llvm-6502/test/CodeGen/X86/code_placement_outline_optional_branches.ll
Daniel Jasper 70b146b25e [MBP] Don't outline short optional branches
With the option -outline-optional-branches, LLVM will place optional
branches out of line (more details on r231230).

With this patch, this is not done for short optional branches. A short
optional branch is a branch containing a single block with an
instruction count below a certain threshold (defaulting to 3). Still
everything is guarded under -outline-optional-branches).

Outlining a short branch can't significantly improve code locality. It
can however decrease performance because of the additional jmp and in
cases where the optional branch is hot. This fixes a compile time
regression I have observed in a benchmark.

Review: http://reviews.llvm.org/D8108

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232802 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-20 10:00:37 +00:00

78 lines
1.5 KiB
LLVM

; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux < %s | FileCheck %s -check-prefix=CHECK
; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux -outline-optional-branches < %s | FileCheck %s -check-prefix=CHECK-OUTLINE
define void @foo(i32 %t1, i32 %t2, i32 %t3) {
; Test that we lift the call to 'c' up to immediately follow the call to 'b'
; when we disable the cfg conflict check.
;
; CHECK-LABEL: foo:
; CHECK: callq a
; CHECK: callq a
; CHECK: callq a
; CHECK: callq a
; CHECK: callq b
; CHECK: callq c
; CHECK: callq d
; CHECK: callq e
; CHECK: callq f
;
; CHECK-OUTLINE-LABEL: foo:
; CHECK-OUTLINE: callq b
; CHECK-OUTLINE: callq c
; CHECK-OUTLINE: callq d
; CHECK-OUTLINE: callq e
; CHECK-OUTLINE: callq f
; CHECK-OUTLINE: callq a
; CHECK-OUTLINE: callq a
; CHECK-OUTLINE: callq a
; CHECK-OUTLINE: callq a
entry:
%cmp = icmp eq i32 %t1, 0
br i1 %cmp, label %if.then, label %if.end
if.then:
call void @a()
call void @a()
call void @a()
call void @a()
br label %if.end
if.end:
call void @b()
br label %hotbranch
hotbranch:
%cmp2 = icmp eq i32 %t2, 0
br i1 %cmp2, label %if.then2, label %if.end2, !prof !1
if.then2:
call void @c()
br label %if.end2
if.end2:
call void @d()
br label %shortbranch
shortbranch:
%cmp3 = icmp eq i32 %t3, 0
br i1 %cmp3, label %if.then3, label %if.end3
if.then3:
call void @e()
br label %if.end3
if.end3:
call void @f()
ret void
}
declare void @a()
declare void @b()
declare void @c()
declare void @d()
declare void @e()
declare void @f()
!1 = !{!"branch_weights", i32 64, i32 4}