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ADT: Fix that APSInt's string constructor claims it requires 5 bits to store a zero 

Summary:

When constructing an APSInt from a string, the constructor doesn't correctly
truncate the bit width of the result if the passed in string was "0" (or any
alternative way to express 0 like "-0" or "000"). Instead of 1 (which is the
smallest allowed bit width) it returns an APSInt with a bit width of 5.

The reason is that the constructor checks that it never truncates the result to
the invalid bit width of 0, so when it calculates that storing a "0" doesn't
require any bits it just keeps the original overestimated bit width (which
happens to be 5).

This patch just sets the bit width of the result to 1 if the required bit width
is 0.

Reviewers: arphaman, dexonsmith

Reviewed By: dexonsmith

Subscribers: hiraditya, dexonsmith, JDevlieghere, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D81329
This commit is contained in:
Raphael Isemann 2020-06-10 16:35:42 +02:00
parent de522035b9
commit f60e319419
2 changed files with 27 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
llvm/lib/Support/APSInt.cpp
View File

@ -26,14 +26,14 @@ APSInt::APSInt(StringRef Str) {
APInt Tmp(NumBits, Str, /*radix=*/10);
if (Str[0] == '-') {
unsigned MinBits = Tmp.getMinSignedBits();
if (MinBits > 0 && MinBits < NumBits)
Tmp = Tmp.trunc(MinBits);
if (MinBits < NumBits)
Tmp = Tmp.trunc(std::max<unsigned>(1, MinBits));
*this = APSInt(Tmp, /*isUnsigned=*/false);
return;
}
unsigned ActiveBits = Tmp.getActiveBits();
if (ActiveBits > 0 && ActiveBits < NumBits)
Tmp = Tmp.trunc(ActiveBits);
if (ActiveBits < NumBits)
Tmp = Tmp.trunc(std::max<unsigned>(1, ActiveBits));
*this = APSInt(Tmp, /*isUnsigned=*/true);
}

23
llvm/unittests/ADT/APSIntTest.cpp
View File

@ -150,6 +150,29 @@ TEST(APSIntTest, FromString) {
EXPECT_EQ(APSInt("-1234").getExtValue(), -1234);
}
TEST(APSIntTest, FromStringBitWidth) {
EXPECT_EQ(APSInt("0").getBitWidth(), 1U);
EXPECT_EQ(APSInt("000").getBitWidth(), 1U);
EXPECT_EQ(APSInt("1").getBitWidth(), 1U);
EXPECT_EQ(APSInt("2").getBitWidth(), 2U);
EXPECT_EQ(APSInt("3").getBitWidth(), 2U);
EXPECT_EQ(APSInt("003").getBitWidth(), 2U);
EXPECT_EQ(APSInt("15").getBitWidth(), 4U);
EXPECT_EQ(APSInt("16").getBitWidth(), 5U);
EXPECT_EQ(APSInt("17").getBitWidth(), 5U);
EXPECT_EQ(APSInt("-0").getBitWidth(), 1U);
EXPECT_EQ(APSInt("-000").getBitWidth(), 1U);
EXPECT_EQ(APSInt("-1").getBitWidth(), 1U);
EXPECT_EQ(APSInt("-2").getBitWidth(), 2U);
EXPECT_EQ(APSInt("-3").getBitWidth(), 3U);
EXPECT_EQ(APSInt("-003").getBitWidth(), 3U);
EXPECT_EQ(APSInt("-5").getBitWidth(), 4U);
EXPECT_EQ(APSInt("-15").getBitWidth(), 5U);
EXPECT_EQ(APSInt("-16").getBitWidth(), 5U);
EXPECT_EQ(APSInt("-17").getBitWidth(), 6U);
}
#if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG)
TEST(APSIntTest, StringDeath) {