From ecc82a8d0551e02afc9bb4d9dff450f6f0098b4e Mon Sep 17 00:00:00 2001 From: Andrew Waterman Date: Sun, 5 Nov 2017 00:30:40 +0000 Subject: [PATCH] RISC-V: Set SLOW_BYTE_ACCESS=1 When implementing the RISC-V port, I took the name of this macro at face value. It appears we were mistaken in what this means, here's a quote from the SPARC port that better describes what SLOW_BYTE_ACCESS does /* Nonzero if access to memory by bytes is slow and undesirable. For RISC chips, it means that access to memory by bytes is no better than access by words when possible, so grab a whole word and maybe make use of that. */ I've added the comment to our port as well. See https://gcc.gnu.org/ml/gcc/2017-08/msg00202.html for more discussion. Thanks to Michael Clark and Andrew Pinski for the help! gcc/ChangeLog 2017-11-04 Andrew Waterman * config/riscv/riscv.h (SLOW_BYTE_ACCESS): Change to 1. From-SVN: r254416 --- gcc/ChangeLog | 4 ++++ gcc/config/riscv/riscv.h | 7 ++++++- 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index ec8af50fa05..285ac2014df 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,7 @@ +2017-11-04 Andrew Waterman + + * config/riscv/riscv.h (SLOW_BYTE_ACCESS): Change to 1. + 2017-11-04 Daniel Santos config/i386/i386.c (choose_basereg): Use optional scratch diff --git a/gcc/config/riscv/riscv.h b/gcc/config/riscv/riscv.h index e53555efe82..a802a3f8cbb 100644 --- a/gcc/config/riscv/riscv.h +++ b/gcc/config/riscv/riscv.h @@ -615,7 +615,12 @@ typedef struct { #define MOVE_MAX UNITS_PER_WORD #define MAX_MOVE_MAX 8 -#define SLOW_BYTE_ACCESS 0 +/* The SPARC port says: + Nonzero if access to memory by bytes is slow and undesirable. + For RISC chips, it means that access to memory by bytes is no + better than access by words when possible, so grab a whole word + and maybe make use of that. */ +#define SLOW_BYTE_ACCESS 1 #define SHIFT_COUNT_TRUNCATED 1 -- 2.30.2