3 Commits

Author	SHA1	Message	Date
Chris Lattner	64a1a9f502	third time around: instead of disabling this completely, ... only disable it if we don't know it will be obviously profitable. Still fixme, but less so. :) llvm-svn: 44658	2007-12-06 07:47:55 +00:00
Chris Lattner	bb5fb18af8	Actually, disable this code for now. More analysis and improvements to ... the X86 backend are needed before this should be enabled by default. llvm-svn: 44657	2007-12-06 07:44:31 +00:00
Chris Lattner	c467b49c96	implement a readme entry, compiling the code into: ... _foo: movl $12, %eax andl 4(%esp), %eax movl _array(%eax), %eax ret instead of: _foo: movl 4(%esp), %eax shrl $2, %eax andl $3, %eax movl _array(,%eax,4), %eax ret As it turns out, this triggers all the time, in a wide variety of situations, for example, I see diffs like this in various programs: - movl 8(%eax), %eax - shll $2, %eax - andl $1020, %eax - movl (%esi,%eax), %eax + movzbl 8(%eax), %eax + movl (%esi,%eax,4), %eax - shll $2, %edx - andl $1020, %edx - movl (%edi,%edx), %edx + andl $255, %edx + movl (%edi,%edx,4), %edx Unfortunately, I also see stuff like this, which can be fixed in the X86 backend: - andl $85, %ebx - addl _bit_count(,%ebx,4), %ebp + shll $2, %ebx + andl $340, %ebx + addl _bit_count(%ebx), %ebp llvm-svn: 44656	2007-12-06 07:33:36 +00:00