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llvm-6502/test/CodeGen/X86/pr2659.ll
Andrew Trick 12f0dc6bb5 In the pre-RA scheduler, maintain cmp+br proximity.
This is done by pushing physical register definitions close to their
use, which happens to handle flag definitions if they're not glued to
the branch. This seems to be generally a good thing though, so I
didn't need to add a target hook yet.

The primary motivation is to generate code closer to what people
expect and rule out missed opportunity from enabling macro-op
fusion. As a side benefit, we get several 2-5% gains on x86
benchmarks. There is one regression:
SingleSource/Benchmarks/Shootout/lists slows down be -10%. But this is
an independent scheduler bug that will be tracked separately.
See rdar://problem/9283108.

Incidentally, pre-RA scheduling is only half the solution. Fixing the
later passes is tracked by:
<rdar://problem/8932804> [pre-RA-sched] on x86, attempt to schedule CMP/TEST adjacent with condition jump

Fixes:
<rdar://problem/9262453> Scheduler unnecessary break of cmp/jump fusion


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129508 91177308-0d34-0410-b5e6-96231b3b80d8
2011-04-14 05:15:06 +00:00

42 lines
1.7 KiB
LLVM

; RUN: llc < %s -march=x86 -mtriple=i686-apple-darwin9.4.0 | grep movl | count 4
; RUN: llc < %s -march=x86 -mtriple=i686-apple-darwin9.4.0 | FileCheck %s
; PR2659
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i686-apple-darwin9.4.0"
define i32 @binomial(i32 %n, i32 %k) nounwind {
entry:
%cmp = icmp ugt i32 %k, %n ; <i1> [#uses=1]
br i1 %cmp, label %ifthen, label %forcond.preheader
forcond.preheader: ; preds = %entry
%cmp44 = icmp eq i32 %k, 0 ; <i1> [#uses=1]
br i1 %cmp44, label %afterfor, label %forbody
; CHECK: %forcond.preheader
; CHECK: movl $1
; CHECK-NOT: xorl
; CHECK-NOT: movl
; CHECK-NOT: LBB
; CHECK: je
ifthen: ; preds = %entry
ret i32 0
forbody: ; preds = %forbody, %forcond.preheader
%indvar = phi i32 [ 0, %forcond.preheader ], [ %divisor.02, %forbody ] ; <i32> [#uses=3]
%accumulator.01 = phi i32 [ 1, %forcond.preheader ], [ %div, %forbody ] ; <i32> [#uses=1]
%divisor.02 = add i32 %indvar, 1 ; <i32> [#uses=2]
%n.addr.03 = sub i32 %n, %indvar ; <i32> [#uses=1]
%mul = mul i32 %n.addr.03, %accumulator.01 ; <i32> [#uses=1]
%div = udiv i32 %mul, %divisor.02 ; <i32> [#uses=2]
%inc = add i32 %indvar, 2 ; <i32> [#uses=1]
%cmp4 = icmp ugt i32 %inc, %k ; <i1> [#uses=1]
br i1 %cmp4, label %afterfor, label %forbody
afterfor: ; preds = %forbody, %forcond.preheader
%accumulator.0.lcssa = phi i32 [ 1, %forcond.preheader ], [ %div, %forbody ] ; <i32> [#uses=1]
ret i32 %accumulator.0.lcssa
}