[GitHub] [tvm] joshherr-quic commented on a diff in pull request #12639: [HEXAGON] Disable automatic unrolling in LLVM

[GitBox <gi...@apache.org>]

joshherr-quic commented on code in PR #12639:
URL: https://github.com/apache/tvm/pull/12639#discussion_r974500764


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src/target/llvm/codegen_hexagon.cc:
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@@ -513,6 +513,13 @@ runtime::Module BuildHexagon(IRModule mod, Target target) {
                           {"-hexagon-small-data-threshold=0",
                            "-force-target-max-vector-interleave=1", "-hexagon-autohvx=1"});
 
+  // Disable unrolling (bug fix in LLVM 16 for int8 vectors)
+  // TODO: figure out why unroll is causing significant compile
+  // time and binary size issues for bert int8 model among others.
+#if TVM_LLVM_VERSION >= 160
+  llvm_options_vec.insert({"-unroll-threshold=0"})
+#endif

Review Comment:
   That's a good point, but I don't expect this workaround to be in here for a particularly long time. There aren't any active plans to put the related LLVM patch in any releases <= 16.0, so it would surprise me if someone ran into this without knowing about the issue specifically, in which case they could make the needed adjustments to gate their llvm in.
   
   I think if this were a permanent solution, some cmake magic would be nice, but since it is just a workaround, nobody should (hopefully) run into it before a real fix is issued.



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