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re PR tree-optimization/91482 (__builtin_assume_aligned should not break write combining) 

2019-08-21  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/91482
	* tree-ssa-ccp.c (ccp_folder::fold_stmt): Remove useless
	BUILT_IN_ASSUME_ALIGNED calls.

	* gcc.dg/tree-ssa/pr91482.c: New testcase.

From-SVN: r274796
This commit is contained in:
Richard Biener 2019-08-21 11:45:34 +00:00 committed by Richard Biener
parent 8bb2ee5939
commit d6dea10acf
4 changed files with 50 additions and 0 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2019-08-21 Richard Biener <rguenther@suse.de>
PR tree-optimization/91482
* tree-ssa-ccp.c (ccp_folder::fold_stmt): Remove useless
BUILT_IN_ASSUME_ALIGNED calls.
2019-08-21 Richard Biener <rguenther@suse.de>
PR target/91498

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2019-08-21 Richard Biener <rguenther@suse.de>
PR tree-optimization/91482
* gcc.dg/tree-ssa/pr91482.c: New testcase.
2019-08-21 Eric Botcazou <ebotcazou@adacore.com>
* c-c++-common/dump-ada-spec-15.c: New test.

13
gcc/testsuite/gcc.dg/tree-ssa/pr91482.c Normal file
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@ -0,0 +1,13 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-ccp1 -fdump-tree-store-merging" } */
void write64 (void *p)
{
unsigned *p1 = (unsigned *) __builtin_assume_aligned (p, 8);
*p1++ = 0;
unsigned *p2 = (unsigned *) __builtin_assume_aligned (p1, 4);
*p2++ = 1;
}
/* { dg-final { scan-tree-dump-times "__builtin_assume_aligned" 1 "ccp1" } } */
/* { dg-final { scan-tree-dump "New sequence of 1 stores to replace old one of 2 stores" "store-merging" { target lp64 } } } */

26
gcc/tree-ssa-ccp.c
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@ -2315,6 +2315,32 @@ ccp_folder::fold_stmt (gimple_stmt_iterator *gsi)
}
}
/* If there's no extra info from an assume_aligned call,
drop it so it doesn't act as otherwise useless dataflow
barrier. */
if (gimple_call_builtin_p (stmt, BUILT_IN_ASSUME_ALIGNED))
{
tree ptr = gimple_call_arg (stmt, 0);
ccp_prop_value_t ptrval = get_value_for_expr (ptr, true);
if (ptrval.lattice_val == CONSTANT
&& TREE_CODE (ptrval.value) == INTEGER_CST
&& ptrval.mask != 0)
{
ccp_prop_value_t val
= bit_value_assume_aligned (stmt, NULL_TREE, ptrval, false);
unsigned int ptralign = least_bit_hwi (ptrval.mask.to_uhwi ());
unsigned int align = least_bit_hwi (val.mask.to_uhwi ());
if (ptralign == align
&& ((TREE_INT_CST_LOW (ptrval.value) & (align - 1))
== (TREE_INT_CST_LOW (val.value) & (align - 1))))
{
bool res = update_call_from_tree (gsi, ptr);
gcc_assert (res);
return true;
}
}
}
/* Propagate into the call arguments. Compared to replace_uses_in
this can use the argument slot types for type verification
instead of the current argument type. We also can safely