test/Transforms/GVN/memdep-unknown-deadblocks.ll

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes='function(gvn)' -S | FileCheck -check-prefixes=CHECK-GVN %s

; Also do some runs using an GVN+O1 pipeline, using O1 to clean up after GVN.
; This is to easier see the semantic of the resulting IR and that it hopefully
; is the same as if only running O1 directly.
;
; RUN: opt < %s -passes='function(gvn),default<O1>' -S | FileCheck -check-prefixes=CHECK-GVN-O1 %s
; RUN: opt < %s -passes='default<O1>' -S | FileCheck -check-prefixes=CHECK-O1 %s

; This is a reproducer for the miscompile reported here:
;   https://github.com/llvm/llvm-project/issues/57025
;
; Explanation of the test case:
;  - Outer loop will do three iterations i:=0, i:=1 and i:=2
;  - When is i==0 the value 7 is stored to arr[0]
;  - When is i!=0 the value 42 is stored to arr[i]
;  - There is a nestled while loop reduced down to something just setting j:=i
;    and then exiting.
;  - In while.end arr[j] (i.e. the just stored to arr[i]) is loaded,
;    and the loaded value is passed to the verify function.
;  - There is a dead load of the not yet initialized arr[j+1] in the epilog
;    block. This might seem irrelevant, but is needed to reproduce the
;    miscompile.
;
; Expected semantic of the function is that verify() will be called three
; times, with the values 7, 42 and 42.

declare void @verify(i16)

define void @test(i16 %g) {
; CHECK-GVN-LABEL: @test(
; CHECK-GVN-NEXT:  entry:
; CHECK-GVN-NEXT:    [[ARR:%.*]] = alloca [4 x i16], align 1
; CHECK-GVN-NEXT:    br label [[FOR_BODY:%.*]]
; CHECK-GVN:       for.body:
; CHECK-GVN-NEXT:    [[I:%.*]] = phi i16 [ 0, [[ENTRY:%.*]] ], [ [[NEXT_I:%.*]], [[WHILE_END:%.*]] ]
; CHECK-GVN-NEXT:    [[CMP0:%.*]] = icmp eq i16 [[I]], 0
; CHECK-GVN-NEXT:    br i1 [[CMP0]], label [[STORE_IDX_0:%.*]], label [[STORE_IDX_I:%.*]]
; CHECK-GVN:       store.idx.0:
; CHECK-GVN-NEXT:    store i16 7, ptr [[ARR]], align 1
; CHECK-GVN-NEXT:    br label [[STORE_DONE:%.*]]
; CHECK-GVN:       store.idx.i:
; CHECK-GVN-NEXT:    [[ARR_I:%.*]] = getelementptr [4 x i16], ptr [[ARR]], i16 0, i16 [[I]]
; CHECK-GVN-NEXT:    store i16 42, ptr [[ARR_I]], align 1
; CHECK-GVN-NEXT:    br label [[STORE_DONE]]
; CHECK-GVN:       store.done:
; CHECK-GVN-NEXT:    br label [[WHILE_BODY:%.*]]
; CHECK-GVN:       while.body:
; CHECK-GVN-NEXT:    br i1 false, label [[WHILE_BODY_WHILE_BODY_CRIT_EDGE:%.*]], label [[WHILE_END]]
; CHECK-GVN:       while.body.while.body_crit_edge:
; CHECK-GVN-NEXT:    br label [[WHILE_BODY]]
; CHECK-GVN:       while.end:
; CHECK-GVN-NEXT:    [[ARR_J:%.*]] = getelementptr [4 x i16], ptr [[ARR]], i16 0, i16 [[I]]
; CHECK-GVN-NEXT:    [[VALUE:%.*]] = load i16, ptr [[ARR_J]], align 1
; CHECK-GVN-NEXT:    tail call void @verify(i16 [[VALUE]])
; CHECK-GVN-NEXT:    [[NEXT_I]] = add i16 [[I]], 1
; CHECK-GVN-NEXT:    [[ARR_NEXT_I:%.*]] = getelementptr [4 x i16], ptr [[ARR]], i16 0, i16 [[NEXT_I]]
; CHECK-GVN-NEXT:    [[CMP4:%.*]] = icmp slt i16 [[NEXT_I]], 3
; CHECK-GVN-NEXT:    br i1 [[CMP4]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK-GVN:       for.end:
; CHECK-GVN-NEXT:    ret void
;
; CHECK-GVN-O1-LABEL: @test(
; CHECK-GVN-O1-NEXT:  entry:
; CHECK-GVN-O1-NEXT:    tail call void @verify(i16 7)
; CHECK-GVN-O1-NEXT:    tail call void @verify(i16 42)
; CHECK-GVN-O1-NEXT:    tail call void @verify(i16 42)
; CHECK-GVN-O1-NEXT:    ret void
;
; CHECK-O1-LABEL: @test(
; CHECK-O1-NEXT:  entry:
; CHECK-O1-NEXT:    tail call void @verify(i16 7)
; CHECK-O1-NEXT:    tail call void @verify(i16 42)
; CHECK-O1-NEXT:    tail call void @verify(i16 42)
; CHECK-O1-NEXT:    ret void
;
entry:
  %arr = alloca [4 x i16], align 1
  br label %for.body

for.body:                                         ; preds = %epilog, %entry
  %i = phi i16 [ 0, %entry ], [ %next.i, %epilog ]
  %cmp0 = icmp eq i16 %i, 0
  br i1 %cmp0, label %store.idx.0, label %store.idx.i

store.idx.0:                                      ; preds = %for.body
  store i16 7, ptr %arr, align 1
  br label %store.done

store.idx.i:                                      ; preds = %for.body
  %arr.i = getelementptr [4 x i16], ptr %arr, i16 0, i16 %i
  store i16 42, ptr %arr.i, align 1
  br label %store.done

store.done:                                        ; preds = %store.idx.i, %store.idx.0
  br label %while.body

while.body:                                       ; preds = %while.body, %store.done
  %j = phi i16 [ %i, %store.done ], [ 0, %while.body ]
  ; Constant foldable conditional branch.
  ; Needed to reproduce the fault!
  br i1 false, label %while.body, label %while.end

while.end:                                        ; preds = %while.body
  %arr.j = getelementptr [4 x i16], ptr %arr, i16 0, i16 %j
  %value = load i16, ptr %arr.j, align 1
  tail call void @verify(i16 %value)
  br label %epilog

epilog:                                          ; preds = %while.end
  %next.i = add i16 %j, 1
  %arr.next.i = getelementptr [4 x i16], ptr %arr, i16 0, i16 %next.i
  ; A dead load.
  ;  Needed to reproduce the fault!
  %dead = load i16, ptr %arr.next.i, align 1
  %cmp4 = icmp slt i16 %next.i, 3
  br i1 %cmp4, label %for.body, label %for.end

for.end:                                          ; preds = %epilog
  ret void
}