Hi,
Richard Biener <rguent...@suse.de> writes: > On Mon, 12 Jun 2023, Jiufu Guo wrote: > >> Richard Biener <rguent...@suse.de> writes: >> >> > On Fri, 9 Jun 2023, Jiufu Guo wrote: >> > >> >> >> >> Hi, >> >> >> >> Richard Biener <rguent...@suse.de> writes: >> >> >> >> > On Fri, 9 Jun 2023, Jiufu Guo wrote: >> >> > >> >> >> >> >> >> Hi, >> >> >> >> >> >> Richard Biener <rguent...@suse.de> writes: >> >> >> >> >> >> > On Fri, 9 Jun 2023, Richard Sandiford wrote: >> >> >> > >> >> >> >> guojiufu <guoji...@linux.ibm.com> writes: >> >> >> >> > Hi, >> >> >> >> > >> >> >> >> > On 2023-06-09 16:00, Richard Biener wrote: >> >> >> >> >> On Fri, 9 Jun 2023, Jiufu Guo wrote: >> >> >> >> >> >> >> >> >> >>> Hi, >> >> >> >> >>> >> >> ... >> >> >> >> >>> >> >> >> >> >>> This patch is raised when drafting below one. >> >> >> >> >>> https://gcc.gnu.org/pipermail/gcc-patches/2022-October/603530.html. >> >> >> >> >>> With that patch, "{[%1:DI]=0;} stack_tie" with BLKmode runs into >> >> >> >> >>> try_const_anchors, and hits the assert/ice. >> >> >> >> >>> >> >> >> >> >>> Boostrap and regtest pass on ppc64{,le} and x86_64. >> >> >> >> >>> Is this ok for trunk? >> >> >> >> >> >> >> >> >> >> Iff the correct fix at all (how can a CONST_INT have BLKmode?) >> >> >> >> >> then >> >> >> >> >> I suggest to instead fix try_const_anchors to change >> >> >> >> >> >> >> >> >> >> /* CONST_INT is used for CC modes, but we should leave those >> >> >> >> >> alone. >> >> >> >> >> */ >> >> >> >> >> if (GET_MODE_CLASS (mode) == MODE_CC) >> >> >> >> >> return NULL_RTX; >> >> >> >> >> >> >> >> >> >> gcc_assert (SCALAR_INT_MODE_P (mode)); >> >> >> >> >> >> >> >> >> >> to >> >> >> >> >> >> >> >> >> >> /* CONST_INT is used for CC modes, leave any non-scalar-int >> >> >> >> >> mode >> >> >> >> >> alone. */ >> >> >> >> >> if (!SCALAR_INT_MODE_P (mode)) >> >> >> >> >> return NULL_RTX; >> >> >> >> >> >> >> >> >> > >> >> >> >> > This is also able to fix this issue. there is a "Punt on CC >> >> >> >> > modes" >> >> >> >> > patch >> >> >> >> > to return NULL_RTX in try_const_anchors. >> >> >> >> > >> >> >> >> >> but as said I wonder how we arrive at a BLKmode CONST_INT and >> >> >> >> >> whether >> >> >> >> >> we should have fended this off earlier. Can you share more >> >> >> >> >> complete >> >> >> >> >> RTL of that stack_tie? >> >> >> >> > >> >> >> >> > >> >> >> >> > (insn 15 14 16 3 (parallel [ >> >> >> >> > (set (mem/c:BLK (reg/f:DI 1 1) [1 A8]) >> >> >> >> > (const_int 0 [0])) >> >> >> >> > ]) "/home/guojiufu/temp/gdb.c":13:3 922 {stack_tie} >> >> >> >> > (nil)) >> >> >> >> > >> >> >> >> > It is "set (mem/c:BLK (reg/f:DI 1 1) (const_int 0 [0])". >> >> >> >> >> >> >> >> I'm not convinced this is correct RTL. (unspec:BLK [(const_int 0)] >> >> >> >> ...) >> >> >> >> would be though. It's arguably more accurate too, since the effect >> >> >> >> on the stack locations is unspecified rather than predictable. >> >> >> > >> >> >> > powerpc seems to be the only port with a stack_tie that's not >> >> >> > using an UNSPEC RHS. >> >> >> In rs6000.md, it is >> >> >> >> >> >> ; This is to explain that changes to the stack pointer should >> >> >> ; not be moved over loads from or stores to stack memory. >> >> >> (define_insn "stack_tie" >> >> >> [(match_parallel 0 "tie_operand" >> >> >> [(set (mem:BLK (reg 1)) (const_int 0))])] >> >> >> "" >> >> >> "" >> >> >> [(set_attr "length" "0")]) >> >> >> >> >> >> This would be just an placeholder insn, and acts as the comments. >> >> >> UNSPEC_ would works like other targets. While, I'm wondering >> >> >> the concerns on "set (mem:BLK (reg 1)) (const_int 0)". >> >> >> MODEs between SET_DEST and SET_SRC? >> >> > >> >> > I don't think the issue is the mode but the issue is that >> >> > the patter as-is says some memory is zeroed while that's not >> >> > actually true (not specifying a size means we can't really do >> >> > anything with this MEM, but still). Using an UNSPEC avoids >> >> > implying anything for the stored value. >> >> > >> >> > Of course I think a MEM SET_DEST without a specified size is bougs >> >> > as well, but there's larger precedent for this... >> >> >> >> Thanks for your kindly comments! >> >> Using "(set (mem:BLK (reg 1)) (const_int 0))" here, may because this >> >> insn does not generate real thing (not a real store and no asm code), >> >> may like barrier. >> >> >> >> While I agree that, using UNSPEC may be more clear to avoid mis-reading. >> > >> > Btw, another way to avoid the issue in CSE is to make it not process >> > (aka record anything for optimization) for SET from MEMs with >> > !MEM_SIZE_KNOWN_P >> >> Thanks! Yes, this would make sense. >> Then, there are two ideas(patches) to handle this issue: >> Which one would be preferable? This one (from compiling time aspect)? >> >> And maybe, the changes in rs6000 stack_tie through using unspec >> can be a standalone enhancement besides cse patch. >> >> Thanks for comments! >> >> BR, >> Jeff (Jiufu Guo) >> >> -------------------- patch 1 >> diff --git a/gcc/cse.cc b/gcc/cse.cc >> index 2bb63ac4105..06ecdadecbc 100644 >> --- a/gcc/cse.cc >> +++ b/gcc/cse.cc >> @@ -4271,6 +4271,8 @@ find_sets_in_insn (rtx_insn *insn, vec<struct set> >> *psets) >> someplace else, so it isn't worth cse'ing. */ >> else if (GET_CODE (SET_SRC (x)) == CALL) >> ; >> + else if (MEM_P (SET_DEST (x)) && !MEM_SIZE_KNOWN_P (SET_DEST (x))) >> + ; > > I don't know CSE enough to decide if this is correct, it depends on > whether pset is only used to record new sets or if it is also used > to invalidate prior recorded sets (in which case these sets have to > be recorded still). That is, the fix might better be in the caller > who interprets 'pset' The 'sets' is a variable of cse_insn: "auto_vec<struct set, 8> sets;" And the cse work in cse_insn is based on this 'sets'. So if a 'set' is not added to this 'sets' through 'find_sets_in_insn', it would be skipped from the cse process. So, this patch updates 'find_sets_in_insn' to avoid adding the 'set' with 'unknown mem size' to the 'sets'. I'm not get the meaning of "the fix might better be in the caller who interprets 'pset'". Thanks a lot for your comments! BR, Jeff (Jiufu Guo) > >> else if (GET_CODE (SET_SRC (x)) == CONST_VECTOR >> && GET_MODE_CLASS (GET_MODE (SET_SRC (x))) != MODE_VECTOR_BOOL >> /* Prevent duplicates from being generated if the type is a V1 >> @@ -4314,6 +4316,8 @@ find_sets_in_insn (rtx_insn *insn, vec<struct set> >> *psets) >> ; >> else if (GET_CODE (SET_SRC (y)) == CALL) >> ; >> + else if (MEM_P (SET_DEST (y)) && !MEM_SIZE_KNOWN_P (SET_DEST (y))) >> + ; >> else >> add_to_set (psets, y); >> } >> ----------------------------- >> -------------------patch 2 >> diff --git a/gcc/cse.cc b/gcc/cse.cc >> index 2bb63ac4105..ddb76fd281d 100644 >> --- a/gcc/cse.cc >> +++ b/gcc/cse.cc >> @@ -1312,11 +1312,10 @@ try_const_anchors (rtx src_const, machine_mode mode) >> rtx lower_exp = NULL_RTX, upper_exp = NULL_RTX; >> unsigned lower_old, upper_old; >> >> - /* CONST_INT is used for CC modes, but we should leave those alone. */ >> - if (GET_MODE_CLASS (mode) == MODE_CC) >> + /* CONST_INT is used for CC/BLK modes, leave any non-scalar-int mode >> alone. */ >> + if (!SCALAR_INT_MODE_P (mode)) >> return NULL_RTX; >> >> - gcc_assert (SCALAR_INT_MODE_P (mode)); >> if (!compute_const_anchors (src_const, &lower_base, &lower_offs, >> &upper_base, &upper_offs)) >> return NULL_RTX; >> ------------- >> >> >> BR, >> Jeff (Jiufu Guo) >> > >> > Richard. >>
