Commit Graph

6 Commits

Author SHA1 Message Date
Benjamin Kramer 1f4dfbbcb0 DAGCombine add (sext i1), X into sub X, (zext i1) if sext from i1 is illegal. The latter usually compiles into smaller code.
example code:
unsigned foo(unsigned x, unsigned y) {
  if (x != 0) y--;
  return y;
}

before:
  _foo:                           ## @foo
    cmpl  $1, 4(%esp)             ## encoding: [0x83,0x7c,0x24,0x04,0x01]
    sbbl  %eax, %eax              ## encoding: [0x19,0xc0]
    notl  %eax                    ## encoding: [0xf7,0xd0]
    addl  8(%esp), %eax           ## encoding: [0x03,0x44,0x24,0x08]
    ret                           ## encoding: [0xc3]

after:
  _foo:                           ## @foo
    cmpl  $1, 4(%esp)             ## encoding: [0x83,0x7c,0x24,0x04,0x01]
    movl  8(%esp), %eax           ## encoding: [0x8b,0x44,0x24,0x08]
    adcl  $-1, %eax               ## encoding: [0x83,0xd0,0xff]
    ret                           ## encoding: [0xc3]

llvm-svn: 122455
2010-12-22 23:17:45 +00:00
Chris Lattner 5c00d41688 now that addc/adde are gone, "ADDC" in the X86 backend uses EFLAGS results,
the same as setcc.  Optimize ADDC(0,0,FLAGS) -> SET_CARRY(FLAGS).  This is
a step towards finishing off PR5443.  In the testcase in that bug we now  get:

	movq	%rdi, %rax
	addq	%rsi, %rax
	sbbq	%rcx, %rcx
	testb	$1, %cl
	setne	%dl
	ret

instead of:

	movq	%rdi, %rax
	addq	%rsi, %rax
	movl	$0, %ecx
	adcq	$0, %rcx
	testq	%rcx, %rcx
	setne	%dl
	ret

llvm-svn: 122219
2010-12-20 01:37:09 +00:00
Chris Lattner 46b9efcad7 We lower setb to sbb with the hope that the and will go away, when it
doesn't, match it back to setb.

On a 64-bit version of the testcase before we'd get:

	movq	%rdi, %rax
	addq	%rsi, %rax
	sbbb	%dl, %dl
	andb	$1, %dl
	ret

now we get:

	movq	%rdi, %rax
	addq	%rsi, %rax
	setb	%dl
	ret

llvm-svn: 122217
2010-12-20 01:16:03 +00:00
Chris Lattner 933509287b merge a target-specific add test into x86 directory.
llvm-svn: 95654
2010-02-09 06:35:50 +00:00
Chris Lattner 015ecd85d4 merge another test in, drop the trivially constant folded cases.
llvm-svn: 95653
2010-02-09 06:33:27 +00:00
Chris Lattner c77b9eb31c consolidate and filecheckize two tests.
llvm-svn: 95652
2010-02-09 06:24:00 +00:00