The following fixes redundant hard-register "stores" to be not eliminated
by FRE/PRE and the alias machinery to properly handle different
local VAR_DECLs with the same asm specification.
Comments are welcome. I tested the testcase on x86_64, ppc64le and
aarch64 and all seem to be happy with *4 as register specification.
Bootstrap / regtest running on x86_64-unknown-linux-gnu.
Richard.
2017-04-25 Richard Biener <rguent...@suse.de>
PR tree-optimization/80492
* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
Do not eliminate redundant hardregister stores.
* alias.c (compare_base_decls): Handle registers with asm
specification conservatively.
* tree-ssa-alias.c (decl_refs_may_alias_p): Handle
compare_base_decls returning dont-know properly.
* gcc.dg/pr80492.c: New testcase.
Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c (revision 247095)
--- gcc/tree-ssa-pre.c (working copy)
*************** eliminate_dom_walker::before_dom_childre
*** 4495,4500 ****
--- 4519,4526 ----
if (gimple_assign_single_p (stmt)
&& !gimple_has_volatile_ops (stmt)
&& !is_gimple_reg (gimple_assign_lhs (stmt))
+ && !(TREE_CODE (gimple_assign_lhs (stmt)) == VAR_DECL
+ && DECL_HARD_REGISTER (gimple_assign_lhs (stmt)))
&& (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
|| is_gimple_min_invariant (gimple_assign_rhs1 (stmt))))
{
Index: gcc/alias.c
===================================================================
*** gcc/alias.c (revision 247095)
--- gcc/alias.c (working copy)
*************** compare_base_decls (tree base1, tree bas
*** 2046,2051 ****
--- 2046,2063 ----
if (base1 == base2)
return 1;
+ /* If we have two register decls with register specification we
+ cannot decide unless their assembler name is the same. */
+ if (DECL_REGISTER (base1)
+ && DECL_REGISTER (base2)
+ && DECL_ASSEMBLER_NAME_SET_P (base1)
+ && DECL_ASSEMBLER_NAME_SET_P (base2))
+ {
+ if (DECL_ASSEMBLER_NAME (base1) == DECL_ASSEMBLER_NAME (base2))
+ return 1;
+ return -1;
+ }
+
/* Declarations of non-automatic variables may have aliases. All other
decls are unique. */
if (!decl_in_symtab_p (base1)
Index: gcc/tree-ssa-alias.c
===================================================================
*** gcc/tree-ssa-alias.c (revision 247095)
--- gcc/tree-ssa-alias.c (working copy)
*************** decl_refs_may_alias_p (tree ref1, tree b
*** 1096,1116 ****
{
gcc_checking_assert (DECL_P (base1) && DECL_P (base2));
/* If both references are based on different variables, they cannot alias.
*/
! if (compare_base_decls (base1, base2) == 0)
return false;
/* If both references are based on the same variable, they cannot alias if
the accesses do not overlap. */
! if (!ranges_overlap_p (offset1, max_size1, offset2, max_size2))
! return false;
! /* For components with variable position, the above test isn't sufficient,
! so we disambiguate component references manually. */
! if (ref1 && ref2
! && handled_component_p (ref1) && handled_component_p (ref2)
! && nonoverlapping_component_refs_of_decl_p (ref1, ref2))
! return false;
return true;
}
--- 1128,1153 ----
{
gcc_checking_assert (DECL_P (base1) && DECL_P (base2));
+ int cmp = compare_base_decls (base1, base2);
+
/* If both references are based on different variables, they cannot alias.
*/
! if (cmp == 0)
return false;
/* If both references are based on the same variable, they cannot alias if
the accesses do not overlap. */
! if (cmp == 1)
! {
! if (!ranges_overlap_p (offset1, max_size1, offset2, max_size2))
! return false;
! /* For components with variable position, the above test isn't
sufficient,
! so we disambiguate component references manually. */
! if (ref1 && ref2
! && handled_component_p (ref1) && handled_component_p (ref2)
! && nonoverlapping_component_refs_of_decl_p (ref1, ref2))
! return false;
! }
return true;
}
Index: gcc/testsuite/gcc.dg/pr80492.c
===================================================================
*** gcc/testsuite/gcc.dg/pr80492.c (nonexistent)
--- gcc/testsuite/gcc.dg/pr80492.c (working copy)
***************
*** 0 ****
--- 1,20 ----
+ /* { dg-do compile } */
+ /* { dg-options "-w -O2 -fdump-tree-optimized" } */
+
+ static __inline__ __attribute__((__always_inline__))
+ void syscall_7 (int val)
+ {
+ register int reg __asm ("4") = val;
+ __asm __volatile__ ("/* Some Code %0 */" :: "r" (reg));
+ }
+
+ void do_syscalls (void)
+ {
+ for (int s = 0; s < 2; s++)
+ {
+ syscall_7 (0);
+ syscall_7 (1);
+ }
+ }
+
+ /* { dg-final { scan-tree-dump-times "reg = " 4 "optimized" } } */
