llvm-project/llvm/test/Transforms/JumpThreading/header-succ.ll

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -jump-threading < %s | FileCheck %s

; Check that the heuristic for avoiding accidental introduction of irreducible
; loops doesn't also prevent us from threading simple constructs where this
; isn't a problem.

declare void @opaque_body()

define void @jump_threading_loopheader() {
; CHECK-LABEL: @jump_threading_loopheader(
; CHECK-NEXT:  top:
; CHECK-NEXT:    br label [[ENTRY:%.*]]
; CHECK:       entry:
; CHECK-NEXT:    [[IND:%.*]] = phi i32 [ 0, [[TOP:%.*]] ], [ [[NEXTIND:%.*]], [[LATCH:%.*]] ]
; CHECK-NEXT:    [[NEXTIND]] = add i32 [[IND]], 1
; CHECK-NEXT:    [[CMP:%.*]] = icmp ule i32 [[IND]], 10
; CHECK-NEXT:    br i1 [[CMP]], label [[LATCH]], label [[EXIT:%.*]]
; CHECK:       latch:
; CHECK-NEXT:    call void @opaque_body()
; CHECK-NEXT:    br label [[ENTRY]]
; CHECK:       exit:
; CHECK-NEXT:    ret void
;
top:
  br label %entry

entry:
  %ind = phi i32 [0, %top], [%nextind, %latch]
  %nextind = add i32 %ind, 1
  %cmp = icmp ule i32 %ind, 10
  br i1 %cmp, label %body, label %latch

body:
  call void @opaque_body()
  br label %latch

latch:
  %cond = phi i2 [1, %entry], [2, %body]
  switch i2 %cond, label %unreach [
  i2 2, label %entry
  i2 1, label %exit
  ]

unreach:
  unreachable

exit:
  ret void
}

; We also need to check the opposite order of the branches, in the switch
; instruction because jump-threading relies on that to decide which edge to
; try to thread first.
define void @jump_threading_loopheader2() {
; CHECK-LABEL: @jump_threading_loopheader2(
; CHECK-NEXT:  top:
; CHECK-NEXT:    br label [[ENTRY:%.*]]
; CHECK:       entry:
; CHECK-NEXT:    [[IND:%.*]] = phi i32 [ 0, [[TOP:%.*]] ], [ [[NEXTIND:%.*]], [[LATCH:%.*]] ]
; CHECK-NEXT:    [[NEXTIND]] = add i32 [[IND]], 1
; CHECK-NEXT:    [[CMP:%.*]] = icmp ule i32 [[IND]], 10
; CHECK-NEXT:    br i1 [[CMP]], label [[EXIT:%.*]], label [[LATCH]]
; CHECK:       latch:
; CHECK-NEXT:    br label [[ENTRY]]
; CHECK:       exit:
; CHECK-NEXT:    call void @opaque_body()
; CHECK-NEXT:    ret void
;
top:
  br label %entry

entry:
  %ind = phi i32 [0, %top], [%nextind, %latch]
  %nextind = add i32 %ind, 1
  %cmp = icmp ule i32 %ind, 10
  br i1 %cmp, label %body, label %latch

body:
  call void @opaque_body()
  br label %latch

latch:
  %cond = phi i2 [1, %entry], [2, %body]
  switch i2 %cond, label %unreach [
  i2 1, label %entry
  i2 2, label %exit
  ]

unreach:
  unreachable

exit:
  ret void
}

; Check if we can handle undef branch condition.
define void @jump_threading_loopheader3() {
; CHECK-LABEL: @jump_threading_loopheader3(
; CHECK-NEXT:  top:
; CHECK-NEXT:    br label [[ENTRY:%.*]]
; CHECK:       entry:
; CHECK-NEXT:    [[IND:%.*]] = phi i32 [ 0, [[TOP:%.*]] ], [ [[NEXTIND:%.*]], [[LATCH:%.*]] ]
; CHECK-NEXT:    [[NEXTIND]] = add i32 [[IND]], 1
; CHECK-NEXT:    [[CMP:%.*]] = icmp ule i32 [[IND]], 10
; CHECK-NEXT:    br i1 [[CMP]], label [[LATCH]], label [[EXIT:%.*]]
; CHECK:       latch:
; CHECK-NEXT:    call void @opaque_body()
; CHECK-NEXT:    br label [[ENTRY]]
; CHECK:       exit:
; CHECK-NEXT:    ret void
;
top:
  br label %entry

entry:
  %ind = phi i32 [0, %top], [%nextind, %latch]
  %nextind = add i32 %ind, 1
  %cmp = icmp ule i32 %ind, 10
  br i1 %cmp, label %body, label %latch

body:
  call void @opaque_body()
  br label %latch

latch:
  %phi = phi i32 [undef, %entry], [0, %body]
  %cmp1 = icmp eq i32 %phi, 0
  br i1 %cmp1, label %entry, label %exit

exit:
  ret void
}