[llvm] [AMDGPU] Add flag to control VGPR pressure limits (PR #203797)

[Lucas Ramirez via llvm-commits]

================
@@ -103,6 +103,34 @@ static cl::opt<bool> DisableRewriteMFMAFormSchedStage(
     "amdgpu-disable-rewrite-mfma-form-sched-stage", cl::Hidden,
     cl::desc("Disable rewrite mfma rewrite scheduling stage"), cl::init(true));
 
+namespace {
+
+struct VGPRThresholdParser : public cl::parser<unsigned> {
+  VGPRThresholdParser(cl::Option &O) : cl::parser<unsigned>(O) {}
+
+  bool parse(cl::Option &O, StringRef ArgName, StringRef Arg, unsigned &Value) {
+    if (Arg.getAsInteger(0, Value))
+      return O.error("'" + Arg + "' value invalid for uint argument!");
+
+    if (Value > 100)
+      return O.error("'" + Arg + "' value must be in the range [0, 100]!");
+
+    return false;
+  }
+};
+
+} // end anonymous namespace
+
+static cl::opt<unsigned, false, VGPRThresholdParser>
+    VGPRExcessThresholdPercentOpt(
+        "amdgpu-vgpr-excess-threshold-percent", cl::Hidden,
+        cl::desc(
+            "Percent of maximum available VGPRs to use as excess RP threshold "
+            "during  scheduling (0 = use default calculation, 1-100 = use "
----------------
lucas-rami wrote:

```suggestion
            "during scheduling (0 = use default calculation, 1-100 = use "
```

https://github.com/llvm/llvm-project/pull/203797