insns.def (opt_plus): use - 1 instead of & (~1) to allow
compilers to use x86 LEA instruction (3 operand).
Even if 3 operand LEA's latency is 3 cycle after SandyBridge,
it reduces code size and can be faster because of super scalar.
insns.def (opt_plus): calculate and use rb_int2big.
On positive Fixnum overflow, recv - 1 + obj doesn't carry
because recv's msb and obj's msb are 0, and resulted msb is 1.
Therefore simply rshift and cast as signed long works fine.
On negative Fixnum overflow, it will carry because both arguments'
msb are 1, and resulted msb is also 1.
In this case it needs to restore carried sign bit after rshift.
Added by naruse (Yui NARUSE) about 9 years ago
insns.def (opt_plus): use
- 1instead of& (~1)to allowcompilers to use x86 LEA instruction (3 operand).
Even if 3 operand LEA's latency is 3 cycle after SandyBridge,
it reduces code size and can be faster because of super scalar.
insns.def (opt_plus): calculate and use rb_int2big.
On positive Fixnum overflow,
recv - 1 + objdoesn't carrybecause recv's msb and obj's msb are 0, and resulted msb is 1.
Therefore simply rshift and cast as signed long works fine.
On negative Fixnum overflow, it will carry because both arguments'
msb are 1, and resulted msb is also 1.
In this case it needs to restore carried sign bit after rshift.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55515 b2dd03c8-39d4-4d8f-98ff-823fe69b080e