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70b146b25e
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
78 lines
1.5 KiB
LLVM
78 lines
1.5 KiB
LLVM
; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux < %s | FileCheck %s -check-prefix=CHECK
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; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux -outline-optional-branches < %s | FileCheck %s -check-prefix=CHECK-OUTLINE
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define void @foo(i32 %t1, i32 %t2, i32 %t3) {
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; Test that we lift the call to 'c' up to immediately follow the call to 'b'
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; when we disable the cfg conflict check.
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;
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; CHECK-LABEL: foo:
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; CHECK: callq a
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; CHECK: callq a
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; CHECK: callq a
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; CHECK: callq a
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; CHECK: callq b
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; CHECK: callq c
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; CHECK: callq d
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; CHECK: callq e
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; CHECK: callq f
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;
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; CHECK-OUTLINE-LABEL: foo:
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; CHECK-OUTLINE: callq b
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; CHECK-OUTLINE: callq c
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; CHECK-OUTLINE: callq d
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; CHECK-OUTLINE: callq e
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; CHECK-OUTLINE: callq f
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; CHECK-OUTLINE: callq a
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; CHECK-OUTLINE: callq a
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; CHECK-OUTLINE: callq a
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; CHECK-OUTLINE: callq a
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entry:
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%cmp = icmp eq i32 %t1, 0
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br i1 %cmp, label %if.then, label %if.end
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if.then:
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call void @a()
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call void @a()
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call void @a()
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call void @a()
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br label %if.end
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if.end:
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call void @b()
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br label %hotbranch
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hotbranch:
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%cmp2 = icmp eq i32 %t2, 0
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br i1 %cmp2, label %if.then2, label %if.end2, !prof !1
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if.then2:
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call void @c()
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br label %if.end2
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if.end2:
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call void @d()
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br label %shortbranch
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shortbranch:
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%cmp3 = icmp eq i32 %t3, 0
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br i1 %cmp3, label %if.then3, label %if.end3
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if.then3:
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call void @e()
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br label %if.end3
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if.end3:
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call void @f()
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ret void
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}
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declare void @a()
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declare void @b()
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declare void @c()
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declare void @d()
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declare void @e()
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declare void @f()
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!1 = !{!"branch_weights", i32 64, i32 4}
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