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af1f058dcb
Current tail duplication embedded in MBP duplicates a BB into all or none of its predecessors without too much cost analysis. So sometimes it is duplicated into cold predecessors, and in other cases it may miss the duplication into hot predecessors. This patch improves tail duplication in 3 aspects: A successor can be duplicated into part of its predecessors. A more fine-grained benefit analysis, combined with 1, now a successor is duplicated into hot predecessors only. If a successor can't be duplicated into one predecessor, it doesn't impact the duplication into other predecessors. Differential Revision: https://reviews.llvm.org/D73387
188 lines
3.4 KiB
LLVM
188 lines
3.4 KiB
LLVM
; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
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@gvar = external global i32
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; dupbb has two predecessors, p1 and p2. p1 is hot, p2 is cold. So dupbb
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; should be placed after p1, and not duplicated into p2.
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;
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; CHECK-LABEL: test1
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; CHECK: %p1
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; CHECK: .LBB0_4: # %dupbb
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; CHECK: %p2
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; CHECK: jmp .LBB0_4
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define void @test1(i32* %p) !prof !1 {
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entry:
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br label %header
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header:
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%call = call zeroext i1 @a()
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br i1 %call, label %p1, label %p2, !prof !2
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p1:
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call void @b()
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br label %dupbb
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p2:
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call void @c()
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br label %dupbb
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dupbb:
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%cond = icmp eq i32* @gvar, %p
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br i1 %cond, label %header, label %latch, !prof !3
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latch:
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%call3 = call zeroext i1 @a()
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br i1 %call3, label %header, label %end, !prof !2
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end:
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ret void
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}
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; dupbb has four predecessors p1, p2, p3 and p4. p1 and p2 are hot, p3 and p4
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; are cold. So dupbb should be placed after p1, duplicated into p2. p3 and p4
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; should jump to dupbb.
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;
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; CHECK-LABEL: test2
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; CHECK: %p1
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; CHECK: .LBB1_8: # %dupbb
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;
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; CHECK: %p2
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; CHECK: callq c
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; CHECK-NEXT: cmpq
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; CHECK-NEXT: je
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; CHECK-NEXT: jmp
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;
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; CHECK: %p3
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; CHECK: jmp .LBB1_8
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; CHECK: %p4
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; CHECK: jmp .LBB1_8
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define void @test2(i32* %p) !prof !1 {
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entry:
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br label %header
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header:
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%call = call zeroext i1 @a()
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br i1 %call, label %bb1, label %bb2, !prof !2
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bb1:
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%call1 = call zeroext i1 @a()
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br i1 %call1, label %p1, label %p2, !prof !4
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bb2:
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%call2 = call zeroext i1 @a()
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br i1 %call2, label %p3, label %p4, !prof !4
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p1:
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call void @b()
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br label %dupbb
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p2:
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call void @c()
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br label %dupbb
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p3:
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call void @d()
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br label %dupbb
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p4:
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call void @e()
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br label %dupbb
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dupbb:
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%cond = icmp eq i32* @gvar, %p
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br i1 %cond, label %bb3, label %bb4, !prof !4
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bb3:
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call void @b()
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br label %bb4
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bb4:
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%call4 = call zeroext i1 @a()
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br i1 %call4, label %header, label %latch, !prof !3
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latch:
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%call3 = call zeroext i1 @a()
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br i1 %call3, label %header, label %end, !prof !2
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end:
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ret void
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}
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; dupbb has three predecessors p1, p2 and p3. p3 has two successors, so dupbb
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; can't be duplicated into p3, but it should not block it to be duplicated into
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; other predecessors.
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;
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; CHECK-LABEL: test3
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; CHECK: %p1
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; CHECK: .LBB2_6: # %dupbb
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;
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; CHECK: %p2
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; CHECK: callq c
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; CHECK: cmpq
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; CHECK-NEXT: je
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; CHECK-NEXT: jmp
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;
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; CHECK: %p3
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; CHECK: jne .LBB2_6
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define void @test3(i32* %p) !prof !1 {
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entry:
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br label %header
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header:
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%call = call zeroext i1 @a()
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br i1 %call, label %bb1, label %p3, !prof !2
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bb1:
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%call1 = call zeroext i1 @a()
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br i1 %call1, label %p1, label %p2, !prof !4
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p1:
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call void @b()
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br label %dupbb
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p2:
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call void @c()
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br label %dupbb
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p3:
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%call2 = call zeroext i1 @a()
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br i1 %call2, label %dupbb, label %bb4, !prof !4
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dupbb:
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%cond = icmp eq i32* @gvar, %p
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br i1 %cond, label %bb3, label %bb4, !prof !4
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bb3:
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call void @b()
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br label %bb4
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bb4:
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%call4 = call zeroext i1 @a()
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br i1 %call4, label %header, label %latch, !prof !3
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latch:
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%call3 = call zeroext i1 @a()
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br i1 %call3, label %header, label %end, !prof !2
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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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!1 = !{!"function_entry_count", i64 1000}
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!2 = !{!"branch_weights", i32 100, i32 1}
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!3 = !{!"branch_weights", i32 1, i32 100}
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!4 = !{!"branch_weights", i32 60, i32 40}
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