Qt apps can't exploit the hardware FPU on Symbian^3 devices

SDK 1.1 doesn't provide a way for ISVs to build apps which use the FPU on Symbian^3 devices.

The diff posted below causes all Symbian^3 apps to build using ARM ISA and VFPv2 instructions (instead of the default Thumb ISA and AEABI helper calls for floating-point operations). With this diff, my floating-point code runs 5x-8x faster than without it.

Because this causes code to build using ARM, not Thumb, there is a slight binary-size bloat for non-floating-point programs (perhaps 50%) which also reduces performance (perhaps by 5%). Therefore this hack is not recommended as the requested fix – rather, there needs to be a project-specific option (eg in the .pro file) to enable ISVs to make this choice.

This is only requested for Symbian^3 and later. In Symbian^1 and earlier, there are a (very) few models with a kernel bug which means that enabling floating-point isn't actually safe.

Finally note that this is not the same as QTBUG-14244 which requests that the Qt runtime itself (or more significant parts of it) be built with hardware floating-point enabled. That is a quite separate question, from enabling ISVs to choose whether to build ther apps with floating-point.

Here's the diff:

diff --git a/tools/sbs/lib/config/gcce.xml b/tools/sbs/lib/config/gcce.xml
index d11e449..91b7510 100644
— a/tools/sbs/lib/config/gcce.xml
+++ b/tools/sbs/lib/config/gcce.xml
@@ -25,7 +25,7 @@
<set name="ASSEMBLER_LISTING_OPTION" value="-S"/>
<set name="BPABI_OPTION" value=""/>
<set name="C_LANG_OPTION" value="-x c"/>

• <set name="CC.ARMV5" value="-march=armv5t"/>
  + <set name="CC.ARMV5" value="-march=armv6"/>
  <set name="CC.ARMV6" value="-march=armv6t2"/>
  <set name="CC.ARMV7" value="-march=armv7"/>
  <!-- From the GCC manual: "With this option, GCC uses features of DWARF version 3 when they are useful; ..." -->
  @@ -33,7 +33,7 @@
  <set name="CC.DWARF2" value="-gdwarf-2"/>
  <set name="CC.DWARF3" value="-gdwarf-2"/>
  <set name="CC.NO_UNALIGNED_ACCESS" value=""/>
• <set name="CC.SOFTVFP_MAYBE_VFPV2" value="soft"/>
  + <set name="CC.SOFTVFP_MAYBE_VFPV2" value="softfp"/>
  <set name="CC.SOFTVFP_MAYBE_VFPV3" value="soft"/>
  <set name="CC_ERRORS_CONTROL_OPTION" value=""/>
  <set name="CC_WARNINGS_CONTROL_OPTION" value="-Wall -Wno-unknown-pragmas"/>
  @@ -42,7 +42,7 @@
  <set name="COMMANDFILE_OPTION" value="@"/>
  <set name="COMPILE_ONLY_OPTION" value="-c"/>
  <set name="COMPILER_CIA_FLAGS" value="-marm"/>
• <set name="COMPILER_FPU_OPTION" value="-mfloat-abi="/>
  + <set name="COMPILER_FPU_OPTION" value="-mfpu=vfp -mfloat-abi="/>
  <set name="COMPILER_INTERWORK_DEFINES" value="_MARM_INTERWORK_"/>
  <set name="COMPILER_NO_HIDE_ALL_OPTION" value="-fvisibility=default"/>
  <set name="COMPILER_SYSTEM_INCLUDE_OPTION" value="-I"/>
  diff --git a/tools/sbs/lib/flm/standard.xml b/tools/sbs/lib/flm/standard.xml
  index f0deac5..224272a 100644
  • • a/tools/sbs/lib/flm/standard.xml
      +++ b/tools/sbs/lib/flm/standard.xml
      @@ -2,10 +2,10 @@
      <build xmlns="http://symbian.com/xml/build" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://symbian.com/xml/build ../../schema/build/2_0.xsd">
      <interface name="Symbian.mmp" extends="base.flm" abstract="true">
      <param name='AAPCS_OPTION'/>
• <param name='ALWAYS_BUILD_AS_ARM' default=''/>
  + <param name='ALWAYS_BUILD_AS_ARM' default='yes'/>
  <param name='SET_ARMINC' default=''/>
  <param name='ARMLIBS' default=''/>
• <param name='ARMFPU' default=''/>
  + <param name='ARMFPU' default=''/>
  <param name='ARMRT' default=''/>
  <param name='BYTEPAIRCOMPRESSTARGET' default=''/>
  <param name='TESTPATH' default=''/>