On Tue, Oct 13, 2015 at 2:52 PM, Richard Biener
<richard.guent...@gmail.com> wrote:
> On Tue, Oct 13, 2015 at 2:21 PM, Jeff Law <l...@redhat.com> wrote:
>>
>> One of the cases that was missing in the FSM support is threading when the
>> path is a single block. ie, a control statement's output can be statically
>> determined just by looking at PHIs in the control statement's block for one
>> or incoming edges.
>>
>> This is necessary to fix a regression if I turn off the old jump threader's
>> backedge support. Just as important, Jan has in the past asked about a
>> trivial jump threader to be run during early optimizations. Limiting the
>> FSM bits to this case would likely satisfy that need in the future.
>
> I think he asked for trivial forward threads though due to repeated tests.
> I hacked FRE to do this (I think), but maybe some trivial cleanup
> opportunities
> are still left here. Honza?
This or other related patches in the range r228731:228774 has caused a quite
big jump in SPEC CPU 2000 binary sizes (notably 176.gcc - so maybe affecting
bootstrap as well, at -O3). Are you sure this doesn't re-introduce DOM
effectively peeling all loops once?
Richard.
> Richard.
>
>> Bootstrapped and regression tested on x86_64-linux-gnu. Installed on the
>> trunk.
>>
>> Jeff
>>
>> commit a53bb29a1dffd329aa6235b88b0c2a830aa5a59e
>> Author: Jeff Law <l...@redhat.com>
>> Date: Tue Oct 13 06:19:20 2015 -0600
>>
>> [PATCH] Allow FSM to thread single block cases too
>>
>> * tree-ssa-threadbackward.c
>> (fsm_find_control_statement_thread_paths):
>> Allow single block jump threading paths.
>>
>> * gcc.dg/tree-ssa/ssa-thread-13.c: New test.
>>
>> diff --git a/gcc/ChangeLog b/gcc/ChangeLog
>> index d71bcd2..caab533 100644
>> --- a/gcc/ChangeLog
>> +++ b/gcc/ChangeLog
>> @@ -1,3 +1,8 @@
>> +2015-10-13 Jeff Law <l...@redhat.com>
>> +
>> + * tree-ssa-threadbackward.c
>> (fsm_find_control_statement_thread_paths):
>> + Allow single block jump threading paths.
>> +
>> 2015-10-13 Tom de Vries <t...@codesourcery.com>
>>
>> PR tree-optimization/67476
>> diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
>> index 4a08f0f..acf6df5 100644
>> --- a/gcc/testsuite/ChangeLog
>> +++ b/gcc/testsuite/ChangeLog
>> @@ -1,3 +1,7 @@
>> +2015-10-13 Jeff Law <l...@redhat.com>
>> +
>> + * gcc.dg/tree-ssa/ssa-thread-13.c: New test.
>> +
>> 2015-10-12 Jeff Law <l...@redhat.com>
>>
>> * gcc.dg/tree-ssa/ssa-thread-12.c: New test.
>> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-13.c
>> b/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-13.c
>> new file mode 100644
>> index 0000000..5051d11
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-13.c
>> @@ -0,0 +1,70 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2 -fdump-tree-vrp1-details" } */
>> +/* { dg-final { scan-tree-dump "FSM" "vrp1" } } */
>> +
>> +typedef struct rtx_def *rtx;
>> +typedef const struct rtx_def *const_rtx;
>> +enum rtx_code
>> +{
>> + UNKNOWN, VALUE, DEBUG_EXPR, EXPR_LIST, INSN_LIST, SEQUENCE, ADDRESS,
>> + DEBUG_INSN, INSN, JUMP_INSN, CALL_INSN, BARRIER, CODE_LABEL, NOTE,
>> + COND_EXEC, PARALLEL, ASM_INPUT, ASM_OPERANDS, UNSPEC, UNSPEC_VOLATILE,
>> + ADDR_VEC, ADDR_DIFF_VEC, PREFETCH, SET, USE, CLOBBER, CALL, RETURN,
>> + EH_RETURN, TRAP_IF, CONST_INT, CONST_FIXED, CONST_DOUBLE, CONST_VECTOR,
>> + CONST_STRING, CONST, PC, REG, SCRATCH, SUBREG, STRICT_LOW_PART, CONCAT,
>> + CONCATN, MEM, LABEL_REF, SYMBOL_REF, CC0, IF_THEN_ELSE, COMPARE, PLUS,
>> + MINUS, NEG, MULT, SS_MULT, US_MULT, DIV, SS_DIV, US_DIV, MOD, UDIV,
>> UMOD,
>> + AND, IOR, XOR, NOT, ASHIFT, ROTATE, ASHIFTRT, LSHIFTRT, ROTATERT, SMIN,
>> + SMAX, UMIN, UMAX, PRE_DEC, PRE_INC, POST_DEC, POST_INC, PRE_MODIFY,
>> + POST_MODIFY, NE, EQ, GE, GT, LE, LT, GEU, GTU, LEU, LTU, UNORDERED,
>> + ORDERED, UNEQ, UNGE, UNGT, UNLE, UNLT, LTGT, SIGN_EXTEND, ZERO_EXTEND,
>> + TRUNCATE, FLOAT_EXTEND, FLOAT_TRUNCATE, FLOAT, FIX, UNSIGNED_FLOAT,
>> + UNSIGNED_FIX, FRACT_CONVERT, UNSIGNED_FRACT_CONVERT, SAT_FRACT,
>> + UNSIGNED_SAT_FRACT, ABS, SQRT, BSWAP, FFS, CLZ, CTZ, POPCOUNT, PARITY,
>> + SIGN_EXTRACT, ZERO_EXTRACT, HIGH, LO_SUM, VEC_MERGE, VEC_SELECT,
>> + VEC_CONCAT, VEC_DUPLICATE, SS_PLUS, US_PLUS, SS_MINUS, SS_NEG, US_NEG,
>> + SS_ABS, SS_ASHIFT, US_ASHIFT, US_MINUS, SS_TRUNCATE, US_TRUNCATE, FMA,
>> + VAR_LOCATION, DEBUG_IMPLICIT_PTR, ENTRY_VALUE, LAST_AND_UNUSED_RTX_CODE
>> +};
>> +union rtunion_def
>> +{
>> + rtx rt_rtx;
>> +};
>> +typedef union rtunion_def rtunion;
>> +struct rtx_def
>> +{
>> + __extension__ enum rtx_code code:16;
>> + union u
>> + {
>> + rtunion fld[1];
>> + }
>> + u;
>> +};
>> +
>> +unsigned int rtx_cost (rtx, enum rtx_code, unsigned char);
>> +rtx single_set_2 (const_rtx, rtx);
>> +
>> +unsigned
>> +seq_cost (const_rtx seq, unsigned char speed)
>> +{
>> + unsigned cost = 0;
>> + rtx set;
>> + for (; seq; seq = (((seq)->u.fld[2]).rt_rtx))
>> + {
>> + set =
>> + (((((enum rtx_code) (seq)->code) == INSN)
>> + || (((enum rtx_code) (seq)->code) == DEBUG_INSN)
>> + || (((enum rtx_code) (seq)->code) == JUMP_INSN)
>> + || (((enum rtx_code) (seq)->code) ==
>> + CALL_INSN)) ? (((enum rtx_code) ((((seq)->u.fld[4]).rt_rtx))->
>> + code) ==
>> + SET ? (((seq)->u.fld[4]).
>> + rt_rtx) : single_set_2 (seq,
>> + (((seq)->u.
>> + fld[4]).
>> + rt_rtx))) :
>> (rtx)
>> + 0);
>> + if (set)
>> + cost += rtx_cost (set, SET, speed);
>> + }
>> +}
>> diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c
>> index 5be6ee4..9128094 100644
>> --- a/gcc/tree-ssa-threadbackward.c
>> +++ b/gcc/tree-ssa-threadbackward.c
>> @@ -211,10 +211,6 @@ fsm_find_control_statement_thread_paths (tree name,
>> continue;
>>
>> int path_length = path->length ();
>> - /* A path with less than 2 basic blocks should not be jump-threaded.
>> */
>> - if (path_length < 2)
>> - continue;
>> -
>> if (path_length > PARAM_VALUE (PARAM_MAX_FSM_THREAD_LENGTH))
>> {
>> if (dump_file && (dump_flags & TDF_DETAILS))
>>
