Hi! (I have no idea why this PR is a P1).
On Tue, Mar 31, 2020 at 09:04:18AM +0200, Jakub Jelinek wrote: > The following testcase ICEs on armv7hl-linux-gnueabi. Also on default arm-linux-gnueabi. It needs -Og. > try_combine is called on: > (gdb) p debug_rtx (i3) > (insn 20 12 22 2 (set (mem/c:SI (plus:SI (reg/f:SI 102 sfp) > (const_int -4 [0xfffffffffffffffc])) [1 x+0 S4 A32]) > (reg:SI 125)) "pr94291.c":7:8 241 {*arm_movsi_insn} > (expr_list:REG_DEAD (reg:SI 125) > (nil))) > (gdb) p debug_rtx (i2) > (insn 12 7 20 2 (parallel [ > (set (reg:CC 100 cc) > (compare:CC (reg:SI 121 [ <retval> ]) > (const_int 0 [0]))) > (set (reg:SI 125) > (reg:SI 121 [ <retval> ])) > ]) "pr94291.c":7:8 248 {*movsi_compare0} > (expr_list:REG_UNUSED (reg:CC 100 cc) > (nil))) > and tries to recognize cc = r121 cmp 0; [sfp-4] = r121 parallel, > but that isn't recognized, Trying 12 -> 20: 12: {cc:CC=cmp(r118:SI,0);r122:SI=r118:SI;} REG_UNUSED cc:CC 20: [sfp:SI-0x4]=r122:SI REG_DEAD r122:SI Failed to match this instruction: (parallel [ (set (reg:CC 100 cc) (compare:CC (reg:SI 118 [ <retval> ]) (const_int 0 [0]))) (set (mem/c:SI (plus:SI (reg/f:SI 102 sfp) (const_int -4 [0xfffffffffffffffc])) [1 x+0 S4 A32]) (reg:SI 118 [ <retval> ])) ]) (twice) > so it splits it into two: split_i2i3 (That variable does not *control* the splitting: it registers that we did split a parallel into newi2pat and newpat). Successfully matched this instruction: (set (mem/c:SI (plus:SI (reg/f:SI 102 sfp) (const_int -4 [0xfffffffffffffffc])) [1 x+0 S4 A32]) (reg:SI 118 [ <retval> ])) Successfully matched this instruction: (set (reg:CC 100 cc) (compare:CC (reg:SI 118 [ <retval> ]) (const_int 0 [0]))) allowing combination of insns 12 and 20 original costs 4 + 4 = 8 replacement costs 4 + 4 = 8 > [sfp-4] = r121 followed by cc = r121 cmp 0 which is recognized, but > ICEs because the code below insist that the SET_DEST of newi2pat > (or first set in PARALLEL thereof) must be a REG or SUBREG of REG, > but it is a MEM in this case. I don't see any condition that would > guarantee that, perhaps for the swap_i2i3 case it was somehow guaranteed. I don't see how it was guaranteed for that case, either. > As the code just wants to update LOG_LINKS and LOG_LINKS are only for > registers, not for MEM or anything else, the patch just doesn't update those > if it isn't a REG or SUBREG of REG. That is correct. > 2020-03-31 Jakub Jelinek <ja...@redhat.com> > > PR rtl-optimization/94291 Please mention PR rtl-optimization/84169 as well. > * combine.c (try_combine): For split_i2i3, don't assume SET_DEST > must be a REG or SUBREG of REG; if it is not one of these, don't > update LOG_LINKs. > > * gcc.dg/pr94291.c: New test. Okay for trunk, and for backports as well (after soaking it for a bit). Thanks! Segher