[llvm-bugs] [Bug 44543] New: InstCombine should correctly propagate alignment

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=44543

            Bug ID: 44543
           Summary: InstCombine should correctly propagate alignment
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: juneyoung.lee at sf.snu.ac.kr
                CC: llvm-bugs at lists.llvm.org

Created attachment 23016
  --> https://bugs.llvm.org/attachment.cgi?id=23016&action=edit
input.ll

```
$ cat input.ll
target datalayout = "p:64:64:64-i64:32:32"

define i64* @test1(i8* %x) {
entry:
  %p = bitcast i8* %x to i64*
  %b1 = load i64, i64* %p
  %p2 = inttoptr i64 %b1 to i64*
  ret i64* %p2
}
$ opt -instcombine input.ll -S -o -
target datalayout = "p:64:64:64-i64:32:32"
define i64* @test1(i8* %x) {
entry:
  %0 = bitcast i8* %x to i64**
  %b11 = load i64*, i64** %0, align 8
  ret i64* %b11
}
```

The updated load should have align 4 because data layout says i64 has 4-bytes
alignment.

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