From 9b9c65b968fa2a1e6c2f86275e03f0ad96995b55 Mon Sep 17 00:00:00 2001
From: Lionel Debroux <lionel_debroux@yahoo.fr>
Date: Wed, 29 Nov 2023 12:45:17 +0100
Subject: [PATCH] Reduce padding and relocations (#355)

* Optimize the JEP106 list by using __attribute__((packed)) to remove padding. The x86 & x86_64 series support unaligned accesses just fine, after all, and this is not remotely a hot path.

* Optimize several string-related constructs by switching to fixed-length char arrays, which avoids pointers + relocations.

* app/interrupt.c: array of different-length strings, but most of those are lengthy enough for this to be a clear win, especially on x86_64;
* system/usbhcd.c: array of same-length strings;
* tests/tests.h: array of structs containing same-length strings.

* Reduce the size of the list of tests by using a narrower type for the cpu mode, which reduces padding.
---
 app/interrupt.c   | 2 +-
 system/jedec_id.h | 4 ++--
 system/usbhcd.c   | 2 +-
 tests/tests.h     | 4 ++--
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/app/interrupt.c b/app/interrupt.c
index 300610c..1a337c0 100644
--- a/app/interrupt.c
+++ b/app/interrupt.c
@@ -56,7 +56,7 @@
 #define ADR_DIGITS  "8"
 #endif
 
-static const char *codes[] = {
+static const char codes[][13] = {
     "Divide by 0",
     "Debug",
     "NMI",
diff --git a/system/jedec_id.h b/system/jedec_id.h
index 83a52f8..39d3082 100644
--- a/system/jedec_id.h
+++ b/system/jedec_id.h
@@ -10,12 +10,12 @@
 #define JEP106_CNT \
     sizeof(jep106)/sizeof(jep106[0])
 
-struct spd_jedec_manufacturer {
+struct __attribute__((packed)) spd_jedec_manufacturer {
     uint16_t jedec_code;
     char *name;
 };
 
-static const struct spd_jedec_manufacturer jep106[] = {
+static const struct __attribute__((packed)) spd_jedec_manufacturer jep106[] = {
     { 0x0001, "AMD" },
 //  { 0x0002, "AMI" },
 //  { 0x0003, "Fairchild" },
diff --git a/system/usbhcd.c b/system/usbhcd.c
index e588504..5824eb1 100644
--- a/system/usbhcd.c
+++ b/system/usbhcd.c
@@ -56,7 +56,7 @@ typedef struct {
 // Private Variables
 //------------------------------------------------------------------------------
 
-static const char *hci_name[MAX_HCI_TYPE] = { "UHCI", "OHCI", "EHCI", "XHCI" };
+static const char hci_name[MAX_HCI_TYPE][5] = { "UHCI", "OHCI", "EHCI", "XHCI" };
 
 static const hcd_methods_t methods = {
     .reset_root_hub_port = NULL,
diff --git a/tests/tests.h b/tests/tests.h
index cc1e1c9..9b5b873 100644
--- a/tests/tests.h
+++ b/tests/tests.h
@@ -18,11 +18,11 @@
 
 typedef struct {
     bool            enabled;
-    cpu_mode_t      cpu_mode;
+    uint8_t         cpu_mode;
     int             stages;
     int             iterations;
     int             errors;
-    char            *description;
+    char            description[40];
 } test_pattern_t;
 
 extern test_pattern_t test_list[NUM_TEST_PATTERNS];