[SandboxVec] Add BottomUpVec test flag to build regions from metadata.

This allows us to write lit tests for region passes where regions are
specified by metadata in textual IR. See added test file for an example.

Author: slackito

llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/Passes/PrintInstructionCountPass.h

@@ -0,0 +1,24 @@
+#ifndef LLVM_TRANSFORMS_VECTORIZE_SANDBOXVECTORIZER_PASSES_PRINTINSTRUCTIONCOUNTPASS_H
+#define LLVM_TRANSFORMS_VECTORIZE_SANDBOXVECTORIZER_PASSES_PRINTINSTRUCTIONCOUNTPASS_H
+
+#include "llvm/SandboxIR/Pass.h"
+
+namespace llvm::sandboxir {
+
+class Region;
+
+/// A Region pass that prints the instruction count for the region to stdout.
+/// Used to test -sbvec-passes while we don't have any actual optimization
+/// passes.
+class PrintInstructionCountPass final : public RegionPass {
+public:
+  PrintInstructionCountPass() : RegionPass("null") {}
+  bool runOnRegion(Region &R) final {
+    outs() << "InstructionCount: " << std::distance(R.begin(), R.end()) << "\n";
+    return false;
+  }
+};
+
+} // namespace llvm::sandboxir
+
+#endif // LLVM_TRANSFORMS_VECTORIZE_SANDBOXVECTORIZER_PASSES_PRINTINSTRUCTIONCOUNTPASS_H

llvm/lib/Transforms/Vectorize/SandboxVectorizer/Passes/BottomUpVec.cpp

@@ -10,15 +10,22 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/SandboxIR/Function.h"
 #include "llvm/SandboxIR/Instruction.h"
+#include "llvm/SandboxIR/Region.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Transforms/Vectorize/SandboxVectorizer/Passes/NullPass.h"
+#include "llvm/Transforms/Vectorize/SandboxVectorizer/Passes/PrintInstructionCountPass.h"
 
 namespace llvm::sandboxir {
 
 static cl::opt<bool>
     PrintPassPipeline("sbvec-print-pass-pipeline", cl::init(false), cl::Hidden,
                       cl::desc("Prints the pass pipeline and returns."));
 
+static cl::opt<bool> UseRegionsFromMetadata(
+    "sbvec-use-regions-from-metadata", cl::init(false), cl::Hidden,
+    cl::desc("Skips bottom-up vectorization, builds regions from metadata "
+             "already present in the IR and runs the region pass pipeline."));
+
 /// A magic string for the default pass pipeline.
 static const char *DefaultPipelineMagicStr = "*";
 
@@ -86,6 +93,14 @@ bool BottomUpVec::runOnFunction(Function &F) {
     RPM.printPipeline(outs());
     return false;
   }
+  if (UseRegionsFromMetadata) {
+    SmallVector<std::unique_ptr<Region>> Regions =
+        Region::createRegionsFromMD(F);
+    for (auto &R : Regions) {
+      RPM.runOnRegion(*R);
+    }
+    return false;
+  }
 
   Change = false;
   // TODO: Start from innermost BBs first

llvm/lib/Transforms/Vectorize/SandboxVectorizer/Passes/PassRegistry.def

@@ -18,5 +18,6 @@
 #endif
 
 REGION_PASS("null", NullPass())
+REGION_PASS("print-instruction-count", PrintInstructionCountPass())
 
 #undef REGION_PASS

llvm/test/Transforms/SandboxVectorizer/regions-from-metadata.ll

@@ -0,0 +1,16 @@
+; RUN: opt -disable-output --passes=sandbox-vectorizer \
+; RUN:    -sbvec-passes=print-instruction-count \
+; RUN:    -sbvec-use-regions-from-metadata %s | FileCheck %s
+
+define i8 @foo(i8 %v0, i8 %v1) {
+  %t0 = add i8 %v0, 1, !sandboxvec !0
+  %t1 = add i8 %t0, %v1, !sandboxvec !1
+  %t2 = add i8 %t1, %v1, !sandboxvec !1
+  ret i8 %t2
+}
+
+!0 = distinct !{!"sandboxregion"}
+!1 = distinct !{!"sandboxregion"}
+
+; CHECK: InstructionCount: 1
+; CHECK: InstructionCount: 2