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Add a flag to experiment with outlining optional branches. In a CFG with the edges A->B->C and A->C, B is an optional branch. LLVM's default behavior is to lay the blocks out naturally, i.e. A, B, C, in order to improve code locality and fallthroughs. However, if a function contains many of those optional branches only a few of which are taken, this leads to a lot of unnecessary icache misses. Moving B out of line can work around this. Review: http://reviews.llvm.org/D7719 llvm-svn: 231230
2015-03-04 19:05:34 +08:00
; 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
[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 llvm-svn: 232802
2015-03-20 18:00:37 +08:00
define void @foo(i32 %t1, i32 %t2, i32 %t3) {
Add a flag to experiment with outlining optional branches. In a CFG with the edges A->B->C and A->C, B is an optional branch. LLVM's default behavior is to lay the blocks out naturally, i.e. A, B, C, in order to improve code locality and fallthroughs. However, if a function contains many of those optional branches only a few of which are taken, this leads to a lot of unnecessary icache misses. Moving B out of line can work around this. Review: http://reviews.llvm.org/D7719 llvm-svn: 231230
2015-03-04 19:05:34 +08:00
; 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
[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 llvm-svn: 232802
2015-03-20 18:00:37 +08:00
; CHECK: callq a
; CHECK: callq a
; CHECK: callq a
Add a flag to experiment with outlining optional branches. In a CFG with the edges A->B->C and A->C, B is an optional branch. LLVM's default behavior is to lay the blocks out naturally, i.e. A, B, C, in order to improve code locality and fallthroughs. However, if a function contains many of those optional branches only a few of which are taken, this leads to a lot of unnecessary icache misses. Moving B out of line can work around this. Review: http://reviews.llvm.org/D7719 llvm-svn: 231230
2015-03-04 19:05:34 +08:00
; CHECK: callq b
; CHECK: callq c
; CHECK: callq d
[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 llvm-svn: 232802
2015-03-20 18:00:37 +08:00
; CHECK: callq e
; CHECK: callq f
Add a flag to experiment with outlining optional branches. In a CFG with the edges A->B->C and A->C, B is an optional branch. LLVM's default behavior is to lay the blocks out naturally, i.e. A, B, C, in order to improve code locality and fallthroughs. However, if a function contains many of those optional branches only a few of which are taken, this leads to a lot of unnecessary icache misses. Moving B out of line can work around this. Review: http://reviews.llvm.org/D7719 llvm-svn: 231230
2015-03-04 19:05:34 +08:00
;
; CHECK-OUTLINE-LABEL: foo:
; CHECK-OUTLINE: callq b
; CHECK-OUTLINE: callq c
; CHECK-OUTLINE: callq d
[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 llvm-svn: 232802
2015-03-20 18:00:37 +08:00
; CHECK-OUTLINE: callq e
; CHECK-OUTLINE: callq f
; CHECK-OUTLINE: callq a
; CHECK-OUTLINE: callq a
; CHECK-OUTLINE: callq a
Add a flag to experiment with outlining optional branches. In a CFG with the edges A->B->C and A->C, B is an optional branch. LLVM's default behavior is to lay the blocks out naturally, i.e. A, B, C, in order to improve code locality and fallthroughs. However, if a function contains many of those optional branches only a few of which are taken, this leads to a lot of unnecessary icache misses. Moving B out of line can work around this. Review: http://reviews.llvm.org/D7719 llvm-svn: 231230
2015-03-04 19:05:34 +08:00
; CHECK-OUTLINE: callq a
entry:
%cmp = icmp eq i32 %t1, 0
br i1 %cmp, label %if.then, label %if.end
if.then:
[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 llvm-svn: 232802
2015-03-20 18:00:37 +08:00
call void @a()
call void @a()
call void @a()
Add a flag to experiment with outlining optional branches. In a CFG with the edges A->B->C and A->C, B is an optional branch. LLVM's default behavior is to lay the blocks out naturally, i.e. A, B, C, in order to improve code locality and fallthroughs. However, if a function contains many of those optional branches only a few of which are taken, this leads to a lot of unnecessary icache misses. Moving B out of line can work around this. Review: http://reviews.llvm.org/D7719 llvm-svn: 231230
2015-03-04 19:05:34 +08:00
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()
[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 llvm-svn: 232802
2015-03-20 18:00:37 +08:00
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()
Add a flag to experiment with outlining optional branches. In a CFG with the edges A->B->C and A->C, B is an optional branch. LLVM's default behavior is to lay the blocks out naturally, i.e. A, B, C, in order to improve code locality and fallthroughs. However, if a function contains many of those optional branches only a few of which are taken, this leads to a lot of unnecessary icache misses. Moving B out of line can work around this. Review: http://reviews.llvm.org/D7719 llvm-svn: 231230
2015-03-04 19:05:34 +08:00
ret void
}
declare void @a()
declare void @b()
declare void @c()
declare void @d()
[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 llvm-svn: 232802
2015-03-20 18:00:37 +08:00
declare void @e()
declare void @f()
Add a flag to experiment with outlining optional branches. In a CFG with the edges A->B->C and A->C, B is an optional branch. LLVM's default behavior is to lay the blocks out naturally, i.e. A, B, C, in order to improve code locality and fallthroughs. However, if a function contains many of those optional branches only a few of which are taken, this leads to a lot of unnecessary icache misses. Moving B out of line can work around this. Review: http://reviews.llvm.org/D7719 llvm-svn: 231230
2015-03-04 19:05:34 +08:00
!1 = !{!"branch_weights", i32 64, i32 4}