Build 32bit Python on Windows with SSE2 instruction set

[animalize]

BPO	36357
Nosy	@pfmoore, @tjguk, @zware, @zooba, @animalize

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2019-03-19.14:03:14.241>
created_at = <Date 2019-03-19.04:36:08.073>
labels = ['build', '3.8', 'OS-windows']
title = 'Build 32bit Python on Windows with SSE2 instruction set'
updated_at = <Date 2019-03-19.14:03:14.240>
user = 'https://github.com/animalize'

bugs.python.org fields:

activity = <Date 2019-03-19.14:03:14.240>
actor = 'malin'
assignee = 'none'
closed = True
closed_date = <Date 2019-03-19.14:03:14.241>
closer = 'malin'
components = ['Build', 'Windows']
creation = <Date 2019-03-19.04:36:08.073>
creator = 'malin'
dependencies = []
files = []
hgrepos = []
issue_num = 36357
keywords = []
message_count = 1.0
messages = ['338317']
nosy_count = 5.0
nosy_names = ['paul.moore', 'tim.golden', 'zach.ware', 'steve.dower', 'malin']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue36357'
versions = ['Python 3.8']

[animalize]

On windows, it seems 32bit builds (3.7.2/3.8.0a2) don't using SSE2 sufficiently.

I test on 3.8 branch, python38.dll only uses XMM register 28 times. The official build is the same.
After enable this option, python38.dll uses XMM register 11,704 times.

--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -88,6 +88,7 @@
       <AdditionalIncludeDirectories Condition="$(IncludeExternals)">$(zlibDir);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <PreprocessorDefinitions>_USRDLL;Py_BUILD_CORE;Py_ENABLE_SHARED;MS_DLL_ID="$(SysWinVer)";%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <PreprocessorDefinitions Condition="$(IncludeExternals)">_Py_HAVE_ZLIB;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <EnableEnhancedInstructionSet Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">StreamingSIMDExtensions2</EnableEnhancedInstructionSet>
     </ClCompile>
     <Link>
       <AdditionalDependencies>version.lib;shlwapi.lib;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>

x86 instruction set has only a few number of registers.
In my understanding, using XMM registers on 32bit build will brings a small speed up.
I'm not an expert of this kind knowledge, sorry if I'm wrong.