https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24021
--- Comment #26 from Aldy Hernandez <aldyh at gcc dot gnu.org> --- (In reply to Andrew Macleod from comment #19) > We can use the original testcase as the litmus test for basic support if we > compile it with > > -O2 -fno-tree-fre -fno-tree-dominator-opts > > The unroller will unroll the loop and the VRP2 pass will be presented with: > > <bb 2> [local count: 97603129]: > i_1 = 1.1000000149011611438876201418679556809365749359130859375e-1; > i_17 = i_1 + 1.00000001490116119384765625e-1; > i_22 = i_17 + 1.00000001490116119384765625e-1; > i_27 = i_22 + 1.00000001490116119384765625e-1; > i_32 = i_27 + 1.00000001490116119384765625e-1; > i_37 = i_32 + 1.00000001490116119384765625e-1; > i_42 = i_37 + 1.00000001490116119384765625e-1; > i_47 = i_42 + 1.00000001490116119384765625e-1; > i_52 = i_47 + 1.00000001490116119384765625e-1; > if (i_52 == 0.0) > goto <bb 4>; [50.00%] > else > goto <bb 3>; [50.00%] > > <bb 3> [local count: 48801565]: > > <bb 4> [local count: 97603129]: > # lastPoint_12 = PHI <i_52(2), 2.0e+0(3)> > return lastPoint_12; > > Which is we can track floating point ranges in VRP and simplification, > recognize that i_52 != 0.0 and VRP2 should be able to resolve this to > > return 2.0e+0; Errr, just saw this. I if we let the unroller do it's thing, we can catch this at VRP2, and continue using this testcase. And sure enough, my current work catches this: Folding statement: i_5 = 1.1000000149011611438876201418679556809365749359130859375e-1; Queued stmt for removal. Folds to: 1.1000000149011611438876201418679556809365749359130859375e-1 Folding statement: i_17 = i_5 + 1.00000001490116119384765625e-1; Queued stmt for removal. Folds to: 2.100000029802322476513154470012523233890533447265625e-1 ... ... ... Folding statement: if (i_52 == 0.0) gimple_simplified to if (0 != 0) gimple_simplified to if (0 != 0) Folded into: if (0 != 0)
