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[demangler][NFC] Utility header cleanups 

a) Using a do...while loop in the number formatter means we do not
have to special case zero.

b) Let's use 'if (auto size = ...) {}' for appending to the output
buffer.

c) We should also be using memcpy there, not memmove -- the string
being appended is never part of the current buffer.

d) Let's put all the operator<< functions together.

e) I find 'if (cond) frob(..., true) ; elseOD frob(..., false)'
somewhat confusing.  Let's just use std::abs in the signed integer
printer and let CSE decide about the duplicate < 0 testing.

f) Let's have as many as possible return *this.  That's both more
consistent, and allows tailcalls in some cases (the actual number
formatter has a local array though).

These changes removed around 100 bytes from the demangler's
instructions on x86_64.

Reviewed By: ChuanqiXu

Differential Revision: https://reviews.llvm.org/D119176
This commit is contained in:
Nathan Sidwell 2022-02-07 10:08:18 -08:00
parent 18834dca2d
commit f0ef708dc1
2 changed files with 32 additions and 52 deletions
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42
libcxxabi/src/demangle/Utility.h
View File

@ -45,25 +45,21 @@ class OutputBuffer {
}
}
void writeUnsigned(uint64_t N, bool isNeg = false) {
// Handle special case...
if (N == 0) {
*this << '0';
return;
}
OutputBuffer &writeUnsigned(uint64_t N, bool isNeg = false) {
std::array<char, 21> Temp;
char *TempPtr = Temp.data() + Temp.size();
while (N) {
// Output at least one character.
do {
*--TempPtr = char('0' + N % 10);
N /= 10;
}
} while (N);
// Add negative sign...
// Add negative sign.
if (isNeg)
*--TempPtr = '-';
this->operator<<(StringView(TempPtr, Temp.data() + Temp.size()));
return operator+=(StringView(TempPtr, Temp.data() + Temp.size()));
}
public:
@ -82,12 +78,11 @@ public:
unsigned CurrentPackMax = std::numeric_limits<unsigned>::max();
OutputBuffer &operator+=(StringView R) {
size_t Size = R.size();
if (Size == 0)
return *this;
grow(Size);
std::memmove(Buffer + CurrentPosition, R.begin(), Size);
CurrentPosition += Size;
if (size_t Size = R.size()) {
grow(Size);
std::memcpy(Buffer + CurrentPosition, R.begin(), Size);
CurrentPosition += Size;
}
return *this;
}
@ -97,8 +92,6 @@ public:
return *this;
}
OutputBuffer &operator<<(StringView R) { return (*this += R); }
OutputBuffer prepend(StringView R) {
size_t Size = R.size();
@ -110,19 +103,16 @@ public:
return *this;
}
OutputBuffer &operator<<(StringView R) { return (*this += R); }
OutputBuffer &operator<<(char C) { return (*this += C); }
OutputBuffer &operator<<(long long N) {
if (N < 0)
writeUnsigned(static_cast<unsigned long long>(-N), true);
else
writeUnsigned(static_cast<unsigned long long>(N));
return *this;
return writeUnsigned(static_cast<unsigned long long>(std::abs(N)), N < 0);
}
OutputBuffer &operator<<(unsigned long long N) {
writeUnsigned(N, false);
return *this;
return writeUnsigned(N, false);
}
OutputBuffer &operator<<(long N) {

42
llvm/include/llvm/Demangle/Utility.h
View File

@ -45,25 +45,21 @@ class OutputBuffer {
}
}
void writeUnsigned(uint64_t N, bool isNeg = false) {
// Handle special case...
if (N == 0) {
*this << '0';
return;
}
OutputBuffer &writeUnsigned(uint64_t N, bool isNeg = false) {
std::array<char, 21> Temp;
char *TempPtr = Temp.data() + Temp.size();
while (N) {
// Output at least one character.
do {
*--TempPtr = char('0' + N % 10);
N /= 10;
}
} while (N);
// Add negative sign...
// Add negative sign.
if (isNeg)
*--TempPtr = '-';
this->operator<<(StringView(TempPtr, Temp.data() + Temp.size()));
return operator+=(StringView(TempPtr, Temp.data() + Temp.size()));
}
public:
@ -82,12 +78,11 @@ public:
unsigned CurrentPackMax = std::numeric_limits<unsigned>::max();
OutputBuffer &operator+=(StringView R) {
size_t Size = R.size();
if (Size == 0)
return *this;
grow(Size);
std::memmove(Buffer + CurrentPosition, R.begin(), Size);
CurrentPosition += Size;
if (size_t Size = R.size()) {
grow(Size);
std::memcpy(Buffer + CurrentPosition, R.begin(), Size);
CurrentPosition += Size;
}
return *this;
}
@ -97,8 +92,6 @@ public:
return *this;
}
OutputBuffer &operator<<(StringView R) { return (*this += R); }
OutputBuffer prepend(StringView R) {
size_t Size = R.size();
@ -110,19 +103,16 @@ public:
return *this;
}
OutputBuffer &operator<<(StringView R) { return (*this += R); }
OutputBuffer &operator<<(char C) { return (*this += C); }
OutputBuffer &operator<<(long long N) {
if (N < 0)
writeUnsigned(static_cast<unsigned long long>(-N), true);
else
writeUnsigned(static_cast<unsigned long long>(N));
return *this;
return writeUnsigned(static_cast<unsigned long long>(std::abs(N)), N < 0);
}
OutputBuffer &operator<<(unsigned long long N) {
writeUnsigned(N, false);
return *this;
return writeUnsigned(N, false);
}
OutputBuffer &operator<<(long N) {