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    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - [X86] Intrinsics _bit_scan_forward is hidden when _MSC_VER is defined"
   href="https://bugs.llvm.org/show_bug.cgi?id=33722">33722</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>[X86] Intrinsics _bit_scan_forward is hidden when _MSC_VER is defined
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Windows NT
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>enhancement
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Headers
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>zvi.rackover@intel.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>cat test.c:

 #define _MSC_VER
 #include <immintrin.h>

 int test_bit_scan_forward(int a) {
   return _bit_scan_forward(a);
 }

clang -cc1 -internal-isystem llvm/build/lib/clang/5.0.0/include -nostdsysteminc
-ffreestanding -trip
le x86_64-unknown-unknown -emit-llvm -o - test.c

results with:

...
define i32 @test_bit_scan_forward(i32 %a) #0 {
entry:
  %a.addr = alloca i32, align 4
  store i32 %a, i32* %a.addr, align 4
  %0 = load i32, i32* %a.addr, align 4
  %call = call i32 (i32, ...) bitcast (i32 (...)* @_bit_scan_forward to i32
(i32, ...)*)(i32 %0) #2
  ret i32 %call
}

declare i32 @_bit_scan_forward(...) #1
...

'_bit_scan_forward' is an intrinsics function which is lowered to an external
function call.

Same issue with _bit_scan_reverse.</pre>
        </div>
      </p>


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