Re: [PATCH 1/3] [ARM] Add bus_width_bits to tune_params

Wed, 13 Sep 2017 02:03:08 -0700 

Hi Charles,

On 12/09/17 09:34, charles.bay...@linaro.org wrote:

From: Charles Baylis <charles.bay...@linaro.org>

Add bus widths. These use the approximation that v7 and later cores have
64bit data bus width, and earlier cores have 32 bit bus width, with the
exception of v7m.
Given the way this field is used in patch 2 does it affect the addressing mode generation 
in the tests you added depending on the -mtune option given?
If so, we'll get testsuite failures when people test with particular default CPU configurations.
Could you expand on the benefits we get from this extra bus_width information? I get that we increase the cost of memory accesses if the size of the mode we load is larger than the bus width, but it's not as if there is ever an alternative in this regard, such as loading less memory, 
so what pass can make different decisions thanks to this field?

Thanks,
Kyrill


<date>  Charles Baylis <charles.bay...@linaro.org>

        * config/arm/arm-protos.h (struct tune_params): New field
        bus_width.
        * config/arm/arm.c (arm_slowmul_tune): Initialise bus_width field.
        (arm_fastmul_tune): Likewise.
        (arm_strongarm_tune): Likewise.
        (arm_xscale_tune): Likewise.
        (arm_9e_tune): Likewise.
        (arm_marvell_pj4_tune): Likewise.
        (arm_v6t2_tune): Likewise.
        (arm_cortex_tune): Likewise.
        (arm_cortex_a8_tune): Likewise.
        (arm_cortex_a7_tune): Likewise.
        (arm_cortex_a15_tune): Likewise.
        (arm_cortex_a35_tune): Likewise.
        (arm_cortex_a53_tune): Likewise.
        (arm_cortex_a57_tune): Likewise.
        (arm_exynosm1_tune): Likewise.
        (arm_xgene1_tune): Likewise.
        (arm_cortex_a5_tune): Likewise.
        (arm_cortex_a9_tune): Likewise.
        (arm_cortex_a12_tune): Likewise.
        (arm_cortex_a73_tune): Likewise.
        (arm_v7m_tune): Likewise.
        (arm_cortex_m7_tune): Likewise.
        (arm_v6m_tune): Likewise.
        (arm_fa726te_tune): Likewise.

Change-Id: I613e876db93ffd6f8c1e72ba483be2efc0b56d66
---
 gcc/config/arm/arm-protos.h |  2 ++
 gcc/config/arm/arm.c        | 24 ++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/gcc/config/arm/arm-protos.h b/gcc/config/arm/arm-protos.h
index 4538078..47a85cc 100644
--- a/gcc/config/arm/arm-protos.h
+++ b/gcc/config/arm/arm-protos.h
@@ -278,6 +278,8 @@ struct tune_params
   int max_insns_inline_memset;
   /* Issue rate of the processor.  */
   unsigned int issue_rate;
+  /* Bus width (bits).  */
+  unsigned int bus_width;
   /* Explicit prefetch data.  */
   struct
     {
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index bca8a34..32001e5 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -1761,6 +1761,7 @@ const struct tune_params arm_slowmul_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   1,                                           /* Issue rate.  */
+  32,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_TRUE,
   tune_params::PREF_LDRD_FALSE,
@@ -1783,6 +1784,7 @@ const struct tune_params arm_fastmul_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   1,                                           /* Issue rate.  */
+  32,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_TRUE,
   tune_params::PREF_LDRD_FALSE,
@@ -1808,6 +1810,7 @@ const struct tune_params arm_strongarm_tune =
   3,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   1,                                           /* Issue rate.  */
+  32,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_TRUE,
   tune_params::PREF_LDRD_FALSE,
@@ -1830,6 +1833,7 @@ const struct tune_params arm_xscale_tune =
   3,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   1,                                           /* Issue rate.  */
+  32,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_TRUE,
   tune_params::PREF_LDRD_FALSE,
@@ -1852,6 +1856,7 @@ const struct tune_params arm_9e_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   1,                                           /* Issue rate.  */
+  32,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_TRUE,
   tune_params::PREF_LDRD_FALSE,
@@ -1874,6 +1879,7 @@ const struct tune_params arm_marvell_pj4_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  32,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_TRUE,
   tune_params::PREF_LDRD_FALSE,
@@ -1896,6 +1902,7 @@ const struct tune_params arm_v6t2_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   1,                                           /* Issue rate.  */
+  32,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_FALSE,
@@ -1920,6 +1927,7 @@ const struct tune_params arm_cortex_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_FALSE,
@@ -1942,6 +1950,7 @@ const struct tune_params arm_cortex_a8_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_FALSE,
@@ -1964,6 +1973,7 @@ const struct tune_params arm_cortex_a7_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_FALSE,
@@ -1986,6 +1996,7 @@ const struct tune_params arm_cortex_a15_tune =
   2,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   3,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_TRUE,
@@ -2008,6 +2019,7 @@ const struct tune_params arm_cortex_a35_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   1,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_FALSE,
@@ -2030,6 +2042,7 @@ const struct tune_params arm_cortex_a53_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_FALSE,
@@ -2052,6 +2065,7 @@ const struct tune_params arm_cortex_a57_tune =
   2,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   3,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_TRUE,
@@ -2074,6 +2088,7 @@ const struct tune_params arm_exynosm1_tune =
   2,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   3,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_TRUE,
@@ -2096,6 +2111,7 @@ const struct tune_params arm_xgene1_tune =
   2,                                           /* Max cond insns.  */
   32,                                          /* Memset max inline.  */
   4,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_TRUE,
@@ -2121,6 +2137,7 @@ const struct tune_params arm_cortex_a5_tune =
   1,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_FALSE,
@@ -2143,6 +2160,7 @@ const struct tune_params arm_cortex_a9_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_BENEFICIAL(4,32,32),
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_FALSE,
@@ -2165,6 +2183,7 @@ const struct tune_params arm_cortex_a12_tune =
   2,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_TRUE,
@@ -2187,6 +2206,7 @@ const struct tune_params arm_cortex_a73_tune =
   2,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_TRUE,
@@ -2216,6 +2236,7 @@ const struct tune_params arm_v7m_tune =
   2,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   1,                                           /* Issue rate.  */
+  32,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_TRUE,
   tune_params::PREF_LDRD_FALSE,
@@ -2240,6 +2261,7 @@ const struct tune_params arm_cortex_m7_tune =
   1,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  64,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_TRUE,
   tune_params::PREF_LDRD_FALSE,
@@ -2265,6 +2287,7 @@ const struct tune_params arm_v6m_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   1,                                           /* Issue rate.  */
+  32,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_FALSE,
   tune_params::PREF_LDRD_FALSE,
@@ -2287,6 +2310,7 @@ const struct tune_params arm_fa726te_tune =
   5,                                           /* Max cond insns.  */
   8,                                           /* Memset max inline.  */
   2,                                           /* Issue rate.  */
+  32,                                          /* Bus width.  */
   ARM_PREFETCH_NOT_BENEFICIAL,
   tune_params::PREF_CONST_POOL_TRUE,
   tune_params::PREF_LDRD_FALSE,
--
2.7.4

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