| Message ID | 87bmes6zt3.fsf@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | Set insn_last_address in final_1 | expand |
On Mon, Apr 9, 2018 at 7:43 PM, Richard Sandiford <richard.sandiford@linaro.org> wrote: > final_1 already sets insn_current_address for each instruction, making > it possible to use some of the address functions in final.c during > assembly generation. This patch also sets insn_last_address, since > as the comment says, we can treat final as a shorten_branches pass that > does nothing. It's then possible to use insn_current_reference_address > during final as well. > > This is needed for the aarch64.md definitions of far_branch to work: > > (set (attr "far_branch") > (if_then_else (and (ge (minus (match_dup 2) (pc)) (const_int -1048576)) > (lt (minus (match_dup 2) (pc)) (const_int 1048572))) > (const_int 0) > (const_int 1)))] > > This value (tested only during final) uses the difference between > the INSN_ADDRESSES of operand 2 and insn_current_reference_address > to calculate a conservatively-correct estimate of the branch distance. > It takes into account the worst-case gap due to alignment, whereas > a direct comparison of INSN_ADDRESSES would give an unreliable, > optimistic result. > > Tested on aarch64-linux-gnu and x86_64-linux-gnu. Sameera confirms > that it fixes the original bug, but there's no sharable testcase. > OK to install? OK. Richard. > Richard > > > 2018-04-09 Richard Sandiford <richard.sandiford@linaro.org> > > gcc/ > * final.c (final_1): Set insn_last_address as well as > insn_current_address. > > Index: gcc/final.c > =================================================================== > --- gcc/final.c 2018-04-09 18:40:26.887628387 +0100 > +++ gcc/final.c 2018-04-09 18:40:27.033624471 +0100 > @@ -2081,6 +2081,9 @@ final_1 (rtx_insn *first, FILE *file, in > } > else > insn_current_address = INSN_ADDRESSES (INSN_UID (insn)); > + /* final can be seen as an iteration of shorten_branches that > + does nothing (since a fixed point has already been reached). */ > + insn_last_address = insn_current_address; > } > > dump_basic_block_info (file, insn, start_to_bb, end_to_bb,
Index: gcc/final.c =================================================================== --- gcc/final.c 2018-04-09 18:40:26.887628387 +0100 +++ gcc/final.c 2018-04-09 18:40:27.033624471 +0100 @@ -2081,6 +2081,9 @@ final_1 (rtx_insn *first, FILE *file, in } else insn_current_address = INSN_ADDRESSES (INSN_UID (insn)); + /* final can be seen as an iteration of shorten_branches that + does nothing (since a fixed point has already been reached). */ + insn_last_address = insn_current_address; } dump_basic_block_info (file, insn, start_to_bb, end_to_bb,