Micro-optimization as discussed here:
https://swiftshader-review.googlesource.com/c/SwiftShader/+/34528/7/src/Pipeline/SpirvShader.hpp#1257

Change-Id: I0e71f2b5c882b2e65271a2e8f114239a924462f8
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/34549Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>