigned*/ true),
APInt(64, 3, /*isSigned*/ true))
.getSExtValue(),
2305843009213693952);
EXPECT_EQ(APIntOps::fshr(APInt(16, -2, /*isSigned*/ true),
APInt(16, -1, /*isSigned*/ true),
APInt(16, 3, /*isSigned*/ true))
.getSExtValue(),
-8193);
}

} // end anonymous namespace