llvm-6502/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll
Andrew Trick c9b1e25493 Enable the new LoopInfo algorithm by default.
The primary advantage is that loop optimizations will be applied in a
stable order. This helps debugging and unit test creation. It is also
a better overall implementation without pathologically bad performance
on deep functions.

On large functions (llvm-stress --size=200000 | opt -loops)
Before: 0.1263s
After:  0.0225s

On deep functions (after tweaking llvm-stress, thanks Nadav):
Before: 0.2281s
After:  0.0227s

See r158790 for more comments.

The loop tree is now consistently generated in forward order, but loop
passes are applied in reverse order over the program. If we have a
loop optimization that prefers forward order, that can easily be
achieved by adding a different type of LoopPassManager.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159183 91177308-0d34-0410-b5e6-96231b3b80d8
2012-06-26 04:11:38 +00:00

85 lines
2.8 KiB
LLVM

; RUN: opt -loop-unswitch -loop-unswitch-threshold 13 -disable-output -stats -info-output-file - < %s | FileCheck --check-prefix=STATS %s
; RUN: opt -S -loop-unswitch -loop-unswitch-threshold 13 -verify-loop-info -verify-dom-info %s | FileCheck %s
; STATS: 1 loop-simplify - Number of pre-header or exit blocks inserted
; STATS: 1 loop-unswitch - Number of switches unswitched
; ModuleID = '../llvm/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll'
; CHECK: %1 = icmp eq i32 %c, 1
; CHECK-NEXT: br i1 %1, label %.split.us, label %..split_crit_edge
; CHECK: ..split_crit_edge: ; preds = %0
; CHECK-NEXT: br label %.split
; CHECK: .split.us: ; preds = %0
; CHECK-NEXT: br label %loop_begin.us
; CHECK: loop_begin.us: ; preds = %loop_begin.backedge.us, %.split.us
; CHECK: switch i32 1, label %second_switch.us [
; CHECK-NEXT: i32 1, label %inc.us
; CHECK: second_switch.us: ; preds = %loop_begin.us
; CHECK-NEXT: switch i32 %d, label %default.us [
; CHECK-NEXT: i32 1, label %inc.us
; CHECK-NEXT: ]
; CHECK: inc.us: ; preds = %second_switch.us, %loop_begin.us
; CHECK-NEXT: call void @incf() noreturn nounwind
; CHECK-NEXT: br label %loop_begin.backedge.us
; CHECK: .split: ; preds = %..split_crit_edge
; CHECK-NEXT: br label %loop_begin
; CHECK: loop_begin: ; preds = %loop_begin.backedge, %.split
; CHECK: switch i32 %c, label %second_switch [
; CHECK-NEXT: i32 1, label %loop_begin.inc_crit_edge
; CHECK-NEXT: ]
; CHECK: loop_begin.inc_crit_edge: ; preds = %loop_begin
; CHECK-NEXT: br i1 true, label %us-unreachable, label %inc
; CHECK: second_switch: ; preds = %loop_begin
; CHECK-NEXT: switch i32 %d, label %default [
; CHECK-NEXT: i32 1, label %inc
; CHECK-NEXT: ]
; CHECK: inc: ; preds = %loop_begin.inc_crit_edge, %second_switch
; CHECK-NEXT: call void @incf() noreturn nounwind
; CHECK-NEXT: br label %loop_begin.backedge
define i32 @test(i32* %var) {
%mem = alloca i32
store i32 2, i32* %mem
%c = load i32* %mem
%d = load i32* %mem
br label %loop_begin
loop_begin:
%var_val = load i32* %var
switch i32 %c, label %second_switch [
i32 1, label %inc
]
second_switch:
switch i32 %d, label %default [
i32 1, label %inc
]
inc:
call void @incf() noreturn nounwind
br label %loop_begin
default:
br label %loop_begin
loop_exit:
ret i32 0
}
declare void @incf() noreturn
declare void @decf() noreturn