From 87b44b83c0aab29fac51f510288032690a6e2886 Mon Sep 17 00:00:00 2001 From: Aaron Sawdey Date: Mon, 10 Oct 2016 04:42:08 +0000 Subject: [PATCH] rs6000.h (TARGET_EFFICIENT_OVERLAPPING_UNALIGNED): Add macro to say we can efficiently handle overlapping unaligned loads. 2016-10-09 Aaron Sawdey * config/rs6000/rs6000.h (TARGET_EFFICIENT_OVERLAPPING_UNALIGNED): Add macro to say we can efficiently handle overlapping unaligned loads. * config/rs6000/rs6000.c (expand_block_compare): Avoid generating poor code for processors older than p8. From-SVN: r240908 --- gcc/ChangeLog | 8 ++++++++ gcc/config/rs6000/rs6000.c | 26 ++++++++++++++++++++++---- gcc/config/rs6000/rs6000.h | 3 +++ 3 files changed, 33 insertions(+), 4 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index a6c2fcdbef3..7842655c79a 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2016-10-09 Aaron Sawdey + + * config/rs6000/rs6000.h (TARGET_EFFICIENT_OVERLAPPING_UNALIGNED): + Add macro to say we can efficiently handle overlapping unaligned + loads. + * config/rs6000/rs6000.c (expand_block_compare): Avoid generating + poor code for processors older than p8. + 2016-10-09 Eric Botcazou * gen-pass-instances.awk: Remove GNUism. diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c index 49da4b629ae..8c7ab18224b 100644 --- a/gcc/config/rs6000/rs6000.c +++ b/gcc/config/rs6000/rs6000.c @@ -18771,6 +18771,14 @@ expand_block_compare (rtx operands[]) if (bytes <= 0) return true; + /* The code generated for p7 and older is not faster than glibc + memcmp if alignment is small and length is not short, so bail + out to avoid those conditions. */ + if (!TARGET_EFFICIENT_OVERLAPPING_UNALIGNED + && ((base_align == 1 && bytes > 16) + || (base_align == 2 && bytes > 32))) + return false; + rtx tmp_reg_src1 = gen_reg_rtx (word_mode); rtx tmp_reg_src2 = gen_reg_rtx (word_mode); @@ -18820,13 +18828,18 @@ expand_block_compare (rtx operands[]) while (bytes > 0) { int align = compute_current_alignment (base_align, offset); - load_mode = select_block_compare_mode(offset, bytes, align, word_mode_ok); + if (TARGET_EFFICIENT_OVERLAPPING_UNALIGNED) + load_mode = select_block_compare_mode (offset, bytes, align, + word_mode_ok); + else + load_mode = select_block_compare_mode (0, bytes, align, word_mode_ok); load_mode_size = GET_MODE_SIZE (load_mode); if (bytes >= load_mode_size) cmp_bytes = load_mode_size; - else + else if (TARGET_EFFICIENT_OVERLAPPING_UNALIGNED) { - /* Move this load back so it doesn't go past the end. */ + /* Move this load back so it doesn't go past the end. + P8/P9 can do this efficiently. */ int extra_bytes = load_mode_size - bytes; cmp_bytes = bytes; if (extra_bytes < offset) @@ -18836,7 +18849,12 @@ expand_block_compare (rtx operands[]) bytes = cmp_bytes; } } - + else + /* P7 and earlier can't do the overlapping load trick fast, + so this forces a non-overlapping load and a shift to get + rid of the extra bytes. */ + cmp_bytes = bytes; + src1 = adjust_address (orig_src1, load_mode, offset); src2 = adjust_address (orig_src2, load_mode, offset); diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h index ad5819385fe..f53da155160 100644 --- a/gcc/config/rs6000/rs6000.h +++ b/gcc/config/rs6000/rs6000.h @@ -607,6 +607,9 @@ extern int rs6000_vector_align[]; && TARGET_POWERPC64) #define TARGET_VEXTRACTUB (TARGET_P9_VECTOR && TARGET_DIRECT_MOVE \ && TARGET_UPPER_REGS_DI && TARGET_POWERPC64) +/* This wants to be set for p8 and newer. On p7, overlapping unaligned + loads are slow. */ +#define TARGET_EFFICIENT_OVERLAPPING_UNALIGNED TARGET_EFFICIENT_UNALIGNED_VSX /* Byte/char syncs were added as phased in for ISA 2.06B, but are not present in power7, so conditionalize them on p8 features. TImode syncs need quad -- 2.30.2