[PATCH] D26725: AMDGPU: Add llvm.amdgcn.interp.mov intrinsic

[Matt Arsenault via llvm-commits]

arsenm added inline comments.


================
Comment at: include/llvm/IR/IntrinsicsAMDGPU.td:481
+            [llvm_i32_ty, llvm_i32_ty, llvm_i32_ty, llvm_i32_ty],
+            [IntrNoMem]>;
+
----------------
mareko wrote:
> nhaehnle wrote:
> > arsenm wrote:
> > > nhaehnle wrote:
> > > > tstellarAMD wrote:
> > > > > arsenm wrote:
> > > > > > Shouldn't this be IntrReadMem? The doc says it reads parameters in LDS
> > > > > I think technically, this should be inaccessiblememonly,  because but there is no intrinsic attribute for this yet.
> > > > And that region of LDS is constant anyway, so IntrNoMem is fine.
> > > Is that possible? I thought the runtime couldn't ever initialize LDS, so something in the shader has to set it in the first place
> > The LDS for these instructions is initialized by Primitive Assembly (or possibly the Scan Converter, it's unclear to me where the boundary between those hardware blocks is precisely).
> LDS is initialized by the SPI block before the pixel shader. ReadNone is fine, because nothing can modify it.
I don't think it can really prevent writes? I'm betting an out of bounds access will clobber it. BTW D26485 adds the property 


https://reviews.llvm.org/D26725