I tracked down the bug with the spec 2006 benchmark WRF using the LRA register
allocator.
At one point LRA has decided to use the CTR to hold a CCmode value:
(insn 11019 11018 11020 16 (set (reg:CC 66 ctr [4411])
(reg:CC 66 ctr [4411])) module_diffusion_em.fppized.f90:4885 360
{*movcc_internal1}
(expr_list:REG_DEAD (reg:CC 66 ctr [4411])
(nil)))
Now movcc_internal1 has moves from r->h (which includes ctr/lr) and ctr/lr->r,
but it doesn't have a move to cover the nop move of moving the ctr to the ctr.
IMHO, LRA should not be generating NOP moves that are later deleted.
There are two ways to solve the problem. One is not to let anything but int
modes into CTR/LR, which will also eliminate the register allocator from
spilling floating point values there (which we've seen in the past, but the
last time I tried to eliminate it I couldn't). The following patch does this,
and also changes the assertion to call fatal_insn_not_found to make it clearer
what the error is.
I imagine, I could add a NOP move insn to movcc_internal1, but that just
strikes me as wrong.
Note, this does not fix the 32-bit failure in dealII, and I also noticed that I
can't bootstrap the compiler using --with-cpu=power7, which I will get to
tomorrow.
2013-04-16 Michael Meissner <meiss...@linux.vnet.ibm.com>
* config/rs6000/rs6000.opt (-mconstrain-regs): New debug switch to
control whether we only allow int modes to go in the CTR, LR,
VRSAVE, VSCR registers.
* config/rs6000/rs6000.c (rs6000_hard_regno_mode_ok): Likewise.
(rs6000_debug_reg_global): If -mdebug=reg, print out if SPRs are
constrained.
(rs6000_option_override_internal): Set -mconstrain-regs if we are
using the LRA register allocator.
* lra.c (check_rtl): Use fatal_insn_not_found to report constraint
does not match.
--
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460, USA
email: meiss...@linux.vnet.ibm.com, phone: +1 (978) 899-4797
Index: gcc/config/rs6000/rs6000.opt
===================================================================
--- gcc/config/rs6000/rs6000.opt (revision 197925)
+++ gcc/config/rs6000/rs6000.opt (working copy)
@@ -522,3 +522,7 @@ Control whether we save the TOC in the p
mvsx-timode
Target Undocumented Mask(VSX_TIMODE) Var(rs6000_isa_flags)
; Allow/disallow TImode in VSX registers
+
+mconstrain-regs
+Target Undocumented Mask(CONSTRAIN_REGS) Var(rs6000_isa_flags)
+; Only allow ints of certain modes to go in SPRs
Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c (revision 197925)
+++ gcc/config/rs6000/rs6000.c (working copy)
@@ -1608,6 +1608,18 @@ rs6000_hard_regno_mode_ok (int regno, en
if (SPE_SIMD_REGNO_P (regno) && TARGET_SPE && SPE_VECTOR_MODE (mode))
return 1;
+ /* See if we need to be stricter about what goes into the special
+ registers (LR, CTR, VSAVE, VSCR). */
+ if (TARGET_CONSTRAIN_REGS)
+ {
+ if (regno == LR_REGNO || regno == CTR_REGNO)
+ return (GET_MODE_CLASS (mode) == MODE_INT
+ && rs6000_hard_regno_nregs[mode][regno] == 1);
+
+ if (regno == VRSAVE_REGNO || regno == VSCR_REGNO)
+ return (mode == SImode);
+ }
+
/* We cannot put non-VSX TImode or PTImode anywhere except general register
and it must be able to fit within the register set. */
@@ -2054,6 +2066,9 @@ rs6000_debug_reg_global (void)
if (targetm.lra_p ())
fprintf (stderr, DEBUG_FMT_S, "lra", "true");
+ if (TARGET_CONSTRAIN_REGS)
+ fprintf (stderr, DEBUG_FMT_S, "constrain-regs", "true");
+
fprintf (stderr, DEBUG_FMT_S, "plt-format",
TARGET_SECURE_PLT ? "secure" : "bss");
fprintf (stderr, DEBUG_FMT_S, "struct-return",
@@ -2945,6 +2960,12 @@ rs6000_option_override_internal (bool gl
}
}
+ /* If we are using the LRA register allocator, constrain the SPRs to only
+ have integer modes, and not modes like CC. */
+ if ((rs6000_isa_flags_explicit & OPTION_MASK_CONSTRAIN_REGS) == 0
+ && targetm.lra_p ())
+ rs6000_isa_flags |= OPTION_MASK_CONSTRAIN_REGS;
+
/* Place FP constants in the constant pool instead of TOC
if section anchors enabled. */
if (flag_section_anchors)
Index: gcc/lra.c
===================================================================
--- gcc/lra.c (revision 197925)
+++ gcc/lra.c (working copy)
@@ -1996,7 +1996,8 @@ check_rtl (bool final_p)
if (final_p)
{
extract_insn (insn);
- lra_assert (constrain_operands (1));
+ if (!constrain_operands (1))
+ fatal_insn_not_found (insn);
continue;
}
if (insn_invalid_p (insn, false))
