So the m68k port has failed to bootstrap since the introduction of
late-combine. My suspicion has been this is a backend problem. Sure
enough after bisecting things down (thank goodness for the debug
counter!) I'm happy to report m68k will bootstrap, though it's failing
the comparison check.
Basically late-combine propagated an address calculation to its use
points, generating this insn (dwarf2out.c, I forget what function):
(insn 653 652 655 (parallel [
(set (mem/j:DI (plus:SI (plus:SI (reg/f:SI 9 %a1 [orig:64 _67 ]
[64])
(reg:SI 0 %d0 [321]))
(const_int 20 [0x14])) [0
slot_204->dw_attr_val.v.val_unsigned+0 S8 A16])
(sign_extend:DI (mem/c:SI (plus:SI (reg/f:SI 14 %a6)
(const_int -28 [0xffffffffffffffe4])) [870 %sfp+-28
S4 A16])))
(clobber (reg:SI 0 %d0))
]) "../../../gcc/gcc/dwarf2out.cc":24961:23 93 {extendsidi2}
(expr_list:REG_DEAD (reg/f:SI 9 %a1 [orig:64 _67 ] [64])
(expr_list:REG_DEAD (reg:SI 0 %d0 [321])
(expr_list:REG_UNUSED (reg:SI 0 %d0)
(nil)))))
Note how the output uses d0 in the address calculation and the clobber
uses d0.
It matches this insn in the md file:
(define_insn "extendsidi2"
[(set (match_operand:DI 0 "nonimmediate_operand" "=d,o,o,<")
(sign_extend:DI
(match_operand:SI 1 "nonimmediate_src_operand" "rm,rm,r<Q>,rm")))
(clobber (match_scratch:SI 2 "=X,&d,&d,&d"))]
""
{
if (which_alternative == 0)
/* Handle alternative 0. */
{
if (TARGET_68020 || TARGET_COLDFIRE)
return "move%.l %1,%R0\;smi %0\;extb%.l %0";
else
return "move%.l %1,%R0\;smi %0\;ext%.w %0\;ext%.l %0";
}
/* Handle alternatives 1, 2 and 3. We don't need to adjust address by 4
in alternative 3 because autodecrement will do that for us. */
operands[3] = adjust_address (operands[0], SImode,
which_alternative == 3 ? 0 : 4);
operands[0] = adjust_address (operands[0], SImode, 0);
if (TARGET_68020 || TARGET_COLDFIRE)
return "move%.l %1,%3\;smi %2\;extb%.l %2\;move%.l %2,%0";
else
return "move%.l %1,%3\;smi %2\;ext%.w %2\;ext%.l %2\;move%.l %2,%0";
}
[(set_attr "ok_for_coldfire" "yes,no,yes,yes")])
Note the smi/ext instruction pair in the case for alternatives 1..3.
Those clobber the scratch register before we're done consuming inputs.
The scratch register really needs to be marked as an earlyclobber.
That fixes the bootstrap segfault. We've still got a comparison
failure, but it's definitely a step in the right direction.
jeff
diff --git a/gcc/config/m68k/m68k.md b/gcc/config/m68k/m68k.md
index 037978db40c..e5c25288844 100644
--- a/gcc/config/m68k/m68k.md
+++ b/gcc/config/m68k/m68k.md
@@ -1887,7 +1887,7 @@ (define_insn "extendsidi2"
[(set (match_operand:DI 0 "nonimmediate_operand" "=d,o,o,<")
(sign_extend:DI
(match_operand:SI 1 "nonimmediate_src_operand" "rm,rm,r<Q>,rm")))
- (clobber (match_scratch:SI 2 "=X,d,d,d"))]
+ (clobber (match_scratch:SI 2 "=X,&d,&d,&d"))]
""
{
if (which_alternative == 0)
