Microoptimize Twine's with unsigned and int to not pin their value to
the stack. This saves stack space in common cases and allows mem2reg
in the caller. A simple example is:
void foo(const Twine &);
void bar(int x) {
foo("xyz: " + Twine(x));
}
Before:
__Z3bari:
subq $40, %rsp
movl %edi, 36(%rsp)
leaq L_.str3(%rip), %rax
leaq 36(%rsp), %rcx
leaq 8(%rsp), %rdi
movq %rax, 8(%rsp)
movq %rcx, 16(%rsp)
movb $3, 24(%rsp)
movb $7, 25(%rsp)
callq __Z3fooRKN4llvm5TwineE
addq $40, %rsp
ret
After:
__Z3bari:
subq $24, %rsp
leaq L_.str3(%rip), %rax
movq %rax, (%rsp)
movslq %edi, %rax
movq %rax, 8(%rsp)
movb $3, 16(%rsp)
movb $7, 17(%rsp)
leaq (%rsp), %rdi
callq __Z3fooRKN4llvm5TwineE
addq $24, %rsp
ret
It saves 16 bytes of stack and one instruction in this case.
llvm-svn: 103107
- Provides static constructors for doing number to string conversions without
using temporaries.
- There are several ways to do this, I think given the Twine constraints this
is the simplest one.
- One FIXME for fast number -> hex conversion.
- Added another comment on one last major bit of perf work Twines need, which
is to make raw_svector_ostream more efficient.
llvm-svn: 77445
