[llvm] r289521 - [PGO] Fix insane counts due to nonreturn calls

[Rong Xu via llvm-commits]

Author: xur
Date: Tue Dec 13 00:41:14 2016
New Revision: 289521

URL: http://llvm.org/viewvc/llvm-project?rev=289521&view=rev
Log:
[PGO] Fix insane counts due to nonreturn calls

Summary:
Since we don't break BBs for function calls. We might get some insane counts 
(wrap of unsigned) in the presence of noreturn calls.

This patch sets these counts to zero instead of the wrapped number.

Reviewers: davidxl

Subscribers: xur, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D27602

Added:
    llvm/trunk/test/Transforms/PGOProfile/Inputs/noreturncall.proftext
    llvm/trunk/test/Transforms/PGOProfile/noreturncall.ll
Modified:
    llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp

Modified: llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp?rev=289521&r1=289520&r2=289521&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp Tue Dec 13 00:41:14 2016
@@ -884,12 +884,21 @@ void PGOUseFunc::populateCounters() {
       }
       if (Count->CountValid) {
         if (Count->UnknownCountOutEdge == 1) {
-          uint64_t Total = Count->CountValue - sumEdgeCount(Count->OutEdges);
+          uint64_t Total = 0;
+          uint64_t OutSum = sumEdgeCount(Count->OutEdges);
+          // If the one of the successor block can early terminate (no-return),
+          // we can end up with situation where out edge sum count is larger as
+          // the source BB's count is collected by a post-dominated block.
+          if (Count->CountValue > OutSum)
+            Total = Count->CountValue - OutSum;
           setEdgeCount(Count->OutEdges, Total);
           Changes = true;
         }
         if (Count->UnknownCountInEdge == 1) {
-          uint64_t Total = Count->CountValue - sumEdgeCount(Count->InEdges);
+          uint64_t Total = 0;
+          uint64_t InSum = sumEdgeCount(Count->InEdges);
+          if (Count->CountValue > InSum)
+            Total = Count->CountValue - InSum;
           setEdgeCount(Count->InEdges, Total);
           Changes = true;
         }

Added: llvm/trunk/test/Transforms/PGOProfile/Inputs/noreturncall.proftext
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/PGOProfile/Inputs/noreturncall.proftext?rev=289521&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/PGOProfile/Inputs/noreturncall.proftext (added)
+++ llvm/trunk/test/Transforms/PGOProfile/Inputs/noreturncall.proftext Tue Dec 13 00:41:14 2016
@@ -0,0 +1,11 @@
+# IR level Instrumentation Flag
+:ir
+foo
+# Func Hash:
+36496524737
+# Num Counters:
+3
+# Counter Values:
+20
+21
+0

Added: llvm/trunk/test/Transforms/PGOProfile/noreturncall.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/PGOProfile/noreturncall.ll?rev=289521&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/PGOProfile/noreturncall.ll (added)
+++ llvm/trunk/test/Transforms/PGOProfile/noreturncall.ll Tue Dec 13 00:41:14 2016
@@ -0,0 +1,46 @@
+; RUN: llvm-profdata merge %S/Inputs/noreturncall.proftext -o %t.profdata
+; RUN: opt < %s -pgo-instr-use -pgo-test-profile-file=%t.profdata -S -debug-only=pgo-instrumentation 2>&1 | FileCheck %s --check-prefix=USE
+; RUN: opt < %s -passes=pgo-instr-use -pgo-test-profile-file=%t.profdata -S -debug-only=pgo-instrumentation 2>&1 | FileCheck %s --check-prefix=USE
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare i32 @bar0(i32)
+
+define i32 @bar2(i32 %i) {
+entry:
+  unreachable
+}
+
+define i32 @foo(i32 %i, i32 %j, i32 %k) {
+entry:
+  %cmp = icmp slt i32 %i, 999
+  br i1 %cmp, label %if.then, label %if.end
+
+if.then:
+  %call = call i32 @bar0(i32 %i)
+  br label %if.end
+
+if.end:
+  %ret.0 = phi i32 [ %call, %if.then ], [ 0, %entry ]
+  %cmp1 = icmp sgt i32 %j, 1000
+  %cmp3 = icmp sgt i32 %k, 99
+  %or.cond = and i1 %cmp1, %cmp3
+  br i1 %or.cond, label %if.then4, label %if.end7
+
+if.then4:
+  %call5 = call i32 @bar2(i32 undef)
+  br label %if.end7
+
+if.end7:
+  %mul = mul nsw i32 %ret.0, %ret.0
+  ret i32 %mul
+}
+; USE:  Edge 0: 1-->3  c  W=8000  Count=0
+; USE:  Edge 1: 3-->5  c  W=8000  Count=20
+; USE:  Edge 2: 0-->1     W=16  Count=21
+; USE:  Edge 3: 5-->0 *   W=16  Count=20
+; USE:  Edge 4: 1-->2     W=8  Count=21
+; USE:  Edge 5: 2-->3 *   W=8  Count=21
+; USE:  Edge 6: 3-->4     W=8  Count=0
+; USE:  Edge 7: 4-->5 *   W=8  Count=0