On Wed, Mar 4, 2015 at 12:09 PM, Alex Velenko wrote: > For example, in arm testcase pr43920-2.c, CSE previously decided not to put > an "obvious" note on insn 9, as set value was the same as note value. > At the same time, other insns set up as -1 were set up through a register > and did get a note:
...which is the point of the REG_EQUAL notes. In insn 8 there is a REG_EQUAL note to show that the value of r111 is known. In insn 9 the known value is, well, known from SET_SRC so there is no need for a REG_EQUAL note. Adding REG_EQUAL notes in such cases is just wasteful. > (insn 9 53 34 8 (set (reg:SI 110 [ D.4934 ]) > (const_int -1 [0xffffffffffffffff])) > /work/src/gcc/gcc/testsuite/gcc.target/arm/pr43920-2.c:21 613 > {*thumb2_movsi_vfp} > (nil)) > > (insn 8 45 50 6 (set (reg:SI 110 [ D.4934 ]) > (reg/v:SI 111 [ startD.4917 ])) > /work/src/gcc/gcc/testsuite/gcc.target/arm/pr43920-2.c:21 613 > {*thumb2_movsi_vfp} > (expr_list:REG_EQUAL (const_int -1 [0xffffffffffffffff]) > (nil))) > > (insn 6 49 54 7 (set (reg:SI 110 [ D.4934 ]) > (reg/v:SI 112 [ endD.4918 ])) > /work/src/gcc/gcc/testsuite/gcc.target/arm/pr43920-2.c:21 613 > {*thumb2_movsi_vfp} > (expr_list:REG_EQUAL (const_int -1 [0xffffffffffffffff]) > (nil))) > > Jump2 pass, optimizing common code, was looking at notes to reason about > register values and failing to recognize those insns to be equal. I suppose you are talking about the head/tail merging code? Can you please provide a test case for problem preferably filed in Bugzilla)? Ciao! Steven