3cbbded68c
For each natural loop with multiple exit blocks, this pass creates a new block N such that all exiting blocks now branch to N, and then control flow is redistributed to all the original exit blocks. The bulk of the tranformation is a new function introduced in BasicBlockUtils that an redirect control flow from a set of incoming blocks to a set of outgoing blocks via a common "hub". This is a useful workaround for a limitation in the structurizer which incorrectly orders blocks when processing a nest of loops. This pass bypasses that issue by ensuring that each natural loop is recognized as a separate region. Since the structurizer is a region pass, it no longer sees a nest of loops in a single region, and instead processes each "level" in the nesting as a separate region. The AMDGPU backend provides a new option to enable this pass before the structurizer, which may eventually be enabled by default. Reviewers: madhur13490, arsenm, nhaehnle Reviewed By: nhaehnle Differential Revision: https://reviews.llvm.org/D75865
69 lines
1.8 KiB
LLVM
69 lines
1.8 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -unify-loop-exits -S | FileCheck %s
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define void @loop_1(i32 %Value, i1 %PredEntry, i1 %PredD) {
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; CHECK-LABEL: @loop_1(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br i1 [[PREDENTRY:%.*]], label [[A:%.*]], label [[G:%.*]]
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; CHECK: A:
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; CHECK-NEXT: br label [[B:%.*]]
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; CHECK: B:
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; CHECK-NEXT: br label [[NODEBLOCK:%.*]]
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; CHECK: NodeBlock:
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; CHECK-NEXT: [[PIVOT:%.*]] = icmp slt i32 [[VALUE:%.*]], 1
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; CHECK-NEXT: br i1 [[PIVOT]], label [[LEAFBLOCK:%.*]], label [[LEAFBLOCK1:%.*]]
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; CHECK: LeafBlock1:
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; CHECK-NEXT: [[SWITCHLEAF2:%.*]] = icmp eq i32 [[VALUE]], 1
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; CHECK-NEXT: br i1 [[SWITCHLEAF2]], label [[D:%.*]], label [[LOOP_EXIT_GUARD:%.*]]
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; CHECK: LeafBlock:
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; CHECK-NEXT: [[SWITCHLEAF:%.*]] = icmp eq i32 [[VALUE]], 0
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; CHECK-NEXT: br i1 [[SWITCHLEAF]], label [[C:%.*]], label [[LOOP_EXIT_GUARD]]
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; CHECK: C:
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; CHECK-NEXT: br label [[D]]
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; CHECK: D:
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; CHECK-NEXT: br i1 [[PREDD:%.*]], label [[A]], label [[LOOP_EXIT_GUARD]]
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; CHECK: NewDefault:
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; CHECK-NEXT: br label [[X:%.*]]
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; CHECK: X:
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; CHECK-NEXT: br label [[EXIT:%.*]]
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; CHECK: Y:
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; CHECK-NEXT: br label [[EXIT]]
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; CHECK: G:
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; CHECK-NEXT: br label [[EXIT]]
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; CHECK: exit:
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; CHECK-NEXT: ret void
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; CHECK: loop.exit.guard:
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; CHECK-NEXT: [[GUARD_NEWDEFAULT:%.*]] = phi i1 [ true, [[LEAFBLOCK1]] ], [ true, [[LEAFBLOCK]] ], [ false, [[D]] ]
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; CHECK-NEXT: br i1 [[GUARD_NEWDEFAULT]], label [[NEWDEFAULT:%.*]], label [[Y:%.*]]
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;
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entry:
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br i1 %PredEntry, label %A, label %G
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A:
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br label %B
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B:
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switch i32 %Value, label %X [
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i32 0, label %C
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i32 1, label %D
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]
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C:
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br label %D
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D:
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br i1 %PredD, label %A, label %Y
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X:
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br label %exit
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Y:
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br label %exit
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G:
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br label %exit
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exit:
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ret void
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}
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