more clear what exactly is missing.

llvm-svn: 105934

llvm-svn: 105674

llvm-svn: 105303

llvm-svn: 78511

llvm-svn: 64535

llvm-svn: 55920

argument. The x86-64 ABI requires the incoming value of %rdi to
be copied to %rax on exit from a function that is returning a
large C struct.

Also, add a README-X86-64 entry detailing the missed optimization
opportunity and proposing an alternative approach.

llvm-svn: 50075

stack slot and store if the  SINT_TO_FP is actually legal.  This allows
us to compile:

double a(double b) {return (unsigned)b;}

to:

_a:
	cvttsd2siq	%xmm0, %rax
	movl	%eax, %eax
	cvtsi2sdq	%rax, %xmm0
	ret

instead of:

_a:
	subq	$8, %rsp
	cvttsd2siq	%xmm0, %rax
	movl	%eax, %eax
	cvtsi2sdq	%rax, %xmm0
	addq	$8, %rsp
	ret

crazy.

llvm-svn: 47660

llvm-svn: 47659

_test:
	movl	%edi, %eax
	ret

instead of:

_test:
        movl    $4294967295, %ecx
        movq    %rdi, %rax
        andq    %rcx, %rax
        ret

It would be great to write this as a Pat pattern that used subregs 
instead of a 'pseudo' instruction, but I don't know how to do that
in td files.

llvm-svn: 47658

llvm-svn: 47652

divb / mulb outputs to ah. Under x86-64 it's not legal to read ah if the instruction requires a rex prefix (i.e. outputs to r8b, etc.). So issue shift right by 8 on AX and then truncate it to 8 bits instead.

llvm-svn: 40972

llvm-svn: 35430

- Re-enable some codegen niceties for X86-64 static relocation model codegen.
- Clean ups, etc.

llvm-svn: 32238

llvm-svn: 32214

llvm-svn: 30177