[PATCH] D23460: [NVPTX] Use untyped (.b) integer registers in PTX.

[Justin Lebar via llvm-commits]

jlebar added inline comments.

================
Comment at: lib/Target/NVPTX/NVPTXRegisterInfo.cpp:38
@@ +37,3 @@
+    // reduce possibility of triggering ptxas bugs exposed by using
+    // PTX features that are rarely or never never produced by nvcc.
+    return ".b64";
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As written, this comment says we're making this change to avoid the hypothetical possibility of hitting bugs in ptxas in the future.  But that's not really true, right?  My understanding is there's an explicit bug in ptxas with fp16 that we are working around.

We chose to use this big hammer to work around the ptxas bug for the reasons you explain here, and that's also an important part, but it's not the whole story.

Sorry to be nitpicky about this, but spelling it out (ideally with examples of good/bad PTX) is really important so that if someone in the future comes along and wants to change this, they have some chance of being able to evaluate whether they will regress something.


https://reviews.llvm.org/D23460