[Bug rtl-optimization/21970] [3.4 only] Inline keyword causes computation to erroneously reduce to a constant

["rsandifo at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From rsandifo at gcc dot gnu dot org  2005-07-04 13:49 -------
Are you sure this reduced testcase is an accurate reflection of the
real one?  The transformation performed by gcc appears to be correct.
For example, r00450DB4 evaluates to 0, so anything ANDed with it
does too.

Here's an attempt to show why.  I've snipped part of the code and
annotated it with comments of the form:

    <rhs> = op (<lhs>) :<nonzero bits>

where <lhs> uses "_" for "don't care" values.  <nonzero bits> is the
mask of bits that _might_ be nonzero.  In other words, zero bits
mean "known to be zero" and one bits mean "value unknown".

-------------------------------------------------------------------------------
UINT32 r004458AC = opt_and(w00, 0x5A827999);	  // A = and (_, cst) :5a827999
UINT32 r00445934 = opt_and(r004457EC, r004458AC); // B = and (_, A)   :5a827999
UINT32 r004459BC = opt_and(r0044572C, r00445934); // C = and (_, B)   :5a827999
...
UINT32 r0044F67C = opt_and(ie, r004459BC);	  // D = and (_, C)   :5a827999
...
UINT32 r0044FA14 = opt_rotl(r0044F67C, 5);	  // E = rotl (D, 5)  :504f332b
UINT32 r0044FAD4 = opt_and(w01, 0x5A827999);	  // F = and (_, cst) :5a827999
UINT32 r0044FB5C = opt_and(r0044FA14, r0044FAD4); // G = and (E, F)   :50023109
UINT32 r0044FBE4 = opt_and(r0044F954, r0044FB5C); // H = and (_, G)   :50023109
UINT32 r0044FC6C = opt_and(id, r0044FBE4);	  // I = and (_, H)   :50023109
...
UINT32 r00450004 = opt_rotl(r0044FC6C, 5);	  // J = rotl (I, 5)  :0046212a
UINT32 r004500C4 = opt_and(w02, 0x5A827999);	  // K = and (_, cst) :5a827999
UINT32 r0045014C = opt_and(r00450004, r004500C4); // L = and (J, K)   :00022108
UINT32 r004501D4 = opt_and(r0044FF44, r0045014C); // M = and (_, L)   :00022108
UINT32 r0045025C = opt_and(ic, r004501D4);	  // N = and (_, M)   :00022108
...
UINT32 r0045031C = opt_rotl(r0044F67C, 30);	  // a = rotl (D, 30) :56a09e66
...
UINT32 r004505F4 = opt_rotl(r0045025C, 5);	  // O = rotl (N, 5)  :00442100
UINT32 r004506B4 = opt_and(w03, 0x5A827999);	  // P = and (_, cst) :5a827999
UINT32 r0045073C = opt_and(r004505F4, r004506B4); // Q = and (O, P)   :00002100
UINT32 r004507C4 = opt_and(r00450534, r0045073C); // R = and (_, Q)   :00002100
UINT32 r0045084C = opt_and(r0044F73C, r004507C4); // S = and (_, R)   :00002100
UINT32 r0045090C = opt_rotl(r0044FC6C, 30);	  // T = rotl (I, 30) :54008c42
UINT32 r00450994 = opt_not(r0045025C);		  // b = not (N)      :fffddef7
UINT32 r00450A14 = opt_and(r00450994, r0045031C); // c = and (b, a)   :56a09e66
...
UINT32 r00450A9C = opt_and(r0045025C, r0045090C); // U = and (N, T)   :00000000
UINT32 r00450B24 = opt_or(r00450A14, r00450A9C);  // V = or (c, U)    :56a09e66
UINT32 r00450BE4 = opt_rotl(r0045084C, 5);	  // W = rotl (S, 5)  :00042000
UINT32 r00450CA4 = opt_and(w04, 0x5A827999);	  // X = and (_, cst) :5a827999
UINT32 r00450D2C = opt_and(r00450BE4, r00450CA4); // Y = and (W, X)   :00002000
UINT32 r00450DB4 = opt_and(r00450B24, r00450D2C); // Z = and (V, Y)   :00000000
-------------------------------------------------------------------------------

PS. Not that it matters for the code quoted above, but your opt_xor
function uses "+" instead of "^".


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rsandifo at gcc dot gnu dot
                   |                            |org
             Status|NEW                         |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21970