llvm/test/Transforms/IndVarSimplify/exit-value-guarded-positive-stride.ll

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -passes=indvars -S < %s | FileCheck %s
;
; The loop is not mustprogress and the stride is symbolic, so on its own SCEV
; cannot bound the trip count (a zero stride would loop forever) and
; IndVarSimplify leaves the loop intact. The dominating guard proves %s > 0,
; which makes the exit value computable and rewritten to a closed form.

define i32 @exit_value_guarded_positive_stride(i32 %s, i32 %n) {
; CHECK-LABEL: @exit_value_guarded_positive_stride(
; CHECK-NEXT:  entry:
; CHECK-NEXT:    [[G:%.*]] = icmp sgt i32 [[S:%.*]], 0
; CHECK-NEXT:    br i1 [[G]], label [[PH:%.*]], label [[BAIL:%.*]]
; CHECK:       bail:
; CHECK-NEXT:    ret i32 -1
; CHECK:       ph:
; CHECK-NEXT:    br label [[LOOP:%.*]]
; CHECK:       loop:
; CHECK-NEXT:    br i1 false, label [[LOOP]], label [[EXIT:%.*]]
; CHECK:       exit:
; CHECK-NEXT:    [[SMAX:%.*]] = call i32 @llvm.smax.i32(i32 [[N:%.*]], i32 [[S]])
; CHECK-NEXT:    [[TMP0:%.*]] = sub i32 [[SMAX]], [[S]]
; CHECK-NEXT:    [[UMIN:%.*]] = call i32 @llvm.umin.i32(i32 [[TMP0]], i32 1)
; CHECK-NEXT:    [[TMP1:%.*]] = sub i32 [[TMP0]], [[UMIN]]
; CHECK-NEXT:    [[UMAX:%.*]] = call i32 @llvm.umax.i32(i32 [[S]], i32 1)
; CHECK-NEXT:    [[TMP2:%.*]] = udiv i32 [[TMP1]], [[UMAX]]
; CHECK-NEXT:    [[TMP3:%.*]] = add i32 [[UMIN]], [[TMP2]]
; CHECK-NEXT:    [[TMP4:%.*]] = add i32 [[TMP3]], 1
; CHECK-NEXT:    ret i32 [[TMP4]]
;
entry:
  %g = icmp sgt i32 %s, 0
  br i1 %g, label %ph, label %bail

bail:
  ret i32 -1

ph:
  br label %loop

loop:
  %i = phi i32 [ 0, %ph ], [ %i.next, %loop ]
  %c = phi i32 [ 0, %ph ], [ %c.next, %loop ]
  %c.next = add i32 %c, 1
  %i.next = add nsw i32 %i, %s
  %cmp = icmp slt i32 %i.next, %n
  br i1 %cmp, label %loop, label %exit

exit:
  %lcssa = phi i32 [ %c.next, %loop ]
  ret i32 %lcssa
}