[PATCH] D84378: [PGO] Fix incorrect function entry count

[Rong Xu via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG1dd39b113313: [PGO] Fix incorrect function entry count (authored by xur).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D84378/new/

https://reviews.llvm.org/D84378

Files:
  llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
  llvm/test/Transforms/PGOProfile/Inputs/fix_entry_count.proftext
  llvm/test/Transforms/PGOProfile/fix_entry_count.ll


Index: llvm/test/Transforms/PGOProfile/fix_entry_count.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/PGOProfile/fix_entry_count.ll
@@ -0,0 +1,34 @@
+; RUN: llvm-profdata merge %S/Inputs/fix_entry_count.proftext -o %t.profdata
+; RUN: opt < %s -pgo-instr-use -pgo-instrument-entry=true -pgo-test-profile-file=%t.profdata -S | FileCheck %s --check-prefix=USE
+; RUN: opt < %s -passes=pgo-instr-use -pgo-instrument-entry=true -pgo-test-profile-file=%t.profdata -S | FileCheck %s --check-prefix=USE
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @test_simple_for(i32 %n) {
+; USE: define i32 @test_simple_for(i32 %n)
+; USE-SAME: !prof ![[ENTRY_COUNT:[0-9]*]]
+entry:
+  br label %for.cond
+
+for.cond:
+  %i = phi i32 [ 0, %entry ], [ %inc1, %for.inc ]
+  %sum = phi i32 [ 1, %entry ], [ %inc, %for.inc ]
+  %cmp = icmp slt i32 %i, %n
+  br i1 %cmp, label %for.body, label %for.end
+; USE: br i1 %cmp, label %for.body, label %for.end
+; USE-SAME: !prof ![[BW_FOR_COND:[0-9]+]]
+
+for.body:
+  %inc = add nsw i32 %sum, 1
+  br label %for.inc
+
+for.inc:
+  %inc1 = add nsw i32 %i, 1
+  br label %for.cond
+
+for.end:
+  ret i32 %sum
+}
+; USE: ![[ENTRY_COUNT]] = !{!"function_entry_count", i64 1}
+; USE: ![[BW_FOR_COND]] = !{!"branch_weights", i32 96, i32 1}
Index: llvm/test/Transforms/PGOProfile/Inputs/fix_entry_count.proftext
===================================================================
--- /dev/null
+++ llvm/test/Transforms/PGOProfile/Inputs/fix_entry_count.proftext
@@ -0,0 +1,8 @@
+:ir
+:entry_first
+test_simple_for
+34137660316
+2
+0
+96
+
Index: llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -1131,11 +1131,18 @@
   if (NumCounters != CountFromProfile.size()) {
     return false;
   }
+  auto *FuncEntry = &*F.begin();
+
   // Set the profile count to the Instrumented BBs.
   uint32_t I = 0;
   for (BasicBlock *InstrBB : InstrumentBBs) {
     uint64_t CountValue = CountFromProfile[I++];
     UseBBInfo &Info = getBBInfo(InstrBB);
+    // If we reach here, we know that we have some nonzero count
+    // values in this function. The entry count should not be 0.
+    // Fix it if necessary.
+    if (InstrBB == FuncEntry && CountValue == 0)
+      CountValue = 1;
     Info.setBBInfoCount(CountValue);
   }
   ProfileCountSize = CountFromProfile.size();
@@ -1326,7 +1333,6 @@
   }
 #endif
   uint64_t FuncEntryCount = getBBInfo(&*F.begin()).CountValue;
-  F.setEntryCount(ProfileCount(FuncEntryCount, Function::PCT_Real));
   uint64_t FuncMaxCount = FuncEntryCount;
   for (auto &BB : F) {
     auto BI = findBBInfo(&BB);
@@ -1334,6 +1340,11 @@
       continue;
     FuncMaxCount = std::max(FuncMaxCount, BI->CountValue);
   }
+
+  // Fix the obviously inconsistent entry count.
+  if (FuncMaxCount > 0 && FuncEntryCount == 0)
+    FuncEntryCount = 1;
+  F.setEntryCount(ProfileCount(FuncEntryCount, Function::PCT_Real));
   markFunctionAttributes(FuncEntryCount, FuncMaxCount);
 
   // Now annotate select instructions


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