471e856f49
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
51 lines
1.0 KiB
LLVM
51 lines
1.0 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) {
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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 b
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; CHECK: callq c
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; CHECK: callq d
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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 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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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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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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!1 = !{!"branch_weights", i32 64, i32 4}
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