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An irreducible SCC is one which has multiple "header" blocks, i.e., blocks with control-flow edges incident from outside the SCC. This pass converts an irreducible SCC into a natural loop by introducing a single new header block and redirecting all the edges on the original headers to this new block. This is a useful workaround for a limitation in the structurizer which, which produces incorrect control flow in the presence of irreducible regions. The AMDGPU backend provides an option to enable this pass before the structurizer, which may eventually be enabled by default. Reviewed By: nhaehnle Differential Revision: https://reviews.llvm.org/D77198 This restores commit 2ada8e2525dd2653f30c8696a27162a3b1647d66. Originally reverted with commit 44e09b59b869a91bf47d76e8bc569d9ee91ad145.
44 lines
1.4 KiB
LLVM
44 lines
1.4 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -fix-irreducible -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 label [[IRR_GUARD:%.*]]
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; CHECK: A:
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; CHECK-NEXT: br label [[IRR_GUARD]]
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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 [[IRR_GUARD]], label [[NEWDEFAULT:%.*]]
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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 [[IRR_GUARD]], label [[NEWDEFAULT]]
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; CHECK: NewDefault:
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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: irr.guard:
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; CHECK-NEXT: [[GUARD_A:%.*]] = phi i1 [ true, [[LEAFBLOCK]] ], [ [[PREDENTRY:%.*]], [[ENTRY:%.*]] ], [ false, [[LEAFBLOCK1]] ], [ false, [[A:%.*]] ]
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; CHECK-NEXT: br i1 [[GUARD_A]], label [[A]], label [[B:%.*]]
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;
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entry:
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br i1 %PredEntry, label %A, label %B
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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 %exit [
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i32 0, label %A
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i32 1, label %B
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]
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exit:
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ret void
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}
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