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2be00d9e54
Current tail duplication integrated in bb layout is designed to increase the fallthrough from a BB's predecessor to its successor, but we have observed cases that duplication doesn't increase fallthrough, or it brings too much size overhead. To overcome these two issues in function canTailDuplicateUnplacedPreds I add two checks: make sure there is at least one duplication in current work set. the number of duplication should not exceed the number of successors. The modification in hasBetterLayoutPredecessor fixes a bug that potential predecessor must be at the bottom of a chain. Differential Revision: https://reviews.llvm.org/D64376
92 lines
1.8 KiB
LLVM
92 lines
1.8 KiB
LLVM
; RUN: llc -O2 < %s | FileCheck %s
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target triple = "powerpc64le-grtev4-linux-gnu"
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; No duplication of loop header into entry block.
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define void @no_duplicate1(i64 %a) {
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; CHECK-LABEL: no_duplicate1
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; CHECK: mr 30, 3
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; CHECK-NEXT: b .LBB0_2
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; CHECK: .LBB0_2:
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; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
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; CHECK-NEXT: cmpldi 30, 100
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; CHECK-NEXT: bne 0, .LBB0_1
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entry:
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br label %header
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header:
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%ind = phi i64 [%a, %entry], [%val3, %latch]
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%cond1 = icmp eq i64 %ind, 100
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br i1 %cond1, label %middle, label %latch
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middle:
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%condx = call i1 @foo()
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%val1 = xor i64 %ind, 2
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br label %latch
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latch:
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%val2 = phi i64 [%ind, %header], [%val1, %middle]
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%val3 = add i64 %val2, 1
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%cond2 = call i1 @foo()
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br i1 %cond2, label %end, label %header
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end:
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ret void
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}
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; No duplication of loop header into latches.
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define void @no_duplicate2(i64 %a) {
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; CHECK-LABEL: no_duplicate2
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; CHECK: mr 30, 3
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; CHECK-NEXT: b .LBB1_2
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; CHECK: .LBB1_2:
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; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
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; CHECK-NEXT: cmpldi 30, 100
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; CHECK-NEXT: bne 0, .LBB1_1
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; CHECK: %latch2
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; CHECK: b .LBB1_2
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; CHECK: %latch3
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; CHECK: b .LBB1_2
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entry:
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br label %header
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header:
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%ind = phi i64 [%a, %entry], [%val1, %latch1], [%val2, %latch2], [%val2, %latch3]
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%cond1 = icmp eq i64 %ind, 100
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br i1 %cond1, label %middle1, label %latch1
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latch1:
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%cond2 = call i1 @foo()
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%val1 = xor i64 %ind, 2
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br i1 %cond2, label %end, label %header
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middle1:
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%cond3 = call i1 @foo()
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br i1 %cond3, label %latch1, label %middle2
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middle2:
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%cond4 = call i1 @foo()
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%val2 = add i64 %ind, 1
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br i1 %cond4, label %latch2, label %latch3
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latch2:
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call void @a()
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br label %header
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latch3:
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call void @b()
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br label %header
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end:
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ret void
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}
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declare i1 @foo()
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declare void @a()
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declare void @b()
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