Use volatile in readfe/readff/writeef/writeff/writexf.

The xlc compiler will optimize out the while loop in these functions even with -O0. Use the volatile keyword to protect these accesses to shared memory instead.
stingergraph · Nov 21, 2016 · 0eb1f54 · 0eb1f54
1 parent 19fbb3b
commit 0eb1f54
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Showing 3 changed files with 12 additions and 15 deletions.
diff --git a/lib/stinger_core/CMakeLists.txt b/lib/stinger_core/CMakeLists.txt
@@ -8,6 +8,7 @@ set(sources
 	src/stinger_shared.c
 	src/stinger_vertex.c
 	src/xmalloc.c
+	src/x86_full_empty.c
 )
 set(headers
 	inc/core_util.h
@@ -24,9 +25,6 @@ set(headers
 	inc/x86_full_empty.h
 	inc/xmalloc.h
 )
-set(unoptimized_sources
-	src/x86_full_empty.c
-)
 
 set(config
 	stinger_names.h
@@ -39,6 +37,5 @@ include_directories("${CMAKE_BINARY_DIR}/include/stinger_core")
 include_directories("${CMAKE_BINARY_DIR}/include/stinger_utils")
 
 set_source_files_properties(${config} PROPERTIES GENERATED TRUE)
-set_source_files_properties(${unoptimized_sources} PROPERTIES COMPILE_FLAGS -O0)
-add_library(stinger_core SHARED ${sources} ${unoptimized_sources} ${headers} ${config})
+add_library(stinger_core SHARED ${sources} ${headers} ${config})
 target_link_libraries(stinger_core compat)
diff --git a/lib/stinger_core/inc/x86_full_empty.h b/lib/stinger_core/inc/x86_full_empty.h
@@ -27,19 +27,19 @@ extern "C" {
 #define MARKER UINT64_MAX
 
 uint64_t 
-readfe(uint64_t * v);
+readfe(volatile uint64_t * v);
 
 uint64_t
-writeef(uint64_t * v, uint64_t new_val);
+writeef(volatile uint64_t * v, uint64_t new_val);
 
 uint64_t
-readff(uint64_t * v);
+readff(volatile uint64_t * v);
 
 uint64_t
-writeff(uint64_t * v, uint64_t new_val);
+writeff(volatile uint64_t * v, uint64_t new_val);
 
 uint64_t
-writexf(uint64_t * v, uint64_t new_val);
+writexf(volatile uint64_t * v, uint64_t new_val);
 
 #ifdef __cplusplus
 }

diff --git a/lib/stinger_core/src/x86_full_empty.c b/lib/stinger_core/src/x86_full_empty.c
@@ -16,7 +16,7 @@
 #include  "x86_full_empty.h"
 
 uint64_t 
-readfe(uint64_t * v) {
+readfe(volatile uint64_t * v) {
   uint64_t val;
   while(1) {
     val = *v;
@@ -30,7 +30,7 @@ readfe(uint64_t * v) {
 }
 
 uint64_t
-writeef(uint64_t * v, uint64_t new_val) {
+writeef(volatile uint64_t * v, uint64_t new_val) {
   uint64_t val;
   while(1) {
     val = *v;
@@ -44,7 +44,7 @@ writeef(uint64_t * v, uint64_t new_val) {
 }
 
 uint64_t
-readff(uint64_t * v) {
+readff(volatile uint64_t * v) {
   uint64_t val = *v;
   while(val == MARKER) {
     val = *v;
@@ -53,7 +53,7 @@ readff(uint64_t * v) {
 }
 
 uint64_t
-writeff(uint64_t * v, uint64_t new_val) {
+writeff(volatile uint64_t * v, uint64_t new_val) {
   uint64_t val;
   while(1) {
     val = *v;
@@ -67,7 +67,7 @@ writeff(uint64_t * v, uint64_t new_val) {
 }
 
 uint64_t
-writexf(uint64_t * v, uint64_t new_val) {
+writexf(volatile uint64_t * v, uint64_t new_val) {
   *v = new_val;
   return new_val;
 }