[llvm] [ADT] Add fshl/fshr operations to APSInt (PR #153790)
Chaitanya Koparkar via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 15 05:07:09 PDT 2025
https://github.com/ckoparkar updated https://github.com/llvm/llvm-project/pull/153790
>From 927f385e116bd20b1c2f4a703561d6abee361f2e Mon Sep 17 00:00:00 2001
From: Chaitanya Koparkar <ckoparkar at gmail.com>
Date: Fri, 15 Aug 2025 07:24:12 -0400
Subject: [PATCH] [ADT] Add fshl/fshr operations to APSInt
---
llvm/include/llvm/ADT/APSInt.h | 20 ++++++
llvm/lib/Support/APSInt.cpp | 22 ++++++
llvm/unittests/ADT/APSIntTest.cpp | 113 ++++++++++++++++++++++++++++++
3 files changed, 155 insertions(+)
diff --git a/llvm/include/llvm/ADT/APSInt.h b/llvm/include/llvm/ADT/APSInt.h
index 88a7a6e71c817..74d4daadcc8f1 100644
--- a/llvm/include/llvm/ADT/APSInt.h
+++ b/llvm/include/llvm/ADT/APSInt.h
@@ -152,6 +152,9 @@ class [[nodiscard]] APSInt : public APInt {
APSInt operator>>(unsigned Amt) const {
return IsUnsigned ? APSInt(lshr(Amt), true) : APSInt(ashr(Amt), false);
}
+ APSInt operator>>(const APSInt &Amt) const {
+ return IsUnsigned ? APSInt(lshr(Amt), true) : APSInt(ashr(Amt), false);
+ }
APSInt &operator>>=(unsigned Amt) {
if (IsUnsigned)
lshrInPlace(Amt);
@@ -211,6 +214,9 @@ class [[nodiscard]] APSInt : public APInt {
APSInt operator<<(unsigned Bits) const {
return APSInt(static_cast<const APInt &>(*this) << Bits, IsUnsigned);
}
+ APSInt operator<<(const APSInt &Amt) const {
+ return APSInt(static_cast<const APInt &>(*this) << Amt, IsUnsigned);
+ }
APSInt &operator<<=(unsigned Amt) {
static_cast<APInt &>(*this) <<= Amt;
return *this;
@@ -387,6 +393,20 @@ template <> struct DenseMapInfo<APSInt, void> {
}
};
+namespace APSIntOps {
+
+/// Perform a funnel shift left.
+///
+/// fshl(X,Y,Z): (X << (Z % BW)) | (Y >> (BW - (Z % BW)))
+LLVM_ABI APSInt fshl(const APSInt &Hi, const APSInt &Lo, const APSInt &Shift);
+
+/// Perform a funnel shift right.
+///
+/// fshr(X,Y,Z): (X << (BW - (Z % BW))) | (Y >> (Z % BW))
+LLVM_ABI APSInt fshr(const APSInt &Hi, const APSInt &Lo, const APSInt &Shift);
+
+} // namespace APSIntOps
+
} // end namespace llvm
#endif
diff --git a/llvm/lib/Support/APSInt.cpp b/llvm/lib/Support/APSInt.cpp
index 5a9f44f304a27..09cbb2e6dc538 100644
--- a/llvm/lib/Support/APSInt.cpp
+++ b/llvm/lib/Support/APSInt.cpp
@@ -41,3 +41,25 @@ void APSInt::Profile(FoldingSetNodeID& ID) const {
ID.AddInteger((unsigned) (IsUnsigned ? 1 : 0));
APInt::Profile(ID);
}
+
+APSInt llvm::APSIntOps::fshl(const APSInt &Hi, const APSInt &Lo,
+ const APSInt &Shift) {
+ bool IsUnsigned = Hi.isUnsigned();
+ APSInt BitWidth(
+ APInt(Hi.getBitWidth(), static_cast<uint64_t>(Hi.getBitWidth())),
+ IsUnsigned);
+ return APSInt((Hi << (Shift % BitWidth)) |
+ (Lo >> (BitWidth - (Shift % BitWidth))),
+ IsUnsigned);
+}
+
+APSInt llvm::APSIntOps::fshr(const APSInt &Hi, const APSInt &Lo,
+ const APSInt &Shift) {
+ bool IsUnsigned = Hi.isUnsigned();
+ APSInt BitWidth(
+ APInt(Hi.getBitWidth(), static_cast<uint64_t>(Hi.getBitWidth())),
+ IsUnsigned);
+ return APSInt((Hi << (BitWidth - (Shift % BitWidth))) |
+ (Lo >> (Shift % BitWidth)),
+ IsUnsigned);
+}
diff --git a/llvm/unittests/ADT/APSIntTest.cpp b/llvm/unittests/ADT/APSIntTest.cpp
index 2d2a64433da94..658493f49d110 100644
--- a/llvm/unittests/ADT/APSIntTest.cpp
+++ b/llvm/unittests/ADT/APSIntTest.cpp
@@ -285,4 +285,117 @@ TEST(APSIntTest, UnsignedHighBit) {
EXPECT_TRUE(CharMax.isStrictlyPositive());
}
+// Right shift of unsigned numbers translates to a logical shift.
+TEST(APSIntTest, RightShiftUnsigned) {
+ // Right shift of a negative number.
+ const APInt neg_one(128, static_cast<uint64_t>(-1), /*isSigned*/ true);
+ const APSInt neg_one_unsigned(APSInt(neg_one, /*isUnsigned*/ true));
+ EXPECT_EQ(neg_one_unsigned >> 128, 0);
+
+ APSInt i256(APSInt(APInt::getHighBitsSet(256, 2)));
+ i256 >>= 1;
+ EXPECT_EQ(i256.countl_zero(), 1U);
+ EXPECT_EQ(i256.countr_zero(), 253U);
+ EXPECT_EQ(i256.popcount(), 2U);
+
+ i256 >>= 62;
+ EXPECT_EQ(i256.countl_zero(), 63U);
+ EXPECT_EQ(i256.countr_zero(), 191U);
+ EXPECT_EQ(i256.popcount(), 2U);
+}
+
+// Right shift of signed numbers translates to a arithmetic shift.
+TEST(APSIntTest, RightShiftSigned) {
+ // Right shift of a negative number.
+ const APInt neg_one = APInt(64, static_cast<uint64_t>(-1), /*isSigned*/ true);
+ const APSInt neg_one_signed(APSInt(neg_one, /*isUnsigned*/ false));
+ EXPECT_EQ(neg_one_signed >> 7, neg_one);
+
+ APSInt i72(APSInt(APInt::getHighBitsSet(72, 1), /*isUnsigned*/ false));
+ i72 >>= 46;
+ EXPECT_EQ(i72.countl_one(), 47U);
+ EXPECT_EQ(i72.countr_zero(), 25U);
+ EXPECT_EQ(i72.popcount(), 47U);
+
+ // Ensure we handle large shifts of multi-word.
+ const APSInt signmin128(
+ APSInt(APInt::getSignedMinValue(128), /*isUnsigned*/ false));
+ EXPECT_TRUE((signmin128 >> 128).isAllOnes());
+
+ // Ensure we handle large shifts of multi-word.
+ const APSInt umax128(
+ APSInt(APInt::getSignedMaxValue(128), /*isUnsigned*/ false));
+ EXPECT_EQ(umax128 >> 128, 0);
+}
+
+TEST(APSIntTest, Fshl) {
+ // Unsigned
+ EXPECT_EQ(APSIntOps::fshl(APSInt(APInt(8, 0)), APSInt(APInt(8, 255)),
+ APSInt(APInt(8, 8)))
+ .getExtValue(),
+ 0);
+ EXPECT_EQ(APSIntOps::fshl(APSInt(APInt(8, 255)), APSInt(APInt(8, 0)),
+ APSInt(APInt(8, 8)))
+ .getExtValue(),
+ 255);
+ EXPECT_EQ(APSIntOps::fshl(APSInt(APInt(8, 255)), APSInt(APInt(8, 0)),
+ APSInt(APInt(8, 15)))
+ .getExtValue(),
+ 128);
+ EXPECT_EQ(APSIntOps::fshl(APSInt(APInt(8, 15)), APSInt(APInt(8, 15)),
+ APSInt(APInt(8, 11)))
+ .getExtValue(),
+ 120);
+ EXPECT_EQ(APSIntOps::fshl(APSInt(APInt(8, 2)), APSInt(APInt(8, 1)),
+ APSInt(APInt(8, 3)))
+ .getExtValue(),
+ 16);
+ // Signed
+ EXPECT_EQ(APSIntOps::fshl(APSInt(APInt(32, 0), false),
+ APSInt(APInt(32, 2147483647), false),
+ APSInt(APInt(32, 32), false))
+ .getExtValue(),
+ 0);
+ EXPECT_EQ(APSIntOps::fshl(APSInt(APInt(64, 1), false),
+ APSInt(APInt(64, 2), false),
+ APSInt(APInt(64, 3), false))
+ .getExtValue(),
+ 8);
+}
+
+TEST(APSIntTest, Fshr) {
+ // Unsigned
+ EXPECT_EQ(APSIntOps::fshr(APSInt(APInt(8, 0)), APSInt(APInt(8, 255)),
+ APSInt(APInt(8, 8)))
+ .getExtValue(),
+ 255);
+ EXPECT_EQ(APSIntOps::fshr(APSInt(APInt(8, 255)), APSInt(APInt(8, 0)),
+ APSInt(APInt(8, 8)))
+ .getExtValue(),
+ 0);
+ EXPECT_EQ(APSIntOps::fshr(APSInt(APInt(8, 255)), APSInt(APInt(8, 0)),
+ APSInt(APInt(8, 15)))
+ .getExtValue(),
+ 254);
+ EXPECT_EQ(APSIntOps::fshr(APSInt(APInt(8, 15)), APSInt(APInt(8, 15)),
+ APSInt(APInt(8, 11)))
+ .getExtValue(),
+ 225);
+ EXPECT_EQ(APSIntOps::fshr(APSInt(APInt(8, 1)), APSInt(APInt(8, 2)),
+ APSInt(APInt(8, 3)))
+ .getExtValue(),
+ 32);
+ // Signed
+ EXPECT_EQ(APSIntOps::fshr(APSInt(APInt(64, 0), false),
+ APSInt(APInt(64, 9223372036854775807), false),
+ APSInt(APInt(64, 64), false))
+ .getExtValue(),
+ 9223372036854775807);
+ EXPECT_EQ(APSIntOps::fshr(APSInt(APInt(64, 1), false),
+ APSInt(APInt(64, 2), false),
+ APSInt(APInt(64, 3), false))
+ .getExtValue(),
+ 2305843009213693952);
+}
+
} // end anonymous namespace
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