a4772cbaf0
This reverts commit 4e545bdb35.
The newly added test is the third infinite combine loop caused by
this change. In this case, it's a combination of the branch to
common dest and jump threading folds that keeps peeling off loop
iterations.
The core problem here is that we ideally would not thread over
loop backedges, both because it is potentially non-profitable
(it may break canonical loop structure) and because it may result
in these kinds of loops. Unfortunately, due to the lack of a
dominator tree in SimplifyCFG, there is no good way to prevent
this. While we have LoopHeaders, this is an optional structure and
we don't do a good job of keeping it up to date. It would be fine
for a profitability check, but is not suitable for a correctness
check.
So for now I'm just giving up here, as I don't see a good way to
robustly prevent infinite combine loops.
Fixes https://github.com/llvm/llvm-project/issues/56203.
423 lines
10 KiB
LLVM
423 lines
10 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -S -simplifycfg < %s | FileCheck %s
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declare void @foo()
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declare void @bar()
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declare void @use.i1(i1)
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declare void @use.i32(i32)
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define void @test_phi_simple(i1 %c) {
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; CHECK-LABEL: @test_phi_simple(
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; CHECK-NEXT: br i1 [[C:%.*]], label [[IF:%.*]], label [[ELSE:%.*]]
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; CHECK: if:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[JOIN2:%.*]]
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; CHECK: else:
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br label [[JOIN2]]
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; CHECK: join2:
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; CHECK-NEXT: ret void
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;
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br i1 %c, label %if, label %else
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if:
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call void @foo()
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br label %join
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else:
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call void @bar()
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br label %join
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join:
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%c2 = phi i1 [ true, %if ], [ false, %else ]
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br i1 %c2, label %if2, label %else2
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if2:
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call void @foo()
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br label %join2
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else2:
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call void @bar()
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br label %join2
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join2:
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ret void
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}
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define void @test_phi_extra_use(i1 %c) {
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; CHECK-LABEL: @test_phi_extra_use(
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; CHECK-NEXT: br i1 [[C:%.*]], label [[IF:%.*]], label [[ELSE:%.*]]
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; CHECK: if:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: call void @use.i1(i1 true)
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[JOIN2:%.*]]
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; CHECK: else:
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: call void @use.i1(i1 false)
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br label [[JOIN2]]
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; CHECK: join2:
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; CHECK-NEXT: ret void
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;
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br i1 %c, label %if, label %else
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if:
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call void @foo()
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br label %join
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else:
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call void @bar()
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br label %join
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join:
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%c2 = phi i1 [ true, %if ], [ false, %else ]
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call void @use.i1(i1 %c2)
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br i1 %c2, label %if2, label %else2
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if2:
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call void @foo()
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br label %join2
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else2:
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call void @bar()
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br label %join2
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join2:
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ret void
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}
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define void @test_phi_extra_use_different_block(i1 %c) {
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; CHECK-LABEL: @test_phi_extra_use_different_block(
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; CHECK-NEXT: br i1 [[C:%.*]], label [[IF:%.*]], label [[ELSE:%.*]]
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; CHECK: if:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[JOIN:%.*]]
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; CHECK: else:
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br label [[JOIN]]
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; CHECK: join:
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; CHECK-NEXT: [[C2:%.*]] = phi i1 [ true, [[IF]] ], [ false, [[ELSE]] ]
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; CHECK-NEXT: br i1 [[C2]], label [[IF2:%.*]], label [[ELSE2:%.*]]
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; CHECK: if2:
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; CHECK-NEXT: call void @use.i1(i1 [[C2]])
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[JOIN2:%.*]]
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; CHECK: else2:
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; CHECK-NEXT: call void @use.i1(i1 [[C2]])
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br label [[JOIN2]]
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; CHECK: join2:
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; CHECK-NEXT: ret void
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;
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br i1 %c, label %if, label %else
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if:
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call void @foo()
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br label %join
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else:
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call void @bar()
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br label %join
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join:
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%c2 = phi i1 [ true, %if ], [ false, %else ]
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br i1 %c2, label %if2, label %else2
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if2:
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call void @use.i1(i1 %c2)
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call void @foo()
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br label %join2
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else2:
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call void @use.i1(i1 %c2)
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call void @bar()
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br label %join2
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join2:
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ret void
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}
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define void @test_same_cond_simple(i1 %c) {
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; CHECK-LABEL: @test_same_cond_simple(
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; CHECK-NEXT: br i1 [[C:%.*]], label [[IF:%.*]], label [[ELSE:%.*]]
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; CHECK: if:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[JOIN:%.*]]
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; CHECK: else:
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br label [[JOIN]]
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; CHECK: join:
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; CHECK-NEXT: br i1 [[C]], label [[IF2:%.*]], label [[ELSE2:%.*]]
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; CHECK: if2:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[JOIN2:%.*]]
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; CHECK: else2:
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br label [[JOIN2]]
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; CHECK: join2:
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; CHECK-NEXT: ret void
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;
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br i1 %c, label %if, label %else
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if:
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call void @foo()
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br label %join
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else:
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call void @bar()
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br label %join
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join:
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br i1 %c, label %if2, label %else2
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if2:
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call void @foo()
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br label %join2
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else2:
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call void @bar()
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br label %join2
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join2:
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ret void
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}
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define void @test_same_cond_extra_use(i1 %c) {
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; CHECK-LABEL: @test_same_cond_extra_use(
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; CHECK-NEXT: br i1 [[C:%.*]], label [[IF:%.*]], label [[ELSE:%.*]]
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; CHECK: if:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[JOIN:%.*]]
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; CHECK: else:
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br label [[JOIN]]
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; CHECK: join:
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; CHECK-NEXT: call void @use.i1(i1 [[C]])
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; CHECK-NEXT: br i1 [[C]], label [[IF2:%.*]], label [[ELSE2:%.*]]
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; CHECK: if2:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[JOIN2:%.*]]
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; CHECK: else2:
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br label [[JOIN2]]
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; CHECK: join2:
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; CHECK-NEXT: ret void
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;
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br i1 %c, label %if, label %else
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if:
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call void @foo()
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br label %join
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else:
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call void @bar()
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br label %join
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join:
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call void @use.i1(i1 %c)
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br i1 %c, label %if2, label %else2
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if2:
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call void @foo()
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br label %join2
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else2:
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call void @bar()
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br label %join2
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join2:
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ret void
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}
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define void @test_same_cond_extra_use_different_block(i1 %c) {
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; CHECK-LABEL: @test_same_cond_extra_use_different_block(
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; CHECK-NEXT: br i1 [[C:%.*]], label [[IF:%.*]], label [[ELSE:%.*]]
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; CHECK: if:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[JOIN:%.*]]
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; CHECK: else:
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br label [[JOIN]]
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; CHECK: join:
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; CHECK-NEXT: br i1 [[C]], label [[IF2:%.*]], label [[ELSE2:%.*]]
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; CHECK: if2:
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; CHECK-NEXT: call void @use.i1(i1 [[C]])
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[JOIN2:%.*]]
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; CHECK: else2:
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; CHECK-NEXT: call void @use.i1(i1 [[C]])
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br label [[JOIN2]]
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; CHECK: join2:
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; CHECK-NEXT: ret void
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;
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br i1 %c, label %if, label %else
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if:
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call void @foo()
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br label %join
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else:
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call void @bar()
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br label %join
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join:
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br i1 %c, label %if2, label %else2
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if2:
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call void @use.i1(i1 %c)
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call void @foo()
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br label %join2
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else2:
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call void @use.i1(i1 %c)
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call void @bar()
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br label %join2
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join2:
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ret void
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}
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define void @test_multiple_threadable_preds_with_phi(i1 %cond1, i1 %cond2) {
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; CHECK-LABEL: @test_multiple_threadable_preds_with_phi(
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; CHECK-NEXT: br i1 [[COND1:%.*]], label [[IF1:%.*]], label [[IF2:%.*]]
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; CHECK: if1:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br i1 [[COND2:%.*]], label [[IF3_CRITEDGE:%.*]], label [[EXIT:%.*]]
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; CHECK: if2:
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: br i1 [[COND2]], label [[IF3_CRITEDGE]], label [[EXIT]]
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; CHECK: if3.critedge:
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; CHECK-NEXT: [[PHI_PH:%.*]] = phi i32 [ 2, [[IF2]] ], [ 1, [[IF1]] ]
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; CHECK-NEXT: call void @use.i32(i32 [[PHI_PH]])
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; CHECK-NEXT: call void @foo()
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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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;
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br i1 %cond1, label %if1, label %if2
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if1:
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call void @foo()
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br i1 %cond2, label %join, label %exit
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if2:
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call void @bar()
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br i1 %cond2, label %join, label %exit
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join:
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%phi = phi i32 [ 1, %if1 ], [ 2, %if2 ]
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call void @use.i32(i32 %phi)
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br i1 %cond2, label %if3, label %exit
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if3:
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call void @foo()
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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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; This test case used to infinite loop.
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define void @infloop(i1 %cmp.a, i1 %cmp.b, i1 %cmp.c) {
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; CHECK-LABEL: @infloop(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[WHILE_COND:%.*]]
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; CHECK: while.cond:
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; CHECK-NEXT: br i1 [[CMP_A:%.*]], label [[FOR:%.*]], label [[WHILE_BODY_THREAD:%.*]]
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; CHECK: for.body:
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; CHECK-NEXT: br i1 [[CMP_B:%.*]], label [[WHILE_BODY:%.*]], label [[FOR_BODY:%.*]]
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; CHECK: for:
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; CHECK-NEXT: tail call void @foo()
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; CHECK-NEXT: br label [[FOR_BODY]]
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; CHECK: while.body:
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; CHECK-NEXT: br i1 [[CMP_C:%.*]], label [[C_EXIT:%.*]], label [[LAND:%.*]]
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; CHECK: while.body.thread:
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; CHECK-NEXT: br i1 [[CMP_C]], label [[WHILE_COND]], label [[LAND]]
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; CHECK: land:
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; CHECK-NEXT: tail call void @bar()
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; CHECK-NEXT: br label [[WHILE_COND]]
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; CHECK: c.exit:
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; CHECK-NEXT: br i1 [[CMP_A]], label [[FOR_D:%.*]], label [[WHILE_BODY_THREAD]]
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; CHECK: for.d:
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; CHECK-NEXT: ret void
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;
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entry:
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br label %while.cond
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while.cond: ; preds = %land, %while.body.thread, %entry
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br i1 %cmp.a, label %for, label %while.body.thread
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for.body: ; preds = %for, %for.body
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br i1 %cmp.b, label %while.body, label %for.body
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for: ; preds = %while.cond
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tail call void @foo()
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br label %for.body
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while.body: ; preds = %for.body
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br i1 %cmp.c, label %c.exit, label %land
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while.body.thread: ; preds = %c.exit, %while.cond
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br i1 %cmp.c, label %while.cond, label %land
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land: ; preds = %while.body.thread, %while.body
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tail call void @bar()
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br label %while.cond
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c.exit: ; preds = %while.body
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br i1 %cmp.a, label %for.d, label %while.cond
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for.d: ; preds = %c.exit
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ret void
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}
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; A combination of "branch to common dest" and jump threading kept peeling
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; off loop iterations here.
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define void @infloop_pr56203(i1 %c1, i1 %c2) {
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; CHECK-LABEL: @infloop_pr56203(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br i1 [[C1:%.*]], label [[EXIT:%.*]], label [[IF:%.*]]
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; CHECK: if:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: [[C3:%.*]] = icmp eq i64 0, 0
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; CHECK-NEXT: [[OR_COND:%.*]] = or i1 [[C2:%.*]], [[C3]]
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; CHECK-NEXT: br i1 [[OR_COND]], label [[EXIT]], label [[LOOP_SPLIT:%.*]]
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; CHECK: loop:
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; CHECK-NEXT: [[C3_OLD:%.*]] = icmp eq i64 0, 0
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; CHECK-NEXT: br i1 [[C3_OLD]], label [[EXIT]], label [[LOOP_SPLIT]]
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; CHECK: loop.split:
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; CHECK-NEXT: br i1 [[C1]], label [[LOOP_LATCH:%.*]], label [[LOOP:%.*]]
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; CHECK: loop.latch:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label [[LOOP]]
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; CHECK: exit:
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; CHECK-NEXT: ret void
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;
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entry:
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br i1 %c1, label %exit, label %if
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if:
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call void @foo()
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br i1 %c2, label %exit, label %loop
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loop:
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%c3 = icmp eq i64 0, 0
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br i1 %c3, label %exit, label %loop.split
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loop.split:
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br i1 %c1, label %loop.latch, label %loop
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loop.latch:
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call void @foo()
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br label %loop
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exit:
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ret void
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}
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