Add missing __builtin_bitreverse8

[arsenm]

Summary

Also add documentation for bitreverse builtins

[arsenm]

ping

[arsenm]

I directly copied this from the bit reverse intrinsic documentation, so that will need to be fixed too

---

From: Arthur O'Dwyer <[e-mail]>
Sent: Monday, March 7, 2016 11:56 AM
To: [e-mail]; Arsenault, Matthew
Subject: Re: [PATCH] D16993: Add missing __builtin_bitreverse8

[arsenm]

ping

[rsmith]

docs/LanguageExtensions.rst

1533

This example doesn't make much sense: it looks like it's bit reversing a 7 bit number containing non-binary digits? Can you provide a real example instead?

[arsenm]

docs/LanguageExtensions.rst

1533

This was copied from the IR description. I fixed it there, I'll fix it again here

[arsenm]

r264203

docs/LanguageExtensions.rst

 argument.
 
 The result of ``__builtin_convertvector`` is a vector with the same element
 type as the second argument, with a value defined in terms of the action of a
 C-style cast applied to each element of the first argument.
 
 Query for this feature with ``__has_builtin(__builtin_convertvector)``.
 
+``__builtin_bitreverse``
+---------------------
+
+* ``__builtin_bitreverse8``
+* ``__builtin_bitreverse16``
+* ``__builtin_bitreverse32``
+* ``__builtin_bitreverse64``
+
+**Syntax**:
+
+.. code-block:: c++
+     __builtin_bitreverse32(x)
+
+**Examples**:
+
+.. code-block:: c++
+      uint8_t rev_x = __builtin_bitreverse8(x);
+      uint16_t rev_x = __builtin_bitreverse16(x);
+      uint32_t rev_y = __builtin_bitreverse32(y);
+      uint64_t rev_z = __builtin_bitreverse64(z);
+
+**Description**:
+
+The '``__builtin_bitreverse``' family of builtins is used to reverse
+the bitpattern of an integer value; for example ``0b1234567`` becomes
+``0b7654321``.
+
 ``__builtin_unreachable``
 -------------------------
 
 ``__builtin_unreachable`` is used to indicate that a specific point in the
 program cannot be reached, even if the compiler might otherwise think it can.
 This is useful to improve optimization and eliminates certain warnings.  For
 example, without the ``__builtin_unreachable`` in the example below, the
 compiler assumes that the inline asm can fall through and prints a "function

include/clang/Basic/Builtins.def

 BUILTIN(__builtin_popcountll, "iULLi", "nc")
 
 // FIXME: These type signatures are not correct for targets with int != 32-bits
 // or with ULL != 64-bits.
 BUILTIN(__builtin_bswap16, "UsUs", "nc")
 BUILTIN(__builtin_bswap32, "UiUi", "nc")
 BUILTIN(__builtin_bswap64, "ULLiULLi", "nc")
 
+BUILTIN(__builtin_bitreverse8, "UcUc", "nc")
 BUILTIN(__builtin_bitreverse16, "UsUs", "nc")
 BUILTIN(__builtin_bitreverse32, "UiUi", "nc")
 BUILTIN(__builtin_bitreverse64, "ULLiULLi", "nc")
 
 // Random GCC builtins
 BUILTIN(__builtin_constant_p, "i.", "nctu")
 BUILTIN(__builtin_classify_type, "i.", "nctu")
 BUILTIN(__builtin___CFStringMakeConstantString, "FC*cC*", "nc")

test/CodeGen/builtins.c

#define V(n,args) p(#n #args, (__builtin_##n args, 0))
   P(object_size, (s0, 3));
 
   // Whatever
 
   P(bswap16, (N));
   P(bswap32, (N));
   P(bswap64, (N));
 
+  // CHECK: @llvm.bitreverse.i8
   // CHECK: @llvm.bitreverse.i16
   // CHECK: @llvm.bitreverse.i32
   // CHECK: @llvm.bitreverse.i64
+  P(bitreverse8, (N));
   P(bitreverse16, (N));
   P(bitreverse32, (N));
   P(bitreverse64, (N));
 
   // FIXME
   // V(clear_cache, (&N, &N+1));
   V(trap, ());
   R(extract_return_addr, (&N));