1e01f95057
The NewDefault was used to simplify the updating of PHI nodes, but it
causes some inefficiency for target that will run structurizer later. For
example, for a simple two-case switch, the extra NewDefault is causing
unstructured CFG like:
O
/ \
O O
/ \ / \
C1 ND C2
\ | /
\ | /
D
The change is to avoid the ND(NewDefault) block, that is we will get a
structured CFG for above example like:
O
/ \
/ \
O O
/ \ / \
C1 \ / C2
\-> D <-/
The IR change introduced by this patch should be trivial to other targets,
so I am doing this unconditionally.
Fall-through among the cases will also cause unstructured CFG, but it need
more work and will be addressed in a separate change.
Reviewed by: arsenm
Differential Revision: https://reviews.llvm.org/D123607
106 lines
3.6 KiB
LLVM
106 lines
3.6 KiB
LLVM
; RUN: opt < %s -lowerswitch -S | FileCheck %s
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; RUN: opt < %s -passes=lowerswitch -S | FileCheck %s
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; We have switch on input.
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; On output we should got binary comparison tree. Check that all is fine.
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;CHECK: entry:
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;CHECK-NEXT: br label %NodeBlock19
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;CHECK: NodeBlock19: ; preds = %entry
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;CHECK-NEXT: %Pivot20 = icmp slt i32 %tmp158, 10
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;CHECK-NEXT: br i1 %Pivot20, label %NodeBlock5, label %NodeBlock17
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;CHECK: NodeBlock17: ; preds = %NodeBlock19
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;CHECK-NEXT: %Pivot18 = icmp slt i32 %tmp158, 13
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;CHECK-NEXT: br i1 %Pivot18, label %NodeBlock9, label %NodeBlock15
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;CHECK: NodeBlock15: ; preds = %NodeBlock17
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;CHECK-NEXT: %Pivot16 = icmp slt i32 %tmp158, 14
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;CHECK-NEXT: br i1 %Pivot16, label %bb330, label %NodeBlock13
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;CHECK: NodeBlock13: ; preds = %NodeBlock15
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;CHECK-NEXT: %Pivot14 = icmp slt i32 %tmp158, 15
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;CHECK-NEXT: br i1 %Pivot14, label %bb332, label %LeafBlock11
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;CHECK: LeafBlock11: ; preds = %NodeBlock13
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;CHECK-NEXT: %SwitchLeaf12 = icmp eq i32 %tmp158, 15
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;CHECK-NEXT: br i1 %SwitchLeaf12, label %bb334, label %bb336
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;CHECK: NodeBlock9: ; preds = %NodeBlock17
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;CHECK-NEXT: %Pivot10 = icmp slt i32 %tmp158, 11
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;CHECK-NEXT: br i1 %Pivot10, label %bb324, label %NodeBlock7
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;CHECK: NodeBlock7: ; preds = %NodeBlock9
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;CHECK-NEXT: %Pivot8 = icmp slt i32 %tmp158, 12
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;CHECK-NEXT: br i1 %Pivot8, label %bb326, label %bb328
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;CHECK: NodeBlock5: ; preds = %NodeBlock19
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;CHECK-NEXT: %Pivot6 = icmp slt i32 %tmp158, 7
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;CHECK-NEXT: br i1 %Pivot6, label %NodeBlock, label %NodeBlock3
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;CHECK: NodeBlock3: ; preds = %NodeBlock5
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;CHECK-NEXT: %Pivot4 = icmp slt i32 %tmp158, 8
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;CHECK-NEXT: br i1 %Pivot4, label %bb, label %NodeBlock1
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;CHECK: NodeBlock1: ; preds = %NodeBlock3
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;CHECK-NEXT: %Pivot2 = icmp slt i32 %tmp158, 9
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;CHECK-NEXT: br i1 %Pivot2, label %bb338, label %bb322
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;CHECK: NodeBlock: ; preds = %NodeBlock5
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;CHECK-NEXT: %Pivot = icmp slt i32 %tmp158, 0
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;CHECK-NEXT: br i1 %Pivot, label %LeafBlock, label %bb338
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;CHECK: LeafBlock: ; preds = %NodeBlock
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;CHECK-NEXT: %tmp158.off = add i32 %tmp158, 6
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;CHECK-NEXT: %SwitchLeaf = icmp ule i32 %tmp158.off, 4
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;CHECK-NEXT: br i1 %SwitchLeaf, label %bb338, label %bb336
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define i32 @main(i32 %tmp158) {
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entry:
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switch i32 %tmp158, label %bb336 [
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i32 -2, label %bb338
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i32 -3, label %bb338
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i32 -4, label %bb338
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i32 -5, label %bb338
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i32 -6, label %bb338
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i32 0, label %bb338
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i32 1, label %bb338
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i32 2, label %bb338
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i32 3, label %bb338
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i32 4, label %bb338
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i32 5, label %bb338
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i32 6, label %bb338
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i32 7, label %bb
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i32 8, label %bb338
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i32 9, label %bb322
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i32 10, label %bb324
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i32 11, label %bb326
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i32 12, label %bb328
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i32 13, label %bb330
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i32 14, label %bb332
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i32 15, label %bb334
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]
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bb:
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ret i32 2
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bb322:
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ret i32 3
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bb324:
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ret i32 4
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bb326:
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ret i32 5
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bb328:
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ret i32 6
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bb330:
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ret i32 7
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bb332:
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ret i32 8
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bb334:
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ret i32 9
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bb336:
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ret i32 10
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bb338:
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ret i32 11
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}
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