On 19-06-14 07:13, Richard Henderson wrote:
On 05/19/2014 07:30 AM, Tom de Vries wrote:
+ for (insn = get_insns (); insn != NULL_RTX; insn = next_insn (insn))
+ {
+ HARD_REG_SET insn_used_regs;
+
+ if (!NONDEBUG_INSN_P (insn))
+ continue;
+
+ find_all_hard_reg_sets (insn, &insn_used_regs, false);
+
+ if (CALL_P (insn)
+ && !get_call_reg_set_usage (insn, &insn_used_regs, call_used_reg_set))
+ {
+ CLEAR_HARD_REG_SET (node->function_used_regs);
+ return;
+ }
+
+ IOR_HARD_REG_SET (node->function_used_regs, insn_used_regs);
+ }
<SNIP>
Let's suppose that we've got a rather large function, with only local calls for
which we can acquire usage. Let's suppose that even one of those callees
further calls something else, such that insn_used_regs == call_used_reg_set.
We fill node->function_used_regs immediately, but keep scanning the rest of the
large function.
+
+ /* Be conservative - mark fixed and global registers as used. */
+ IOR_HARD_REG_SET (node->function_used_regs, fixed_reg_set);
+ for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+ if (global_regs[i])
+ SET_HARD_REG_BIT (node->function_used_regs, i);
+
+#ifdef STACK_REGS
+ /* Handle STACK_REGS conservatively, since the df-framework does not
+ provide accurate information for them. */
+
+ for (i = FIRST_STACK_REG; i <= LAST_STACK_REG; i++)
+ SET_HARD_REG_BIT (node->function_used_regs, i);
+#endif
+
+ node->function_used_regs_valid = 1;
Wouldn't it be better to compare the collected function_used_regs; if it
contains all of call_used_reg_set, decline to set function_used_regs_valid.
That way, we'll early exit from the above loop whenever we see that we can't
improve over the default call-clobber set.
Richard,
Agreed. Attached patch implements this (on top of the minor rewrite of
https://gcc.gnu.org/ml/gcc-patches/2014-06/msg01535.html ).
Although perhaps function_used_regs_valid is no longer the best name in that
case...
I think the name is still ok. The field function_used_regs_valid just states
that the function_used_regs field is valid and can be used.
OK for trunk if bootstrap and reg-test on x86_64 is ok ?
Thanks,
- Tom
2014-06-19 Tom de Vries <t...@codesourcery.com>
* final.c (collect_fn_hard_reg_usage): Don't save function_used_regs if
it contains all call_used_regs.
diff --git a/gcc/final.c b/gcc/final.c
index e39930d..e67e84b 100644
--- a/gcc/final.c
+++ b/gcc/final.c
@@ -4795,6 +4795,11 @@ collect_fn_hard_reg_usage (void)
SET_HARD_REG_BIT (function_used_regs, i);
#endif
+ /* The information we have gathered is only interesting if it exposes a
+ register from the call_used_regs that is not used in this function. */
+ if (hard_reg_set_subset_p (call_used_reg_set, function_used_regs))
+ return;
+
node = cgraph_rtl_info (current_function_decl);
gcc_assert (node != NULL);
--
1.9.1
