all: prototype of RAM persistence across reset

Makefile

@@ -236,6 +236,8 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/test
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/persistence
+	@$(MD5SUM) test.hex
 	# test simulated boards on play.tinygo.org
 	$(TINYGO) build             -o test.wasm -tags=arduino              examples/blinky1
 	@$(MD5SUM) test.wasm

compiler/compiler.go

@@ -709,11 +709,11 @@ func (c *compilerContext) createPackage(irbuilder llvm.Builder, pkg *ssa.Package
 		member := pkg.Members[name]
 		switch member := member.(type) {
 		case *ssa.Function:
+			// Create the function definition.
+			b := newBuilder(c, irbuilder, member)
 			if member.Blocks == nil {
 				continue // external function
 			}
-			// Create the function definition.
-			b := newBuilder(c, irbuilder, member)
 			b.createFunction()
 		case *ssa.Type:
 			if types.IsInterface(member.Type()) {
@@ -752,10 +752,13 @@ func (c *compilerContext) createPackage(irbuilder llvm.Builder, pkg *ssa.Package
 		case *ssa.Global:
 			// Global variable.
 			info := c.getGlobalInfo(member)
+			global := c.getGlobal(member)
 			if !info.extern {
-				global := c.getGlobal(member)
 				global.SetInitializer(llvm.ConstNull(global.Type().ElementType()))
 				global.SetVisibility(llvm.HiddenVisibility)
+				if info.section != "" {
+					global.SetSection(info.section)
+				}
 			}
 		}
 	}
@@ -781,6 +784,9 @@ func (b *builder) createFunction() {
 		b.llvmFn.SetVisibility(llvm.HiddenVisibility)
 		b.llvmFn.SetUnnamedAddr(true)
 	}
+	if b.info.section != "" {
+		b.llvmFn.SetSection(b.info.section)
+	}
 	if b.info.exported && strings.HasPrefix(b.Triple, "wasm") {
 		// Set the exported name. This is necessary for WebAssembly because
 		// otherwise the function is not exported.

compiler/compiler_test.go

@@ -62,6 +62,7 @@ func TestCompiler(t *testing.T) {
 		"string.go",
 		"float.go",
 		"interface.go",
+		"pragma.go",
 	}
 
 	for _, testCase := range tests {

compiler/symbol.go

@@ -24,6 +24,7 @@ type functionInfo struct {
 	module     string     // go:wasm-module
 	importName string     // go:linkname, go:export - The name the developer assigns
 	linkName   string     // go:linkname, go:export - The name that we map for the particular module -> importName
+	section    string     // go:section - object file section name
 	exported   bool       // go:export, CGo
 	nobounds   bool       // go:nobounds
 	variadic   bool       // go:variadic (CGo only)
@@ -259,6 +260,10 @@ func (info *functionInfo) parsePragmas(f *ssa.Function) {
 				if hasUnsafeImport(f.Pkg.Pkg) {
 					info.linkName = parts[2]
 				}
+			case "//go:section":
+				if len(parts) == 2 {
+					info.section = parts[1]
+				}
 			case "//go:nobounds":
 				// Skip bounds checking in this function. Useful for some
 				// runtime functions.
@@ -314,6 +319,7 @@ type globalInfo struct {
 	linkName string // go:extern
 	extern   bool   // go:extern
 	align    int    // go:align
+	section  string // go:section
 }
 
 // loadASTComments loads comments on globals from the AST, for use later in the
@@ -425,6 +431,10 @@ func (info *globalInfo) parsePragmas(doc *ast.CommentGroup) {
 			if err == nil {
 				info.align = align
 			}
+		case "//go:section":
+			if len(parts) == 2 {
+				info.section = parts[1]
+			}
 		}
 	}
 }

compiler/testdata/pragma.go

@@ -0,0 +1,66 @@
+package main
+
+import _ "unsafe"
+
+// Creates an external global with name extern_global.
+//go:extern extern_global
+var externGlobal [0]byte
+
+// Creates a
+//go:align 32
+var alignedGlobal [4]uint32
+
+// Test conflicting pragmas (the last one counts).
+//go:align 64
+//go:align 16
+var alignedGlobal16 [4]uint32
+
+// Test exported functions.
+//export extern_func
+func externFunc() {
+}
+
+// Define a function in a different package using go:linkname.
+//go:linkname withLinkageName1 somepkg.someFunction1
+func withLinkageName1() {
+}
+
+// Import a function from a different package using go:linkname.
+//go:linkname withLinkageName2 somepkg.someFunction2
+func withLinkageName2()
+
+// Function has an 'inline hint', similar to the inline keyword in C.
+//go:inline
+func inlineFunc() {
+}
+
+// Function should never be inlined, equivalent to GCC
+// __attribute__((noinline)).
+//go:noinline
+func noinlineFunc() {
+}
+
+// This function should have the specified section.
+//go:section .special_function_section
+func functionInSection() {
+}
+
+//export exportedFunctionInSection
+//go:section .special_function_section
+func exportedFunctionInSection() {
+}
+
+// This function should not: it's only a declaration and not a definition.
+//go:section .special_function_section
+func undefinedFunctionNotInSection()
+
+//go:section .special_global_section
+var globalInSection uint32
+
+//go:section .special_global_section
+//go:extern undefinedGlobalNotInSection
+var undefinedGlobalNotInSection uint32
+
+//go:align 1024
+//go:section .global_section
+var multipleGlobalPragmas uint32

compiler/testdata/pragma.ll

@@ -0,0 +1,57 @@
+; ModuleID = 'pragma.go'
+source_filename = "pragma.go"
+target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i686--linux"
+
+@extern_global = external global [0 x i8]
+@main.alignedGlobal = hidden global [4 x i32] zeroinitializer, align 32
+@main.alignedGlobal16 = hidden global [4 x i32] zeroinitializer, align 16
+@main.globalInSection = hidden global i32 0, section ".special_global_section"
+@undefinedGlobalNotInSection = external global i32
+@main.multipleGlobalPragmas = hidden global i32 0, section ".global_section", align 1024
+
+declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)
+
+define hidden void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  ret void
+}
+
+define void @extern_func() {
+entry:
+  ret void
+}
+
+define hidden void @somepkg.someFunction1(i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  ret void
+}
+
+declare void @somepkg.someFunction2(i8*, i8*)
+
+; Function Attrs: inlinehint
+define hidden void @main.inlineFunc(i8* %context, i8* %parentHandle) unnamed_addr #0 {
+entry:
+  ret void
+}
+
+; Function Attrs: noinline
+define hidden void @main.noinlineFunc(i8* %context, i8* %parentHandle) unnamed_addr #1 {
+entry:
+  ret void
+}
+
+define hidden void @main.functionInSection(i8* %context, i8* %parentHandle) unnamed_addr section ".special_function_section" {
+entry:
+  ret void
+}
+
+define void @exportedFunctionInSection() section ".special_function_section" {
+entry:
+  ret void
+}
+
+declare void @main.undefinedFunctionNotInSection(i8*, i8*)
+
+attributes #0 = { inlinehint }
+attributes #1 = { noinline }

src/examples/persistence/main.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"time"
+)
+
+//go:section .persist
+var buffer [32]byte
+
+func main() {
+	println("\n*** ** * RESET * ** ***\n")
+
+	for {
+		time.Sleep(1 * time.Second)
+
+		println("value: ", buffer[0])
+		buffer[0]++
+	}
+}

targets/arm.ld

@@ -31,6 +31,17 @@ SECTIONS
         _stack_top = .;
     } >RAM
 
+    /* Persistent RAM that is not re-initialized on reset.  PRAM is either
+     * a specific area of RAM which is powered during low-power states, or
+     * will be an alias for main system RAM on devices without such support. */
+    .persist (NOLOAD) :
+    {
+        . = ALIGN(4);
+        *(.persist)
+        *(.persist.*)
+        . = ALIGN(4);
+    } >PRAM
+
     /* Start address (in flash) of .data, used by startup code. */
     _sidata = LOADADDR(.data);
 

targets/atsamd21.ld

@@ -5,6 +5,9 @@ MEMORY
     RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x00008000
 }
 
+# Allocate 'Persistent RAM' from regular RAM (some chips have specific PRAM)
+REGION_ALIAS("PRAM", RAM);
+
 _stack_size = 2K;
 
 INCLUDE "targets/arm.ld"

targets/atsamd51.ld

@@ -5,6 +5,9 @@ MEMORY
     RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x00030000
 }
 
+# Allocate 'Persistent RAM' from regular RAM (some chips have specific PRAM)
+REGION_ALIAS("PRAM", RAM);
+
 _stack_size = 4K;
 
 INCLUDE "targets/arm.ld"

targets/atsamd51j20a.ld

@@ -5,6 +5,9 @@ MEMORY
     RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x00040000
 }
 
+# Allocate 'Persistent RAM' from regular RAM (some chips have specific PRAM)
+REGION_ALIAS("PRAM", RAM);
+
 _stack_size = 4K;
 
 INCLUDE "targets/arm.ld"

targets/avr.ld

@@ -23,6 +23,17 @@ SECTIONS
         _stack_top = .;
     } >RAM
 
+    /* Persistent RAM that is not re-initialized on reset.  PRAM is either
+     * a specific area of RAM which is powered during low-power states, or
+     * will be an alias for main system RAM on devices without such support. */
+    .persist (NOLOAD) :
+    {
+        . = ALIGN(4);
+        *(.persist)
+        *(.persist.*)
+        . = ALIGN(4);
+    } >PRAM
+
     _sidata = LOADADDR(.data);
 
     .data :

targets/circuitplay-bluefruit.ld

@@ -5,6 +5,9 @@ MEMORY
     RAM (xrw)       : ORIGIN = 0x20004180, LENGTH = 37K
 }
 
+# Allocate 'Persistent RAM' from regular RAM (some chips have specific PRAM)
+REGION_ALIAS("PRAM", RAM);
+
 _stack_size = 2K;
 
 /* This value is needed by the Nordic SoftDevice. */

targets/esp32.ld

@@ -14,6 +14,9 @@ MEMORY
 
     /* Instruction RAM. */
     IRAM  (x)  : ORIGIN = 0x40080000, LENGTH = 128K /* Internal SRAM 0 */
+
+    /* Persistent RAM.  Data storage across low-power states */
+    PRAM  (rw) : ORIGIN = 0x3FF80000, LENGTH = 8K /* RTC FAST Memory */
 }
 
 /* The entry point. It is set in the image flashed to the chip, so must be
@@ -45,6 +48,15 @@ SECTIONS
         _stack_top = .;
     } >DRAM
 
+    /* Persistent RAM that is not re-initialized on wake-from-sleep. */
+    .persist (NOLOAD) :
+    {
+        . = ALIGN(4);
+        *(.persist)
+        *(.persist.*)
+        . = ALIGN(4);
+    } >PRAM
+
     /* Constant global variables.
      * They are loaded in DRAM for ease of use. Eventually they should be stored
      * in flash and loaded directly from there but they're kept in RAM to make

targets/esp8266.ld

@@ -46,6 +46,15 @@ SECTIONS
         _ebss = ABSOLUTE(.);
     } >DRAM
 
+    /* Persistent RAM emulated using normal RAM. */
+    .persist (NOLOAD) :
+    {
+        . = ALIGN(4);
+        *(.persist)
+        *(.persist.*)
+        . = ALIGN(4);
+    } >DRAM
+
     /* Constant literals and code. Loaded into IRAM for now. Eventually, most
      * code should be executed directly from flash.
      * Note that literals must be before code for the l32r instruction to work.

targets/hifive1-qemu.ld

@@ -8,6 +8,9 @@ MEMORY
     RAM (xrw)       : ORIGIN = 0x80000000, LENGTH = 0x4000
 }
 
+# Allocate 'Persistent RAM' from regular RAM (some chips have specific PRAM)
+REGION_ALIAS("PRAM", RAM);
+
 _stack_size = 2K;
 
 INCLUDE "targets/riscv.ld"

targets/hifive1b.ld

@@ -5,6 +5,9 @@ MEMORY
     RAM (xrw)       : ORIGIN = 0x80000000, LENGTH = 0x4000
 }
 
+# Allocate 'Persistent RAM' from regular RAM (some chips have specific PRAM)
+REGION_ALIAS("PRAM", RAM);
+
 _stack_size = 2K;
 
 INCLUDE "targets/riscv.ld"

targets/lm3s6965.ld

@@ -5,6 +5,9 @@ MEMORY
     RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 64K
 }
 
+# Allocate 'Persistent RAM' from regular RAM (some chips have specific PRAM)
+REGION_ALIAS("PRAM", RAM);
+
 _stack_size = 4K;
 
 INCLUDE "targets/arm.ld"