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llvm-mirror/test/Transforms/LoopUnroll/dce.ll
Philip Reames a4f9bca98e Do actual DCE in LoopUnroll (try 4)
Turns out simplifyLoopIVs sometimes returns a non-dead instruction in it's DeadInsts out param.  I had done a bit of NFC cleanup which was only NFC if simplifyLoopIVs obeyed it's documentation.  I'm simplfy dropping that part of the change.

Commit message from try 3:

Recommitting after fixing a bug found post commit. Amusingly, try 1 had been correct, and by reverting to incorporate last minute review feedback, I introduce the bug. Oops. :)

Original commit message:

The problem was that recursively deleting an instruction can delete instructions beyond the current iterator (via a dead phi), thus invalidating iteration. Test case added in LoopUnroll/dce.ll to cover this case.

LoopUnroll does a limited DCE pass after unrolling, but if you have a chain of dead instructions, it only deletes the last one. Improve the code to recursively delete all trivially dead instructions.

Differential Revision: https://reviews.llvm.org/D102511
2021-05-19 10:25:31 -07:00

61 lines
1.5 KiB
LLVM

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -loop-unroll -S < %s | FileCheck %s
; Can't recursively delete %c.addr.07 without deleting %conv1
; and thus invalidating iteration.
define void @PR50368(i32 %c, i64 %x) {
; CHECK-LABEL: @PR50368(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP_PEEL_BEGIN:%.*]]
; CHECK: loop.peel.begin:
; CHECK-NEXT: br label [[LOOP_PEEL:%.*]]
; CHECK: loop.peel:
; CHECK-NEXT: br i1 false, label [[EXIT:%.*]], label [[LOOP_PEEL_NEXT:%.*]]
; CHECK: loop.peel.next:
; CHECK-NEXT: br label [[LOOP_PEEL_NEXT1:%.*]]
; CHECK: loop.peel.next1:
; CHECK-NEXT: br label [[ENTRY_PEEL_NEWPH:%.*]]
; CHECK: entry.peel.newph:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: br i1 false, label [[EXIT_LOOPEXIT:%.*]], label [[LOOP]], !llvm.loop [[LOOP0:![0-9]+]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop
loop:
%0 = phi i64 [ 0, %loop ], [ %x, %entry ]
%c.addr.07 = phi i32 [ %conv1, %loop ], [ %c, %entry ]
%conv1 = trunc i64 undef to i32
br i1 false, label %exit, label %loop
exit:
ret void
}
define void @dead_chain(i64 %a) {
; CHECK-LABEL: @dead_chain(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: ret void
;
entry:
br label %loop
loop:
%conv1 = trunc i64 %a to i32
%and = and i32 %conv1, 15
%shl = shl i32 %and, 15
br i1 true, label %exit, label %loop
exit:
ret void
}