Jeff Law <l...@redhat.com> writes:
> On 05/07/2015 05:37 AM, Richard Sandiford wrote:
>> One problem with the automatically-generated gen_rtx_FOO () macros
>> is that they always have a mode parameter, even for codes like SET
>> where the mode should always be VOIDmode. This inevitably leads to
>> cases where a caller accidentally passes something other than VOIDmode.
>> E.g. when expanding an SImode move, the temptation is to make everything
>> SImode, even the SETs. This in turn can cause two instructions to appear
>> different simply because their SETs have different modes, even though the
>> SET_DEST and SET_SRC are identical.
>>
>> E.g. for gcc/testsuite/g++.dg/torture/pr34651.C on lm32-elf we have
>> the following before jump2:
>>
>> (jump_insn 42 191 43 5 (set (pc)
>> (if_then_else (eq:SI (reg:SI 13 r13 [orig:43 inHotKey$4+-3 ] [43])
>> (const_int 0 [0]))
>> (label_ref 53)
>> (pc))) gcc/testsuite/g++.dg/torture/pr34651.C:22 22 {*beq}
>> (expr_list:REG_DEAD (reg:SI 13 r13 [orig:43 inHotKey$4+-3 ] [43])
>> (int_list:REG_BR_PROB 5000 (nil)))
>> -> 53)
>> (note 43 42 48 6 [bb 6] NOTE_INSN_BASIC_BLOCK)
>> (insn 48 43 47 6 (set (reg:SI 2 r2)
>> (mem/u/c:SI (reg:SI 1 r1) [4 S4 A32]))
>> gcc/testsuite/g++.dg/torture/pr34651.C:22 7 {movsi_insn}
>> (expr_list:REG_DEAD (reg:SI 1 r1)
>> (nil)))
>> [...]
>> (code_label 53 169 54 7 6 "" [1 uses])
>> (note 54 53 12 7 [bb 7] NOTE_INSN_BASIC_BLOCK)
>> (insn 12 54 57 7 (set:SI (reg/f:SI 2 r2 [orig:46 D.2050 ] [46])
>> (mem/u/c:SI (reg:SI 1 r1) [4 S4 A32]))
>> gcc/testsuite/g++.dg/torture/pr34651.C:22 7 {movsi_insn}
>> (expr_list:REG_DEAD (reg:SI 1 r1)
>> (expr_list:REG_EQUAL (symbol_ref/f:SI ("*.LC3") [flags 0x2]
>> <var_decl # *.LC3>)
>> (nil))))
>>
>> where insns 12 and 48 are identical except for the :SI on the SET.
>> This difference prevents us from merging the heads of the two blocks;
>> after removing it we replace the two loads with a single load before
>> the branch.
>>
>> This patch removes the mode argument from gen_rtx_SET and updates
>> all callers. I used a script to (try to) make sure that all callers
>> really had been caught. I also built one target per CPU just in case.
>> There were some changes in gcc.dg, g++.dg and gcc.c-torture assembly
>> code for c6x-elf, lm32-elf and v850-elf, but all of them seemed to be
>> code improvements from removing duplicated instructions. (Other ports
>> also passed spurious modes but apparently not in a way that affects
>> the tests I'd tried.) Also tested on x86_64-linux-gnu. OK to install?
>>
>> BTW, I've split the patch up into two, the last bit being a mechanical
>> removal of modes. (I did it by hand though to try to keep things
>> properly formatted.)
>>
>> Thanks,
>> Richard
>>
>>
>> gcc/
>> * rtl.h (always_void_p): New function.
>> * gengenrtl.c (always_void_p(: Likewise.
> Typo in the ChangeLog.
>
> non-mechanical part didn't seem to be attached. I don't expect any
> problems there, but a quick looksie seems appropriate.
Bah. Sorry about that.
It's unfortunate that we have two copies of the test -- one on codes
and one on strings -- but that's how everything else in gengenrtl.c
is done. Maybe a later clean-up.
Index: gcc/genemit.c
===================================================================
--- gcc/genemit.c 2015-05-07 07:59:47.890577327 +0100
+++ gcc/genemit.c 2015-05-07 07:59:47.874577523 +0100
@@ -94,6 +94,7 @@ gen_exp (rtx x, enum rtx_code subroutine
int i;
int len;
const char *fmt;
+ const char *sep = "";
if (x == 0)
{
@@ -215,7 +216,12 @@ gen_exp (rtx x, enum rtx_code subroutine
printf ("gen_rtx_");
print_code (code);
- printf (" (%smode", GET_MODE_NAME (GET_MODE (x)));
+ printf (" (");
+ if (!always_void_p (code))
+ {
+ printf ("%smode", GET_MODE_NAME (GET_MODE (x)));
+ sep = ",\n\t";
+ }
fmt = GET_RTX_FORMAT (code);
len = GET_RTX_LENGTH (code);
@@ -223,7 +229,7 @@ gen_exp (rtx x, enum rtx_code subroutine
{
if (fmt[i] == '0')
break;
- printf (",\n\t");
+ fputs (sep, stdout);
switch (fmt[i])
{
case 'e': case 'u':
@@ -254,6 +260,7 @@ gen_exp (rtx x, enum rtx_code subroutine
default:
gcc_unreachable ();
}
+ sep = ",\n\t";
}
printf (")");
}
Index: gcc/gengenrtl.c
===================================================================
--- gcc/gengenrtl.c 2015-05-07 07:59:47.890577327 +0100
+++ gcc/gengenrtl.c 2015-05-07 08:12:24.281310491 +0100
@@ -116,6 +116,14 @@ special_format (const char *fmt)
|| strchr (fmt, 'n') != 0);
}
+/* Return true if CODE always has VOIDmode. */
+
+static inline bool
+always_void_p (int idx)
+{
+ return strcmp (defs[idx].enumname, "SET") == 0;
+}
+
/* Return nonzero if the RTL code given by index IDX is one that we should
generate a gen_rtx_raw_FOO macro for, not gen_rtx_FOO (because gen_rtx_FOO
is a wrapper in emit-rtl.c). */
@@ -181,6 +189,7 @@ find_formats (void)
genmacro (int idx)
{
const char *p;
+ const char *sep = "";
int i;
/* We write a macro that defines gen_rtx_RTLCODE to be an equivalent to
@@ -190,15 +199,25 @@ genmacro (int idx)
/* Don't define a macro for this code. */
return;
- printf ("#define gen_rtx_%s%s(MODE",
+ bool has_mode_p = !always_void_p (idx);
+ printf ("#define gen_rtx_%s%s(",
special_rtx (idx) ? "raw_" : "", defs[idx].enumname);
+ if (has_mode_p)
+ {
+ printf ("MODE");
+ sep = ", ";
+ }
for (p = defs[idx].format, i = 0; *p != 0; p++)
if (*p != '0')
- printf (", ARG%d", i++);
-
- printf (") \\\n gen_rtx_fmt_%s (%s, (MODE)",
- defs[idx].format, defs[idx].enumname);
+ {
+ printf ("%sARG%d", sep, i++);
+ sep = ", ";
+ }
+
+ printf (") \\\n gen_rtx_fmt_%s (%s, %s",
+ defs[idx].format, defs[idx].enumname,
+ has_mode_p ? "(MODE)" : "VOIDmode");
for (p = defs[idx].format, i = 0; *p != 0; p++)
if (*p != '0')
Index: gcc/rtl.h
===================================================================
--- gcc/rtl.h 2015-05-07 07:59:47.890577327 +0100
+++ gcc/rtl.h 2015-05-07 08:11:56.405652046 +0100
@@ -1787,6 +1787,14 @@ #define COSTS_N_INSNS(N) ((N) * 4)
not to use an rtx with this cost under any circumstances. */
#define MAX_COST INT_MAX
+/* Return true if CODE always has VOIDmode. */
+
+static inline bool
+always_void_p (enum rtx_code code)
+{
+ return code == SET;
+}
+
/* A structure to hold all available cost information about an rtl
expression. */
struct full_rtx_costs
@@ -3597,5 +3605,4 @@ #define fatal_insn_not_found(insn) \
/* reginfo.c */
extern tree GTY(()) global_regs_decl[FIRST_PSEUDO_REGISTER];
-
#endif /* ! GCC_RTL_H */
