From 040939a2387eff082f1594fac35f007f93d2dcd8 Mon Sep 17 00:00:00 2001 From: Kyrylo Tkachov Date: Wed, 8 Nov 2017 18:29:38 +0000 Subject: [PATCH] [simplify-rtx] Simplify vec_merge of vec_duplicates into vec_concat Another vec_merge simplification that's missing from simplify-rtx.c is transforming a vec_merge of two vec_duplicates. For example: (set (reg:V2DF 80) (vec_merge:V2DF (vec_duplicate:V2DF (reg:DF 84)) (vec_duplicate:V2DF (reg:DF 81)) (const_int 2))) Can be transformed into the simpler: (set (reg:V2DF 80) (vec_concat:V2DF (reg:DF 81) (reg:DF 84))) I believe this should always be beneficial. I'm still looking into finding a small testcase demonstrating this, but on aarch64 SPEC I've seen this eliminate some really bizzare codegen where GCC was generating nonsense like: ldr q18, [sp, 448] ins v18.d[0], v23.d[0] ins v18.d[1], v22.d[0] With q18 being pushed and popped off the stack in the prologue and epilogue of the function! These are large files from SPEC that I haven't been able to analyse yet as to why GCC even attempts to do that, but with this patch it doesn't try to load a register and overwrite all its lanes. This patch shaves off about 5k of code size from zeusmp on aarch64 at -O3, so I believe it's a good thing to do. * simplify-rtx.c (simplify_ternary_operation): Simplify vec_merge of two vec_duplicates into a vec_concat. From-SVN: r254550 --- gcc/ChangeLog | 5 +++++ gcc/simplify-rtx.c | 18 ++++++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 9b50bca8151..37ccb2cbd0e 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2017-11-08 Kyrylo Tkachov + + * simplify-rtx.c (simplify_ternary_operation): Simplify vec_merge + of two vec_duplicates into a vec_concat. + 2017-11-08 Kyrylo Tkachov * simplify-rtx.c (simplify_ternary_operation, VEC_MERGE): diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index 92c783af5a6..e1a16a46a4c 100644 --- a/gcc/simplify-rtx.c +++ b/gcc/simplify-rtx.c @@ -5784,6 +5784,24 @@ simplify_ternary_operation (enum rtx_code code, machine_mode mode, if (!side_effects_p (otherop)) return simplify_gen_binary (VEC_CONCAT, mode, newop0, newop1); } + + /* Replace (vec_merge (vec_duplicate x) (vec_duplicate y) + (const_int n)) + with (vec_concat x y) or (vec_concat y x) depending on value + of N. */ + if (GET_CODE (op0) == VEC_DUPLICATE + && GET_CODE (op1) == VEC_DUPLICATE + && GET_MODE_NUNITS (GET_MODE (op0)) == 2 + && GET_MODE_NUNITS (GET_MODE (op1)) == 2 + && IN_RANGE (sel, 1, 2)) + { + rtx newop0 = XEXP (op0, 0); + rtx newop1 = XEXP (op1, 0); + if (sel == 2) + std::swap (newop0, newop1); + + return simplify_gen_binary (VEC_CONCAT, mode, newop0, newop1); + } } if (rtx_equal_p (op0, op1) -- 2.30.2