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[libc][math] Fix subtraction of infinity in fputil::add_or_sub #152017

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Merged
merged 4 commits into from
Aug 4, 2025
Merged

[libc][math] Fix subtraction of infinity in fputil::add_or_sub #152017

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7678bcd
fix: consider IsSub in finite - infinity case
krishna2803 Aug 4, 2025
fd3e5ec
chore: add unit tests for x - inf
krishna2803 Aug 4, 2025
30dca29
fix: add missing return
krishna2803 Aug 4, 2025
d6575f9
chore: add more unit tests for Sub and Add
krishna2803 Aug 4, 2025
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8 changes: 6 additions & 2 deletions libc/src/__support/FPUtil/generic/add_sub.h
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Original file line number Diff line number Diff line change
Expand Up @@ -87,8 +87,12 @@ add_or_sub(InType x, InType y) {
return OutFPBits::inf(x_bits.sign()).get_val();
}

if (y_bits.is_inf())
return OutFPBits::inf(y_bits.sign()).get_val();
if (y_bits.is_inf()) {
if constexpr (IsSub)
return OutFPBits::inf(y_bits.sign().negate()).get_val();
else
return OutFPBits::inf(y_bits.sign()).get_val();
}

if (x_bits.is_zero()) {
if (y_bits.is_zero()) {
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4 changes: 4 additions & 0 deletions libc/test/src/math/smoke/AddTest.h
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Expand Up @@ -47,6 +47,10 @@ class AddTest : public LIBC_NAMESPACE::testing::FEnvSafeTest {
EXPECT_FP_EQ(neg_inf, func(in.neg_inf, in.zero));
EXPECT_FP_EQ(inf, func(in.inf, in.neg_zero));
EXPECT_FP_EQ(neg_inf, func(in.neg_inf, in.neg_zero));
EXPECT_FP_EQ(inf, func(in.zero, in.inf));
EXPECT_FP_EQ(inf, func(in.neg_zero, in.inf));
EXPECT_FP_EQ(neg_inf, func(in.zero, in.neg_inf));
EXPECT_FP_EQ(neg_inf, func(in.neg_zero, in.neg_inf));
}

void test_invalid_operations(AddFunc func) {
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4 changes: 4 additions & 0 deletions libc/test/src/math/smoke/SubTest.h
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Expand Up @@ -47,6 +47,10 @@ class SubTest : public LIBC_NAMESPACE::testing::FEnvSafeTest {
EXPECT_FP_EQ(neg_inf, func(in.neg_inf, in.zero));
EXPECT_FP_EQ(inf, func(in.inf, in.neg_zero));
EXPECT_FP_EQ(neg_inf, func(in.neg_inf, in.neg_zero));
EXPECT_FP_EQ(neg_inf, func(in.zero, in.inf));
EXPECT_FP_EQ(neg_inf, func(in.neg_zero, in.inf));
EXPECT_FP_EQ(inf, func(in.zero, in.neg_inf));
EXPECT_FP_EQ(inf, func(in.neg_zero, in.neg_inf));
}

void test_invalid_operations(SubFunc func) {
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