[llvm-bugs] [Bug 37541] New: [NewGVN] assumes are optimized away

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37541

            Bug ID: 37541
           Summary: [NewGVN] assumes are optimized away
           Product: libraries
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: nikita.ppv at gmail.com
                CC: llvm-bugs at lists.llvm.org

Just to make sure this is documented, NewGVN optimizes

define {}* @test({}* %arg) {
  %cmp = icmp ne {}* %arg, null
  call void @llvm.assume(i1 %cmp)
  ret {}* %arg
}
declare void @llvm.assume(i1)

into

define {}* @test({}* %arg) {
  %cmp = icmp ne {}* %arg, null
  call void @llvm.assume(i1 true)
  ret {}* %arg
}
declare void @llvm.assume(i1)

That is, assumes will usually be reduced to "i1 true" (unless no predicate info
is inserted). This should be prevented.

-- 
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/20180521/8a6f84d9/attachment.html>