successors), and make island block movement more general.

This compiles CodeGen/X86/2006-04-27-ISelFoldingBug.ll to:

_loadAndRLEsource_no_exit_2E_1_label_2E_0:
        subl $8, %esp
        movl %esi, 4(%esp)
        movl %ebx, (%esp)
        movl 16(%esp), %eax
        movl 12(%esp), %ecx
LBB1_3: #label.0
        movl _last, %edx
        movl %edx, %esi
        incl %esi
        movl %esi, _last
        movl %ecx, %ebx
        # TRUNCATE movb %bl, %bl
        movl _block, %esi
        movb %bl, 1(%esi,%edx)
        cmpl %eax, _last
        jge LBB1_2      #codeRepl5.exitStub
LBB1_4: #label.0
        cmpl $257, %ecx
        je LBB1_2       #codeRepl5.exitStub
LBB1_1: #label.0.no_exit.1_crit_edge.exitStub
        movl $1, %eax
        movl (%esp), %ebx
        movl 4(%esp), %esi
        addl $8, %esp
        ret
LBB1_2: #codeRepl5.exitStub
        xorl %eax, %eax
        movl (%esp), %ebx
        movl 4(%esp), %esi
        addl $8, %esp
        ret

instead of:

_loadAndRLEsource_no_exit_2E_1_label_2E_0:
        subl $8, %esp
        movl %esi, 4(%esp)
        movl %ebx, (%esp)
        movl 16(%esp), %eax
        movl 12(%esp), %ecx
        jmp LBB1_3      #label.0
LBB1_1: #label.0.no_exit.1_crit_edge.exitStub
        movl $1, %eax
        movl (%esp), %ebx
        movl 4(%esp), %esi
        addl $8, %esp
        ret
LBB1_2: #codeRepl5.exitStub
        xorl %eax, %eax
        movl (%esp), %ebx
        movl 4(%esp), %esi
        addl $8, %esp
        ret
LBB1_3: #label.0
        movl _last, %edx
        movl %edx, %esi
        incl %esi
        movl %esi, _last
        movl %ecx, %ebx
        # TRUNCATE movb %bl, %bl
        movl _block, %esi
        movb %bl, 1(%esi,%edx)
        cmpl %eax, _last
        jge LBB1_2      #codeRepl5.exitStub
LBB1_4: #label.0
        cmpl $257, %ecx
        jne LBB1_1      #label.0.no_exit.1_crit_edge.exitStub
        jmp LBB1_2      #codeRepl5.exitStub

... which is much better layout :)

llvm-svn: 31282

llvm-svn: 31281

llvm-svn: 31280

used by comparisons in the main block.

llvm-svn: 31279

llvm-svn: 31278

llvm-svn: 31277

llvm-svn: 31276

llvm-svn: 31275

edges whose destinations are not phi nodes don't bother us.  Also, share
split edges, since the split edge can't have a phi.  This significantly
reduces the complexity of generated code in some cases.

llvm-svn: 31274

jump tables that are dead.

llvm-svn: 31273

llvm-svn: 31272

llvm-svn: 31271

llvm-svn: 31270

llvm-svn: 31269

llvm-svn: 31268

llvm-svn: 31267

llvm-svn: 31266

llvm-svn: 31265

llvm-svn: 31264

the pred block doesn't fall through into them if it's a jumptable.

llvm-svn: 31263

llvm-svn: 31262

llvm-svn: 31261

being inserted on unsplit critical edges, which introduces (sometimes large
amounts of) partially dead spill code.

This also fixes PR925 + CodeGen/Generic/switch-crit-edge-constant.ll

llvm-svn: 31260

llvm-svn: 31259

llvm-svn: 31258

llvm-svn: 31257

llvm-svn: 31256

llvm-svn: 31255

llvm-svn: 31254

llvm-svn: 31253

llvm-svn: 31252

Clarify the test.

llvm-svn: 31251

llvm-svn: 31250

llvm-svn: 31249

llvm-svn: 31248

llvm-svn: 31247

llvm-svn: 31246

llvm-svn: 31245

llvm-svn: 31244

llvm-svn: 31243