From a04db67ea9d882eed9164321bcb503f76a65d2f1 Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Sun, 4 Aug 2019 15:32:33 +0200
Subject: [PATCH] runtime: work around a bug in LLVM for .bss zeroing

See the following bug: https://bugs.llvm.org/show_bug.cgi?id=42881

I think this is a bug in LLVM, but the code in question wasn't the best
code anyway. By fixing this, about 16 bytes of code are saved on ARM
chips (and much more on AVR).
---
 src/runtime/runtime_avr.go     |  8 ++++----
 src/runtime/runtime_cortexm.go | 20 ++++++++++----------
 src/runtime/runtime_fe310.go   | 20 ++++++++++----------
 3 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/src/runtime/runtime_avr.go b/src/runtime/runtime_avr.go
index 78c6c41c..083b4561 100644
--- a/src/runtime/runtime_avr.go
+++ b/src/runtime/runtime_avr.go
@@ -47,10 +47,10 @@ func main() {
 
 func preinit() {
 	// Initialize .bss: zero-initialized global variables.
-	ptr := uintptr(unsafe.Pointer(&_sbss))
-	for ptr != uintptr(unsafe.Pointer(&_ebss)) {
-		*(*uint8)(unsafe.Pointer(ptr)) = 0
-		ptr += 1
+	ptr := unsafe.Pointer(&_sbss)
+	for ptr != unsafe.Pointer(&_ebss) {
+		*(*uint32)(ptr) = 0
+		ptr = unsafe.Pointer(uintptr(ptr) + 4)
 	}
 }
 
diff --git a/src/runtime/runtime_cortexm.go b/src/runtime/runtime_cortexm.go
index 909206e9..e6b5d294 100644
--- a/src/runtime/runtime_cortexm.go
+++ b/src/runtime/runtime_cortexm.go
@@ -24,19 +24,19 @@ var _edata unsafe.Pointer
 
 func preinit() {
 	// Initialize .bss: zero-initialized global variables.
-	ptr := uintptr(unsafe.Pointer(&_sbss))
-	for ptr != uintptr(unsafe.Pointer(&_ebss)) {
-		*(*uint32)(unsafe.Pointer(ptr)) = 0
-		ptr += 4
+	ptr := unsafe.Pointer(&_sbss)
+	for ptr != unsafe.Pointer(&_ebss) {
+		*(*uint32)(ptr) = 0
+		ptr = unsafe.Pointer(uintptr(ptr) + 4)
 	}
 
 	// Initialize .data: global variables initialized from flash.
-	src := uintptr(unsafe.Pointer(&_sidata))
-	dst := uintptr(unsafe.Pointer(&_sdata))
-	for dst != uintptr(unsafe.Pointer(&_edata)) {
-		*(*uint32)(unsafe.Pointer(dst)) = *(*uint32)(unsafe.Pointer(src))
-		dst += 4
-		src += 4
+	src := unsafe.Pointer(&_sidata)
+	dst := unsafe.Pointer(&_sdata)
+	for dst != unsafe.Pointer(&_edata) {
+		*(*uint32)(dst) = *(*uint32)(src)
+		dst = unsafe.Pointer(uintptr(dst) + 4)
+		src = unsafe.Pointer(uintptr(src) + 4)
 	}
 }
 
diff --git a/src/runtime/runtime_fe310.go b/src/runtime/runtime_fe310.go
index ded5edde..6516877e 100644
--- a/src/runtime/runtime_fe310.go
+++ b/src/runtime/runtime_fe310.go
@@ -62,19 +62,19 @@ func pric_init() {
 
 func preinit() {
 	// Initialize .bss: zero-initialized global variables.
-	ptr := uintptr(unsafe.Pointer(&_sbss))
-	for ptr != uintptr(unsafe.Pointer(&_ebss)) {
-		*(*uint32)(unsafe.Pointer(ptr)) = 0
-		ptr += 4
+	ptr := unsafe.Pointer(&_sbss)
+	for ptr != unsafe.Pointer(&_ebss) {
+		*(*uint32)(ptr) = 0
+		ptr = unsafe.Pointer(uintptr(ptr) + 4)
 	}
 
 	// Initialize .data: global variables initialized from flash.
-	src := uintptr(unsafe.Pointer(&_sidata))
-	dst := uintptr(unsafe.Pointer(&_sdata))
-	for dst != uintptr(unsafe.Pointer(&_edata)) {
-		*(*uint32)(unsafe.Pointer(dst)) = *(*uint32)(unsafe.Pointer(src))
-		dst += 4
-		src += 4
+	src := unsafe.Pointer(&_sidata)
+	dst := unsafe.Pointer(&_sdata)
+	for dst != unsafe.Pointer(&_edata) {
+		*(*uint32)(dst) = *(*uint32)(src)
+		dst = unsafe.Pointer(uintptr(dst) + 4)
+		src = unsafe.Pointer(uintptr(src) + 4)
 	}
 }