[PATCH] D19286: Refine instruction weight annotation algorithm for sample profiler.

[Dehao Chen via llvm-commits]

danielcdh created this revision.
danielcdh added reviewers: dnovillo, davidxl.
danielcdh added a subscriber: llvm-commits.

This patch refined the instruction weight anootation algorithm:
1. Do not use dbg_value intrinsics for annotation.
2. Annotate cold calls if the call is inlined in profile, but not inlined before preparation. This indicates that the annotation preparation step found no sample for the inlined callsite, thus the call should be very cold.

http://reviews.llvm.org/D19286

Files:
  lib/Transforms/IPO/SampleProfile.cpp

Index: lib/Transforms/IPO/SampleProfile.cpp
===================================================================
--- lib/Transforms/IPO/SampleProfile.cpp
+++ lib/Transforms/IPO/SampleProfile.cpp
@@ -34,6 +34,7 @@
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/InstIterator.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/MDBuilder.h"
@@ -452,6 +453,12 @@
   if (!FS)
     return std::error_code();
 
+  // Ignore all dbg_value intrinsics.
+  const IntrinsicInst *II = dyn_cast<IntrinsicInst>(&Inst);
+  if (II && II->getIntrinsicID() == Intrinsic::dbg_value) {
+    return std::error_code();
+  }
+
   const DILocation *DIL = DLoc;
   unsigned Lineno = DLoc.getLine();
   unsigned HeaderLineno = DIL->getScope()->getSubprogram()->getLine();
@@ -475,6 +482,14 @@
                  << Inst << " (line offset: " << Lineno - HeaderLineno << "."
                  << DIL->getDiscriminator() << " - weight: " << R.get()
                  << ")\n");
+  } else {
+    // If a call instruction is inlined in profile, but not inlined here,
+    // it means that the inlined callsite has no sample, thus the call
+    // instruction should have 0 count.
+    const CallInst *CI = dyn_cast<CallInst>(&Inst);
+    if (CI && findCalleeFunctionSamples(*CI)) {
+      R = 0;
+    }
   }
   return R;
 }


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