[LLVMbugs] [Bug 22629] New: Missed optimization: accessing a single-element array

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=22629

            Bug ID: 22629
           Summary: Missed optimization: accessing a single-element array
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: sami.liedes at iki.fi
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Consider this code:

  int f(int x) {
    int a[] = {12};
    return a[x];
  }

GCC knows to optimize this to

  movl     $12, %eax
  ret

The code generated by recent Clang at -O3 is:

  movslq   %edi, %rax
  movl     .L_ZZ1fiE1a(,%rax,4), %eax
  retq

.L_ZZ1fiE1a:
  .long    12                      # 0xc

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