[llvm] [RISCV] add load/store misched/PostRA cluster options (PR #149409)

[Daniel Henrique Barboza via llvm-commits]

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@@ -94,14 +94,24 @@ static cl::opt<bool>
                            cl::desc("Enable the loop data prefetch pass"),
                            cl::init(true));
 
-static cl::opt<bool> EnableMISchedLoadStoreClustering(
-    "riscv-misched-load-store-clustering", cl::Hidden,
-    cl::desc("Enable load and store clustering in the machine scheduler"),
+static cl::opt<bool> EnableMISchedLoadClustering(
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danielhb wrote:

Changing the default settings of load/store clustering breaks 290+ tests in check-llvm. This shows that there's a LOT of code and logic built on top of the existing default. I don't want to touch this viper nest in this work so I'll keep the default as is. This means that  the subtarget features will disable the default settings instead of enabling - TuneNoDefaultUnroll would be an example.

Also, after adding both the command line options and subtarget features I realized that I might be complicating things too much, given that we can override the subtarget features via "mattr=-<feature>" anyway, so I'll change the code to send just the subtarget features.  I'll send a new version shortly.

https://github.com/llvm/llvm-project/pull/149409