on 2021/7/15 下午4:04, Kewen.Lin via Gcc-patches wrote: > Hi Uros, > > on 2021/7/15 下午3:17, Uros Bizjak wrote: >> On Thu, Jul 15, 2021 at 9:07 AM Kewen.Lin <li...@linux.ibm.com> wrote: >>> >>> on 2021/7/14 下午3:45, Kewen.Lin via Gcc-patches wrote: >>>> on 2021/7/14 下午2:38, Richard Biener wrote: >>>>> On Tue, Jul 13, 2021 at 4:59 PM Kewen.Lin <li...@linux.ibm.com> wrote: >>>>>> >>>>>> on 2021/7/13 下午8:42, Richard Biener wrote: >>>>>>> On Tue, Jul 13, 2021 at 12:25 PM Kewen.Lin <li...@linux.ibm.com> wrote: >>>>> >>>>>> I guess the proposed IFN would be directly mapped for [us]mul_highpart? >>>>> >>>>> Yes. >>>>> >>>> >>>> Thanks for confirming! The related patch v2 is attached and the testing >>>> is ongoing. >>>> >>> >>> It's bootstrapped & regtested on powerpc64le-linux-gnu P9 and >>> aarch64-linux-gnu. But on x86_64-redhat-linux there are XPASSes as below: >>> >>> XFAIL->XPASS: gcc.target/i386/pr100637-3w.c scan-assembler pmulhuw >>> XFAIL->XPASS: gcc.target/i386/pr100637-3w.c scan-assembler pmulhuw >>> XFAIL->XPASS: gcc.target/i386/pr100637-3w.c scan-assembler pmulhw >>> XFAIL->XPASS: gcc.target/i386/pr100637-3w.c scan-assembler pmulhw >> >> These XFAILs should be removed after your patch. >> > I'm curious whether it's intentional not to specify -fno-vect-cost-model > for this test case. As noted above, this case is sensitive on how we > cost mult_highpart. Without cost modeling, the XFAILs can be removed > only with this mul_highpart pattern support, no matter how we model it > (x86 part of this patch exists or not). > >> This is PR100696 [1], we want PMULH.W here, so x86 part of the patch >> is actually not needed. >> > > Thanks for the information! The justification for the x86 part is that: > the IFN_MULH essentially covers MULT_HIGHPART_EXPR with mul_highpart > optab support, i386 port has already customized costing for > MULT_HIGHPART_EXPR (should mean/involve the case with mul_highpart optab > support), if we don't follow the same way for IFN_MULH, I'm worried that > we may cost the IFN_MULH wrongly. If taking IFN_MULH as normal stmt is > a right thing (we shouldn't cost it specially), it at least means we > have to adjust ix86_multiplication_cost for MULT_HIGHPART_EXPR when it > has direct mul_highpart optab support, I think they should be costed > consistently. Does it sound reasonable? >
Hi Richard(s), This possibly inconsistent handling problem seems like a counter example better to use a new IFN rather than the existing tree_code, it seems hard to maintain (should remember to keep consistent for its handlings). ;) >From this perspective, maybe it's better to move backward to use tree_code and guard it under can_mult_highpart_p == 1 (just like IFN and avoid costing issue Richi pointed out before)? What do you think? BR, Kewen
