From 97c926ea917049885df4ce57cc935062fccf8c50 Mon Sep 17 00:00:00 2001 From: "Earle F. Philhower, III" Date: Mon, 30 Sep 2019 16:27:10 -0700 Subject: [PATCH] Move all PSTRs to own section, allow string dedup (#6565) * Move all PSTRs to own section, allow string dedup GNU ld can deduplicate strings, and does so for most normal char *s automatically. However, for PSTRs we were using a unique section per string *and* the section was not flagges as containing dedupable 0-terminated strings. Modify the PSTR macro to emit assembly, which lets us set the section flags required (SM) for the variables, and use inline assembly to get the asm-block defined address. Should result in smaller compiled binaries if any strings are duplicated. * Give each PSTR its own segment * Allow disposing of unused strings before merging Add the "a" section flag to allow the linker to throw away unneeded strings. Without this flag, the linker will not discard unreferenced strings and ROMs will increase in size, possibly dramatically. --- tools/sdk/ld/eagle.app.v6.common.ld.h | 3 +++ tools/sdk/libc/xtensa-lx106-elf/include/sys/pgmspace.h | 8 +++++++- 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/tools/sdk/ld/eagle.app.v6.common.ld.h b/tools/sdk/ld/eagle.app.v6.common.ld.h index 2f5735fff..383154e49 100644 --- a/tools/sdk/ld/eagle.app.v6.common.ld.h +++ b/tools/sdk/ld/eagle.app.v6.common.ld.h @@ -181,6 +181,9 @@ SECTIONS *libwps.a:(.literal.* .text.*) *(.irom0.literal .irom.literal .irom.text.literal .irom0.text .irom0.text.* .irom.text .irom.text.*) + /* Constant strings in flash (PSTRs) */ + *(.irom0.pstr.*) + /* __FUNCTION__ locals */ *(.rodata._ZZ*__FUNCTION__) *(.rodata._ZZ*__PRETTY_FUNCTION__) diff --git a/tools/sdk/libc/xtensa-lx106-elf/include/sys/pgmspace.h b/tools/sdk/libc/xtensa-lx106-elf/include/sys/pgmspace.h index d74b8b000..20512bed4 100644 --- a/tools/sdk/libc/xtensa-lx106-elf/include/sys/pgmspace.h +++ b/tools/sdk/libc/xtensa-lx106-elf/include/sys/pgmspace.h @@ -23,6 +23,7 @@ extern "C" { // Ref: https://gcc.gnu.org/onlinedocs/gcc-3.2/gcc/Variable-Attributes.html // Place each progmem object into its own named section, avoiding conflicts #define PROGMEM __attribute__((section( "\".irom.text." __FILE__ "." __STRINGIZE(__LINE__) "." __STRINGIZE(__COUNTER__) "\""))) + #define PROGMEM_PSTR "\".irom0.pstr." __FILE__ "." __STRINGIZE(__LINE__) "." __STRINGIZE(__COUNTER__) "\"" #endif #ifndef PGM_P #define PGM_P const char * @@ -34,7 +35,12 @@ extern "C" { // PSTR() macro modified to start on a 32-bit boundary. This adds on average // 1.5 bytes/string, but in return memcpy_P and strcpy_P will work 4~8x faster #ifndef PSTR - #define PSTR(s) (__extension__({static const char __c[] __attribute__((__aligned__(4))) PROGMEM = (s); &__c[0];})) + // Adapted from AVR-specific code at https://forum.arduino.cc/index.php?topic=194603.0 + #define PSTR(str) (__extension__({ \ + PGM_P ptr; \ + asm volatile ( ".pushsection " PROGMEM_PSTR ", \"aSM\", @progbits, 1 \n .align 4 \n 0: .string " __STRINGIZE(str) "\n .popsection \n" ); \ + asm volatile ( "movi %0, 0b" : "=r" (ptr) ); \ + ptr; })) #endif // Flash memory must be read using 32 bit aligned addresses else a processor