Change default -mfpu type to 'vfpv3d16' instead of 'vfp'

'vfp' really corresponds to VFPv2, with 'vfpv3-d16' corresponding
to the mandated minimum FPU architecture for ARMv7-A and hence
armeabi-v7a.

Note that 'vfpv3-d16' adds a few instructions on top of 'vfp' which
relate to loading a small set of immediate values directly into
FPU registers (e.g. +1.0, -1.0, etc). Any code that was previously
generated with -mfpu=vfp will still work, and any code that targets
'vfpv3d16' will work on all armeabi-v7a capable devices.

For more information, see the documentation comments in
sources/android/cpu-features.c introduced in this patch:

  https://android-review.googlesource.com/#/c/44920/

Change-Id: Ice0067a23c8e5dc7cec13cd07f18183164a67730

6 files changed, 10 insertions, 12 deletions

diff --git a/build/tools/build-host-gcc.sh b/build/tools/build-host-gcc.sh
index ea3c73b37..84cb9cc30 100755
--- a/build/tools/build-host-gcc.sh
+++ b/build/tools/build-host-gcc.sh
@@ -1405,7 +1405,7 @@ build_host_gcc_core ()
 
     case $TARGET_ARCH in
         arm)
-            ARGS=$ARGS" --with-arch=armv5te --with-float=soft --with-fpu=vfp"
+            ARGS=$ARGS" --with-arch=armv5te --with-float=soft --with-fpu=vfpv3-d16"
             ;;
         mips)
             # Add --disable-fixed-point to disable fixed-point support
diff --git a/docs/STANDALONE-TOOLCHAIN.html b/docs/STANDALONE-TOOLCHAIN.html
index 51b41025a..59f089da4 100644
--- a/docs/STANDALONE-TOOLCHAIN.html
+++ b/docs/STANDALONE-TOOLCHAIN.html
@@ -165,19 +165,17 @@ It is recommended to use the -mthumb compiler flag to force the generation
 of 16-bit Thumb-1 instructions (the default being 32-bit ARM ones).
 
 If you want to target the 'armeabi-v7a' ABI, you will need ensure that the
-following two flags are being used:
+following flags are being used:
 
-  CFLAGS='-march=armv7-a -mfloat-abi=softfp'
+  CFLAGS='-march=armv7-a -mfloat-abi=softfp -mfpu=vfpv3-d16'
 
 Note: The first flag enables Thumb-2 instructions, and the second one
       enables H/W FPU instructions while ensuring that floating-point
       parameters are passed in core registers, which is critical for
       ABI compatibility. Do *not* use these flags separately!
 
-You may add proper FPU flag, eg. "-mfpu=vfp" (stands for VFPv2, 16 double-precision
-registers), if you target for architecture which supports it.
-
-If you want to use Neon instructions, you will need one more compiler flag:
+If you want to use Neon instructions, you will need to change the -mfpu
+compiler flag:
 
   CFLAGS='-march=armv7-a -mfloat-abi=softfp -mfpu=neon'
 
@@ -188,7 +186,7 @@ Also, make sure the following two flags are provided to linker:
   LDFLAGS='-march=armv7-a -Wl,--fix-cortex-a8'
 
 Note: The first flag instructs linker to pick libgcc.a, libgcov.a and
-      crt*.o tailored for armv7.  The 2nd flag is *required* to routes
+      crt*.o tailored for armv7-a.  The 2nd flag is *required* to route
       around a CPU bug in some Cortex-A8 implementations:
 
 If none of the above makes sense to you, it's probably better not to use
diff --git a/toolchains/arm-linux-androideabi-4.4.3/setup.mk b/toolchains/arm-linux-androideabi-4.4.3/setup.mk
index bd58c0483..80302e784 100644
--- a/toolchains/arm-linux-androideabi-4.4.3/setup.mk
+++ b/toolchains/arm-linux-androideabi-4.4.3/setup.mk
@@ -39,7 +39,7 @@ TARGET_C_INCLUDES := \
 ifeq ($(TARGET_ARCH_ABI),armeabi-v7a)
     TARGET_CFLAGS += -march=armv7-a \
                      -mfloat-abi=softfp \
-                     -mfpu=vfp
+                     -mfpu=vfpv3-d16
 
     TARGET_LDFLAGS += -march=armv7-a \
                      -Wl,--fix-cortex-a8
diff --git a/toolchains/arm-linux-androideabi-4.6/setup.mk b/toolchains/arm-linux-androideabi-4.6/setup.mk
index 1fad30f87..6c9d516c5 100644
--- a/toolchains/arm-linux-androideabi-4.6/setup.mk
+++ b/toolchains/arm-linux-androideabi-4.6/setup.mk
@@ -39,7 +39,7 @@ TARGET_C_INCLUDES := \
 ifeq ($(TARGET_ARCH_ABI),armeabi-v7a)
     TARGET_CFLAGS += -march=armv7-a \
                      -mfloat-abi=softfp \
-                     -mfpu=vfp
+                     -mfpu=vfpv3-d16
 
     TARGET_LDFLAGS += -march=armv7-a \
                      -Wl,--fix-cortex-a8
diff --git a/toolchains/arm-linux-androideabi-4.7/setup.mk b/toolchains/arm-linux-androideabi-4.7/setup.mk
index 19cc1459c..bd756afb9 100644
--- a/toolchains/arm-linux-androideabi-4.7/setup.mk
+++ b/toolchains/arm-linux-androideabi-4.7/setup.mk
@@ -39,7 +39,7 @@ TARGET_C_INCLUDES := \
 ifeq ($(TARGET_ARCH_ABI),armeabi-v7a)
     TARGET_CFLAGS += -march=armv7-a \
                      -mfloat-abi=softfp \
-                     -mfpu=vfp
+                     -mfpu=vfpv3-d16
 
     TARGET_LDFLAGS += -march=armv7-a \
                      -Wl,--fix-cortex-a8
diff --git a/toolchains/arm-linux-androideabi-clang3.1/setup.mk b/toolchains/arm-linux-androideabi-clang3.1/setup.mk
index dcb9c2c0e..558ffd311 100644
--- a/toolchains/arm-linux-androideabi-clang3.1/setup.mk
+++ b/toolchains/arm-linux-androideabi-clang3.1/setup.mk
@@ -68,7 +68,7 @@ ifeq ($(TARGET_ARCH_ABI),armeabi-v7a)
     TARGET_CFLAGS += -target $(LLVM_TRIPLE) \
                      -march=armv7-a \
                      -mfloat-abi=softfp \
-                     -mfpu=vfp
+                     -mfpu=vfpv3-d16
 
     TARGET_LDFLAGS += -target $(LLVM_TRIPLE) \
                       -Wl,--fix-cortex-a8