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[APInt] Add APIntOps::absdiff to compute the absolute difference of 2 unsigned values (#82255)

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Equivalent to "umax(A, B) - umin(A, B)"

First step towards adding knownbits support for absdiff patterns for #81765
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Simon Pilgrim 2024-02-19 15:59:21 +00:00 committed by GitHub
parent 1789dc2fbc
commit 73f76cda1f
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2 changed files with 39 additions and 0 deletions
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5
llvm/include/llvm/ADT/APInt.h
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@ -2187,6 +2187,11 @@ inline const APInt &umax(const APInt &A, const APInt &B) {
return A.ugt(B) ? A : B;
}
/// Determine the absolute difference of two APInts considered to be unsigned.
inline const APInt absdiff(const APInt &A, const APInt &B) {
return A.uge(B) ? (A - B) : (B - A);
}
/// Compute GCD of two unsigned APInt values.
///
/// This function returns the greatest common divisor of the two APInt values

34
llvm/unittests/ADT/APIntTest.cpp
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@ -2497,6 +2497,40 @@ TEST(APIntTest, clearLowBits) {
EXPECT_EQ(16u, i32hi16.popcount());
}
TEST(APIntTest, AbsDiff) {
using APIntOps::absdiff;
APInt MaxU1(1, 1, false);
APInt MinU1(1, 0, false);
EXPECT_EQ(1u, absdiff(MaxU1, MinU1).getZExtValue());
EXPECT_EQ(1u, absdiff(MinU1, MaxU1).getZExtValue());
APInt MaxU4(4, 15, false);
APInt MinU4(4, 0, false);
EXPECT_EQ(15u, absdiff(MaxU4, MinU4).getZExtValue());
EXPECT_EQ(15u, absdiff(MinU4, MaxU4).getZExtValue());
APInt MaxS8(8, 127, true);
APInt MinS8(8, -128, true);
EXPECT_EQ(1u, absdiff(MaxS8, MinS8).getZExtValue());
EXPECT_EQ(1u, absdiff(MinS8, MaxS8).getZExtValue());
APInt MaxU16(16, 65535, false);
APInt MinU16(16, 0, false);
EXPECT_EQ(65535u, absdiff(MaxU16, MinU16).getZExtValue());
EXPECT_EQ(65535u, absdiff(MinU16, MaxU16).getZExtValue());
APInt MaxS16(16, 32767, true);
APInt MinS16(16, -32768, true);
APInt ZeroS16(16, 0, true);
EXPECT_EQ(1u, absdiff(MaxS16, MinS16).getZExtValue());
EXPECT_EQ(1u, absdiff(MinS16, MaxS16).getZExtValue());
EXPECT_EQ(32768u, absdiff(ZeroS16, MinS16));
EXPECT_EQ(32768u, absdiff(MinS16, ZeroS16));
EXPECT_EQ(32767u, absdiff(ZeroS16, MaxS16));
EXPECT_EQ(32767u, absdiff(MaxS16, ZeroS16));
}
TEST(APIntTest, GCD) {
using APIntOps::GreatestCommonDivisor;