d2210af332
Current findBestLoopTop can find and move one kind of block to top, a latch block has one successor. Another common case is:
* a latch block
* it has two successors, one is loop header, another is exit
* it has more than one predecessors
If it is below one of its predecessors P, only P can fall through to it, all other predecessors need a jump to it, and another conditional jump to loop header. If it is moved before loop header, all its predecessors jump to it, then fall through to loop header. So all its predecessors except P can reduce one taken branch.
Differential Revision: https://reviews.llvm.org/D43256
llvm-svn: 363471
123 lines
2.2 KiB
LLVM
123 lines
2.2 KiB
LLVM
; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux < %s | FileCheck %s
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; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux -precise-rotation-cost < %s | FileCheck %s -check-prefix=CHECK-PROFILE
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define void @foo() {
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; Test a nested loop case when profile data is not available.
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;
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; CHECK-LABEL: foo:
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; CHECK: callq g
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; CHECK: callq h
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; CHECK: callq b
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; CHECK: callq e
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; CHECK: callq f
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; CHECK: callq c
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; CHECK: callq d
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entry:
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br label %header
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header:
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call void @b()
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%call = call zeroext i1 @a()
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br i1 %call, label %if.then, label %if.else, !prof !2
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if.then:
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br label %header2
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header2:
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call void @c()
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%call1 = call zeroext i1 @a()
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br i1 %call1, label %if.then2, label %if.else2, !prof !2
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if.then2:
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call void @d()
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br label %if.end2
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if.else2:
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call void @e()
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br label %if.end2
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if.end2:
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call void @f()
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%call2 = call zeroext i1 @a()
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br i1 %call2, label %header2, label %if.end
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if.else:
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call void @g()
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br label %if.end
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if.end:
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call void @h()
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%call3 = call zeroext i1 @a()
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br i1 %call3, label %header, label %end
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end:
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ret void
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}
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define void @bar() !prof !1 {
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; Test a nested loop case when profile data is available.
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;
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; CHECK-PROFILE-LABEL: bar:
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; CHECK-PROFILE: callq h
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; CHECK-PROFILE: callq b
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; CHECK-PROFILE: callq g
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; CHECK-PROFILE: callq e
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; CHECK-PROFILE: callq f
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; CHECK-PROFILE: callq c
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; CHECK-PROFILE: callq d
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entry:
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br label %header
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header:
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call void @b()
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%call = call zeroext i1 @a()
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br i1 %call, label %if.then, label %if.else, !prof !2
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if.then:
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br label %header2
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header2:
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call void @c()
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%call1 = call zeroext i1 @a()
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br i1 %call1, label %if.then2, label %if.else2, !prof !2
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if.then2:
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call void @d()
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br label %if.end2
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if.else2:
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call void @e()
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br label %if.end2
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if.end2:
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call void @f()
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%call2 = call zeroext i1 @a()
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br i1 %call2, label %header2, label %if.end
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if.else:
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call void @g()
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br label %if.end
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if.end:
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call void @h()
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%call3 = call zeroext i1 @a()
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br i1 %call3, label %header, label %end
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end:
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ret void
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}
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declare zeroext i1 @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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declare void @g()
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declare void @h()
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!1 = !{!"function_entry_count", i64 1}
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!2 = !{!"branch_weights", i32 16, i32 16}
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