On Wed, Jan 22, 2020 at 03:24:54PM +0100, Jakub Jelinek wrote:
> > It looks like your patch will pessimise code in some cases as well, btw?
>
> No, it will solely turn previous wrong-codes into something that works
> (== cases where gen_addr3_insn would previously fail).
> The 1)+2) variant could even improve code, as gen_addr3_insn could succeed
> even if we currently don't call it (perhaps generate more than one insn,
> but it still might be better than forcing the constant into register and
> then performing add that way).
Here is what I meant as the alternative, i.e. don't check any predicates,
just gen_add3_insn, if that fails, force rs into register and retry.
And, add REG_FRAME_RELATED_EXPR note always when we haven't emitted a single
insn that has rtl exactly matching what we'd add the REG_FRAME_RELATED_EXPR
with (in that case, dwarf2cfi.c is able to figure it out by itself, no need
to waste compile time memory).
Ok for trunk if it passes bootstrap/regtest?
2020-01-30 Jakub Jelinek <ja...@redhat.com>
PR target/93122
* config/rs6000/rs6000-logue.c
(rs6000_emit_probe_stack_range_stack_clash): Always use gen_add3_insn,
if it fails, move rs into end_addr and retry. Add
REG_FRAME_RELATED_EXPR note whenever it returns more than one insn or
the insn pattern doesn't describe well what exactly happens to
dwarf2cfi.c.
* gcc.target/powerpc/pr93122.c: New test.
--- gcc/config/rs6000/rs6000-logue.c.jj 2020-01-12 11:54:36.395413680 +0100
+++ gcc/config/rs6000/rs6000-logue.c 2020-01-30 16:54:28.646943559 +0100
@@ -1604,20 +1604,32 @@ rs6000_emit_probe_stack_range_stack_clas
rtx end_addr
= copy_reg ? gen_rtx_REG (Pmode, 0) : gen_rtx_REG (Pmode, 12);
rtx rs = GEN_INT (-rounded_size);
- rtx_insn *insn;
- if (add_operand (rs, Pmode))
- insn = emit_insn (gen_add3_insn (end_addr, stack_pointer_rtx, rs));
- else
+ rtx_insn *insn = gen_add3_insn (end_addr, stack_pointer_rtx, rs);
+ if (insn == NULL)
+ {
+ emit_move_insn (end_addr, rs);
+ insn = gen_add3_insn (end_addr, end_addr, stack_pointer_rtx);
+ gcc_assert (insn);
+ }
+ rtx set;
+ if (!NONJUMP_INSN_P (insn)
+ || NEXT_INSN (insn)
+ || (set = single_set (insn)) == NULL_RTX
+ || SET_DEST (set) != end_addr
+ || GET_CODE (SET_SRC (set)) != PLUS
+ || XEXP (SET_SRC (set), 0) != stack_pointer_rtx
+ || XEXP (SET_SRC (set), 1) != rs)
{
- emit_move_insn (end_addr, GEN_INT (-rounded_size));
- insn = emit_insn (gen_add3_insn (end_addr, end_addr,
- stack_pointer_rtx));
- /* Describe the effect of INSN to the CFI engine. */
+ insn = emit_insn (insn);
+ /* Describe the effect of INSN to the CFI engine, unless it
+ is a single insn that describes it itself. */
add_reg_note (insn, REG_FRAME_RELATED_EXPR,
gen_rtx_SET (end_addr,
gen_rtx_PLUS (Pmode, stack_pointer_rtx,
rs)));
}
+ else
+ insn = emit_insn (insn);
RTX_FRAME_RELATED_P (insn) = 1;
/* Emit the loop. */
--- gcc/testsuite/gcc.target/powerpc/pr93122.c.jj 2020-01-30
16:42:14.255927311 +0100
+++ gcc/testsuite/gcc.target/powerpc/pr93122.c 2020-01-30 16:42:14.255927311
+0100
@@ -0,0 +1,12 @@
+/* PR target/93122 */
+/* { dg-do compile { target lp64 } } */
+/* { dg-options "-fstack-clash-protection -mprefixed-addr -mfuture" } */
+
+void bar (char *);
+
+void
+foo (void)
+{
+ char s[4294967296];
+ bar (s);
+}
Jakub
