1.12.2 Gradlew SetupDecompWorkspace memory error

Hey so,

I have been modding on 1.10.2 for a while and decided to update my mods to 1.12.2. I seem to only be able to assign a total of 1Gb to the gradle.properties file, which isn't enough. Upon reaching :decompileMc, it errors for not having 3Gb. If I try allocating anything above 1Gb, I get the same crash but on start up. I have 8Gb on a 64x Win 10 machine. I run Minecraft at 4Gb, I have nothing running on my computer and even turned off some services such as Dropbox and Drive to increase memory availability. I have no idea why the memory cannot be allocated, I would love some help.

Kind regards, Wolf

C:\Users\###\Programming\Minecraft\1.12.2\WolfCore>gradlew setupDecompWorkspace
To honour the JVM settings for this build a new JVM will be forked. Please consider using the daemon: https://docs.gradle.org/2.14/userguide/gradle_daemon.html.
This mapping 'snapshot_20171003' was designed for MC 1.12! Use at your own peril.
#################################################
         ForgeGradle 2.3-SNAPSHOT-4a7d623
  https://github.com/MinecraftForge/ForgeGradle
#################################################
                 Powered by MCP
             http://modcoderpack.com
     by: Searge, ProfMobius, R4wk, ZeuX
     Fesh0r, IngisKahn, bspkrs, LexManos
#################################################
:deobfCompileDummyTask
:deobfProvidedDummyTask
:getVersionJson
:extractUserdev UP-TO-DATE
:extractDependencyATs SKIPPED
:extractMcpData SKIPPED
:extractMcpMappings SKIPPED
:genSrgs SKIPPED
:downloadClient SKIPPED
:downloadServer SKIPPED
:splitServerJar SKIPPED
:mergeJars SKIPPED
:deobfMcSRG SKIPPED
:decompileMc
Error occurred during initialization of VM
Could not reserve enough space for 3145728KB object heap
                                                                                                    :decompileMc FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':decompileMc'.
> Process 'command 'C:\Program Files (x86)\Java\jdk1.8.0_172\bin\java.exe'' finished with non-zero exit value 1

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 31.483 secs

C:\Users\Zac\Programming\Minecraft\1.12.2\WolfCore>