llvm-6502/test/CodeGen/X86/jump_sign.ll
Manman Ren 73c2f7f5ed X86: peephole optimization to remove cmp instruction
This patch will optimize the following:
  sub r1, r3
  cmp r3, r1 or cmp r1, r3
  bge L1
TO
  sub r1, r3
  bge L1 or ble L1

If the branch instruction can use flag from "sub", then we can eliminate
the "cmp" instruction.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157831 91177308-0d34-0410-b5e6-96231b3b80d8
2012-06-01 19:49:33 +00:00

116 lines
2.3 KiB
LLVM

; RUN: llc < %s -march=x86 -mcpu=pentiumpro | FileCheck %s
define i32 @f(i32 %X) {
entry:
; CHECK: f:
; CHECK: jns
%tmp1 = add i32 %X, 1 ; <i32> [#uses=1]
%tmp = icmp slt i32 %tmp1, 0 ; <i1> [#uses=1]
br i1 %tmp, label %cond_true, label %cond_next
cond_true: ; preds = %entry
%tmp2 = tail call i32 (...)* @bar( ) ; <i32> [#uses=0]
br label %cond_next
cond_next: ; preds = %cond_true, %entry
%tmp3 = tail call i32 (...)* @baz( ) ; <i32> [#uses=0]
ret i32 undef
}
declare i32 @bar(...)
declare i32 @baz(...)
; rdar://10633221
; rdar://11355268
define i32 @g(i32 %a, i32 %b) nounwind {
entry:
; CHECK: g:
; CHECK-NOT: test
; CHECK: cmovs
%sub = sub nsw i32 %a, %b
%cmp = icmp sgt i32 %sub, 0
%cond = select i1 %cmp, i32 %sub, i32 0
ret i32 %cond
}
; rdar://10734411
define i32 @h(i32 %a, i32 %b) nounwind {
entry:
; CHECK: h:
; CHECK-NOT: cmp
; CHECK: cmov
; CHECK-NOT: movl
; CHECK: ret
%cmp = icmp slt i32 %b, %a
%sub = sub nsw i32 %a, %b
%cond = select i1 %cmp, i32 %sub, i32 0
ret i32 %cond
}
define i32 @i(i32 %a, i32 %b) nounwind {
entry:
; CHECK: i:
; CHECK-NOT: cmp
; CHECK: cmov
; CHECK-NOT: movl
; CHECK: ret
%cmp = icmp sgt i32 %a, %b
%sub = sub nsw i32 %a, %b
%cond = select i1 %cmp, i32 %sub, i32 0
ret i32 %cond
}
define i32 @j(i32 %a, i32 %b) nounwind {
entry:
; CHECK: j:
; CHECK-NOT: cmp
; CHECK: cmov
; CHECK-NOT: movl
; CHECK: ret
%cmp = icmp ugt i32 %a, %b
%sub = sub i32 %a, %b
%cond = select i1 %cmp, i32 %sub, i32 0
ret i32 %cond
}
define i32 @k(i32 %a, i32 %b) nounwind {
entry:
; CHECK: k:
; CHECK-NOT: cmp
; CHECK: cmov
; CHECK-NOT: movl
; CHECK: ret
%cmp = icmp ult i32 %b, %a
%sub = sub i32 %a, %b
%cond = select i1 %cmp, i32 %sub, i32 0
ret i32 %cond
}
; redundant cmp instruction
define i32 @l(i32 %a, i32 %b) nounwind {
entry:
; CHECK: l:
; CHECK-NOT: cmp
%cmp = icmp slt i32 %b, %a
%sub = sub nsw i32 %a, %b
%cond = select i1 %cmp, i32 %sub, i32 %a
ret i32 %cond
}
define i32 @m(i32 %a, i32 %b) nounwind {
entry:
; CHECK: m:
; CHECK-NOT: cmp
%cmp = icmp sgt i32 %a, %b
%sub = sub nsw i32 %a, %b
%cond = select i1 %cmp, i32 %b, i32 %sub
ret i32 %cond
}
; rdar://11540023
define i64 @n(i64 %x, i64 %y) nounwind {
entry:
; CHECK: n:
; CHECK-NOT: sub
; CHECK: cmp
%sub = sub nsw i64 %x, %y
%cmp = icmp slt i64 %sub, 0
%y.x = select i1 %cmp, i64 %y, i64 %x
ret i64 %y.x
}