[PATCH] D140693: [Driver][RISCV] Adjust the priority between -mcpu, -mtune and -march

[Craig Topper via Phabricator via cfe-commits]

craig.topper added a comment.

This doesn't seem correct

  What's the priority among those options for now(w/o this patch)?
  
  Pipeline model:
  
  Take from -mtune if present.
  Take from -mcpu if present
  Use the default pipeline model: generic-rv32 or generic-rv64
  Architecture extension:
  
  Take from -mcpu if present.
  Take from -march if present.
  Use the default architecture depending on the target triple

The code in `riscv::getRISCVArch` prioritizes -march over -mcpu for architecture extensions for setting -target-features.

But the backend still applies extensions from -target-cpu via the tablegen features from RISCV.td.

So its not even a "priority", we end up with a union.



================
Comment at: clang/lib/Driver/ToolChains/Clang.cpp:5457
+  // RISC-V will handle -mcpu option in Clang::AddRISCVTargetArgs.
+  if (!Triple.isRISCV()) {
+    // Add the target cpu
----------------
I wonder if we should stop getCPUName from calling `getRISCVTargetCPU` instead? Have you audited all callers of getCPUName?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D140693/new/

https://reviews.llvm.org/D140693