[patch] if-conversion of loops with conditionals containing memory loads and stores

[Sebastian Pop]

Hi,

The attached patches (on top of the previous patch set) are needed to
if-convert the DCT loop kernel of FFmpeg.

0009 replaces the memory writes that are in predicated basic blocks
with a full write: "if (cond) A[i] = foo" is replaced with "A[i] =
cond ? foo : A[i]".  In order to do this, the patch replaces the call
to gimple_assign_rhs_could_trap_p with gimple_could_trap_p, as we now
have to check that the LHS of assign stmts in conditions do not trap.

In order to if-convert the DCT kernel:

  for (i = 0; i <= nCoeffs; i++)
    {
      level = block[i];
      if (level)
       {
         if (level < 0)
           {
             level = level * qmul - qadd;
           }
         else
           {
             level = level * qmul + qadd;
           }
         block[i] = level;
       }
    }

0010 proves that the accesses to an array in a loop do not trap (more
(than the original non-if-converted loop)) if they are executed at
every iteration.  In this DCT kernel, the read into block[i] happens
at every iteration, and thus the if-converted writes into block[i]
will not trap more than the original code.

The attached patches are the same as previously posted, with the
exception of this part from 0009:

(if_convertible_gimple_assign_stmt_p): Do not handle types that do
not match is_gimple_reg_type.

+  if (!is_gimple_reg_type (TREE_TYPE (lhs)))
+    return false;
+

this makes the patch pass with the extra checks added by Richi to
avoid operands of the COND_EXPR to contain memory loads or stores.

These two patches passed regstrap with BOOT_CFLAGS= -g -O3 -msse2 on
amd64-linux on top of the 8 other patches submitted separately.
Ok for trunk?

Thanks,
Sebastian Pop
--
AMD / Open Source Compiler Engineering / GNU Tools
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