[llvm-bugs] [Bug 34293] New: Optimizer fails to unroll the Coroutine-Loop.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=34293

            Bug ID: 34293
           Summary: Optimizer fails to unroll the Coroutine-Loop.
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Loop Optimizer
          Assignee: unassignedbugs at nondot.org
          Reporter: peetlugen19 at yandex.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 19033
  --> https://bugs.llvm.org/attachment.cgi?id=19033&action=edit
testcase

Test case: https://godbolt.org/g/esjnb2

I've also attached the test-case as an attachment.

LLVM-IR:

define void @printEquivalent()() local_unnamed_addr #0 !dbg !684 {
  %1 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([3 x i8],
[3 x i8]* @.str, i64 0, i64 0), i32 1), !dbg !685
  %2 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([3 x i8],
[3 x i8]* @.str, i64 0, i64 0), i32 3), !dbg !686
  ret void, !dbg !687
}

declare i32 @printf(i8* nocapture readonly, ...) local_unnamed_addr #1

define i32 @main() local_unnamed_addr #2 personality i8* bitcast (i32 (...)*
@__gxx_personality_v0 to i8*) !dbg !688 {
  br label %1, !dbg !693

; <label>:1:                                      ; preds = %0, %5
  %2 = phi i2 [ 0, %0 ], [ %7, %5 ]
  switch i2 %2, label %4 [
    i2 0, label %5
    i2 1, label %3
    i2 -2, label %9
  ]

; <label>:3:                                      ; preds = %1
  br label %5, !dbg !826

; <label>:4:                                      ; preds = %1
  unreachable, !dbg !824

; <label>:5:                                      ; preds = %1, %3
  %6 = phi i32 [ 3, %3 ], [ 1, %1 ]
  %7 = phi i2 [ -2, %3 ], [ 1, %1 ]
  %8 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([3 x i8],
[3 x i8]* @.str, i64 0, i64 0), i32 %6), !dbg !828
  br label %1, !dbg !693, !llvm.loop !830

; <label>:9:                                      ; preds = %1
  ret i32 0, !dbg !832
}


Issue:

The optimizer could have optimized the couroutine into something more like the
two sequential calls to printf. Instead, it isn't able to unroll the
"couroutine-loop".

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20170823/63389475/attachment.html>