From: Jiong Wang Date: Mon, 25 Jul 2016 13:36:33 +0000 (+0000) Subject: [AArch64][2/3] Optimize aarch64_add_constant to generate better addition sequences X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=c4ddc43acce4417495d3ff3c194edfc2184ecb4f;p=gcc.git [AArch64][2/3] Optimize aarch64_add_constant to generate better addition sequences gcc/ * config/aarch64/aarch64.c (aarch64_add_constant): Optimize instruction sequences. From-SVN: r238713 --- diff --git a/gcc/ChangeLog b/gcc/ChangeLog index aa8cc14c020..a2550d118b1 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2016-07-25 Jiong Wang + + * config/aarch64/aarch64.c (aarch64_add_constant): Optimize instruction + sequences. + 2016-07-25 Jiong Wang * config/aarch64/aarch64.c (aarch64_add_constant): New parameter "mode". diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c index 92c4ae4777a..6cecb8fc47f 100644 --- a/gcc/config/aarch64/aarch64.c +++ b/gcc/config/aarch64/aarch64.c @@ -1940,6 +1940,47 @@ aarch64_expand_mov_immediate (rtx dest, rtx imm) aarch64_internal_mov_immediate (dest, imm, true, GET_MODE (dest)); } +/* Add DELTA to REGNUM in mode MODE. SCRATCHREG can be used to held + intermediate value if necessary. */ + +static void +aarch64_add_constant (machine_mode mode, int regnum, int scratchreg, + HOST_WIDE_INT delta) +{ + HOST_WIDE_INT mdelta = abs_hwi (delta); + rtx this_rtx = gen_rtx_REG (mode, regnum); + + /* Do nothing if mdelta is zero. */ + if (!mdelta) + return; + + /* We only need single instruction if the offset fit into add/sub. */ + if (aarch64_uimm12_shift (mdelta)) + { + emit_insn (gen_add2_insn (this_rtx, GEN_INT (delta))); + return; + } + + /* We need two add/sub instructions, each one performing part of the + calculation. Don't do this if the addend can be loaded into register with + a single instruction, in that case we prefer a move to a scratch register + following by an addition. */ + if (mdelta < 0x1000000 && !aarch64_move_imm (delta, mode)) + { + HOST_WIDE_INT low_off = mdelta & 0xfff; + + low_off = delta < 0 ? -low_off : low_off; + emit_insn (gen_add2_insn (this_rtx, GEN_INT (low_off))); + emit_insn (gen_add2_insn (this_rtx, GEN_INT (delta - low_off))); + return; + } + + /* Otherwise use generic function to handle all other situations. */ + rtx scratch_rtx = gen_rtx_REG (mode, scratchreg); + aarch64_internal_mov_immediate (scratch_rtx, GEN_INT (delta), true, mode); + emit_insn (gen_add2_insn (this_rtx, scratch_rtx)); +} + static bool aarch64_function_ok_for_sibcall (tree decl ATTRIBUTE_UNUSED, tree exp ATTRIBUTE_UNUSED) @@ -3412,44 +3453,6 @@ aarch64_final_eh_return_addr (void) - 2 * UNITS_PER_WORD)); } -static void -aarch64_add_constant (machine_mode mode, int regnum, int scratchreg, - HOST_WIDE_INT delta) -{ - HOST_WIDE_INT mdelta = delta; - rtx this_rtx = gen_rtx_REG (mode, regnum); - rtx scratch_rtx = gen_rtx_REG (mode, scratchreg); - - if (mdelta < 0) - mdelta = -mdelta; - - if (mdelta >= 4096 * 4096) - { - aarch64_internal_mov_immediate (scratch_rtx, GEN_INT (delta), true, mode); - emit_insn (gen_add3_insn (this_rtx, this_rtx, scratch_rtx)); - } - else if (mdelta > 0) - { - if (mdelta >= 4096) - { - emit_insn (gen_rtx_SET (scratch_rtx, GEN_INT (mdelta / 4096))); - rtx shift = gen_rtx_ASHIFT (mode, scratch_rtx, GEN_INT (12)); - if (delta < 0) - emit_insn (gen_rtx_SET (this_rtx, - gen_rtx_MINUS (mode, this_rtx, shift))); - else - emit_insn (gen_rtx_SET (this_rtx, - gen_rtx_PLUS (mode, this_rtx, shift))); - } - if (mdelta % 4096 != 0) - { - scratch_rtx = GEN_INT ((delta < 0 ? -1 : 1) * (mdelta % 4096)); - emit_insn (gen_rtx_SET (this_rtx, - gen_rtx_PLUS (mode, this_rtx, scratch_rtx))); - } - } -} - /* Output code to add DELTA to the first argument, and then jump to FUNCTION. Used for C++ multiple inheritance. */ static void