Bug #24571672 DO NOT USE -FNO-EXPENSIVE-OPTIMIZATIONS JUST TO AVOID

FUSED MADD INSTRUCTIONS

The fix for bug #23046775 introduced the -fno-expensive-optimizations
compiler flag on some platforms. This patch lifts that restriction and
instead explicitly turns off fused multiply-add instructions by
setting -ffp-contract=off.

This patch is a contribution from Alexey Kopytov.

Author: nryeng

cmake/build_configurations/compiler_options.cmake

@@ -34,9 +34,9 @@ IF(UNIX)
     IF(WITH_VALGRIND)
       SET(COMMON_C_FLAGS             "-fno-inline ${COMMON_C_FLAGS}")
     ENDIF()
-    # Disable optimizations that change floating point results
-    IF(HAVE_C_FLOATING_POINT_OPTIMIZATION_PROBLEMS)
-      SET(COMMON_C_FLAGS "${COMMON_C_FLAGS} -fno-expensive-optimizations")
+    # Disable floating point expression contractions to avoid result differences
+    IF(HAVE_C_FLOATING_POINT_FUSED_MADD)
+      SET(COMMON_C_FLAGS "${COMMON_C_FLAGS} -ffp-contract=off")
     ENDIF()
     SET(CMAKE_C_FLAGS_DEBUG          "${COMMON_C_FLAGS}")
     SET(CMAKE_C_FLAGS_RELWITHDEBINFO "-O3 ${COMMON_C_FLAGS}")
@@ -53,9 +53,9 @@ IF(UNIX)
     IF(WITH_VALGRIND)
       SET(COMMON_CXX_FLAGS             "-fno-inline ${COMMON_CXX_FLAGS}")
     ENDIF()
-    # Disable optimizations that change floating point results
-    IF(HAVE_CXX_FLOATING_POINT_OPTIMIZATION_PROBLEMS)
-      SET(COMMON_CXX_FLAGS "${COMMON_CXX_FLAGS} -fno-expensive-optimizations")
+    # Disable floating point expression contractions to avoid result differences
+    IF(HAVE_CXX_FLOATING_POINT_FUSED_MADD)
+      SET(COMMON_CXX_FLAGS "${COMMON_CXX_FLAGS} -ffp-contract=off")
     ENDIF()
     SET(CMAKE_CXX_FLAGS_DEBUG          "${COMMON_CXX_FLAGS}")
     SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O3 ${COMMON_CXX_FLAGS}")

cmake/floating_point.cmake

@@ -32,8 +32,8 @@ SET(code "
     /*
       s should now be either 5e 74 d1 45 17 5d 14 40 or
       40 14 5d 17 45 d1 74 5e, depending on endianness. If the floating point
-      operations are over optimized, the least significant byte is 5d instead
-      of 5e.
+      operations are optimized with fused multiply-add instructions, the least
+      significant byte is 5d instead of 5e.
     */
     return (*(unsigned char*)(&s) == 0x5e ||
             *((unsigned char*)(&s) + 7) == 0x5e);
@@ -42,15 +42,15 @@ SET(code "
 
 SET(SAVE_CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")
 SET(CMAKE_REQUIRED_FLAGS
-  "${CMAKE_REQUIRED_FLAGS} -O3 -fexpensive-optimizations"
+  "${CMAKE_REQUIRED_FLAGS} -O3"
 )
 
 IF(CMAKE_COMPILER_IS_GNUCC)
-  CHECK_C_SOURCE_RUNS("${code}" HAVE_C_FLOATING_POINT_OPTIMIZATION_PROBLEMS)
+  CHECK_C_SOURCE_RUNS("${code}" HAVE_C_FLOATING_POINT_FUSED_MADD)
 ENDIF()
 
 IF(CMAKE_COMPILER_IS_GNUCXX)
-  CHECK_CXX_SOURCE_RUNS("${code}" HAVE_CXX_FLOATING_POINT_OPTIMIZATION_PROBLEMS)
+  CHECK_CXX_SOURCE_RUNS("${code}" HAVE_CXX_FLOATING_POINT_FUSED_MADD)
 ENDIF()
 
 SET(CMAKE_REQUIRED_FLAGS "${SAVE_CMAKE_REQUIRED_FLAGS}")

mysql-test/suite/innodb_gis/t/1.test

@@ -371,15 +371,9 @@ insert into t1 values ('85984',ST_GeomFromText('MULTIPOLYGON(((-115.006363
 36.248666,-115.263639 36.247466,-115.263839 36.252766,-115.261439
 36.252666,-115.261439 36.247366,-115.247239 36.247066)))'));
 
-# Expected result is 115.31877315203187, but IA64 returns 115.31877315203188
-# due to fused multiply-add instructions.
---replace_result 115.31877315203188 115.31877315203187
 select object_id, ST_geometrytype(geo), ST_ISSIMPLE(GEO), ST_ASTEXT(ST_centroid(geo)) from
 t1 where object_id=85998;
 
-# Expected result is 36.3310176346905, but IA64 returns 36.3310176346904
-# due to fused multiply-add instructions.
---replace_result 36.3310176346904 36.3310176346905 -114.87787186923326 -114.87787186923313 36.33101763469053 36.33101763469059 36.33101763469043 36.33101763469059
 select object_id, ST_geometrytype(geo), ST_ISSIMPLE(GEO), ST_ASTEXT(ST_centroid(geo)) from
 t1 where object_id=85984;
 

mysql-test/suite/innodb_gis/t/gis.test

@@ -365,15 +365,9 @@ insert into t1 values ('85984',ST_GeomFromText('MULTIPOLYGON(((-115.006363
 36.248666,-115.263639 36.247466,-115.263839 36.252766,-115.261439
 36.252666,-115.261439 36.247366,-115.247239 36.247066)))'));
 
-# Expected result is 115.31877315203187, but IA64 returns 115.31877315203188
-# due to fused multiply-add instructions.
---replace_result 115.31877315203188 115.31877315203187
 select object_id, ST_geometrytype(geo), ST_ISSIMPLE(GEO), ST_ASTEXT(ST_centroid(geo)) from
 t1 where object_id=85998;
 
-# Expected result is 36.3310176346905, but IA64 returns 36.3310176346904
-# due to fused multiply-add instructions.
---replace_result 36.3310176346904 36.3310176346905 -114.87787186923326 -114.87787186923313 36.33101763469053 36.33101763469059 36.33101763469043 36.33101763469059
 select object_id, ST_geometrytype(geo), ST_ISSIMPLE(GEO), ST_ASTEXT(ST_centroid(geo)) from
 t1 where object_id=85984;
 

mysql-test/t/gis.test

@@ -362,15 +362,9 @@ insert into t1 values ('85984',ST_GeomFromText('MULTIPOLYGON(((-115.006363
 36.248666,-115.263639 36.247466,-115.263839 36.252766,-115.261439
 36.252666,-115.261439 36.247366,-115.247239 36.247066)))'));
 
-# Expected result is 115.31877315203187, but IA64 returns 115.31877315203188
-# due to fused multiply-add instructions.
---replace_result 115.31877315203188 115.31877315203187
 select object_id, ST_geometrytype(geo), ST_ISSIMPLE(GEO), ST_ASTEXT(ST_centroid(geo)) from
 t1 where object_id=85998;
 
-# Expected result is 36.3310176346905, but IA64 returns 36.3310176346904
-# due to fused multiply-add instructions.
---replace_result 36.3310176346904 36.3310176346905 -114.87787186923326 -114.87787186923313 36.33101763469053 36.33101763469059 36.33101763469043 36.33101763469059
 select object_id, ST_geometrytype(geo), ST_ISSIMPLE(GEO), ST_ASTEXT(ST_centroid(geo)) from
 t1 where object_id=85984;