[llvm] r301645 - Memory intrinsic value profile optimization: Avoid divide by 0

[Teresa Johnson via llvm-commits]

Author: tejohnson
Date: Fri Apr 28 09:30:54 2017
New Revision: 301645

URL: http://llvm.org/viewvc/llvm-project?rev=301645&view=rev
Log:
Memory intrinsic value profile optimization: Avoid divide by 0

Summary:
Skip memops if the total value profiled count is 0, we can't correctly
scale up the counts and there is no point anyway.

Reviewers: davidxl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D32624

Added:
    llvm/trunk/test/Transforms/PGOProfile/memop_size_opt_zero.ll
Modified:
    llvm/trunk/lib/Transforms/Instrumentation/IndirectCallPromotion.cpp

Modified: llvm/trunk/lib/Transforms/Instrumentation/IndirectCallPromotion.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/IndirectCallPromotion.cpp?rev=301645&r1=301644&r2=301645&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/IndirectCallPromotion.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/IndirectCallPromotion.cpp Fri Apr 28 09:30:54 2017
@@ -872,6 +872,10 @@ bool MemOPSizeOpt::perform(MemIntrinsic
 
   if (ActualCount < MemOPCountThreshold)
     return false;
+  // Skip if the total value profiled count is 0, in which case we can't
+  // scale up the counts properly (and there is no profitable transformation).
+  if (TotalCount == 0)
+    return false;
 
   TotalCount = ActualCount;
   if (MemOPScaleCount)

Added: llvm/trunk/test/Transforms/PGOProfile/memop_size_opt_zero.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/PGOProfile/memop_size_opt_zero.ll?rev=301645&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/PGOProfile/memop_size_opt_zero.ll (added)
+++ llvm/trunk/test/Transforms/PGOProfile/memop_size_opt_zero.ll Fri Apr 28 09:30:54 2017
@@ -0,0 +1,19 @@
+; Test to ensure the pgo memop optimization pass doesn't try to scale
+; up a value profile with a 0 count, which would lead to divide by 0.
+; RUN: opt < %s -passes=pgo-memop-opt -pgo-memop-count-threshold=1 -S | FileCheck %s --check-prefix=MEMOP_OPT
+; RUN: opt < %s -pgo-memop-opt -pgo-memop-count-threshold=1 -S | FileCheck %s --check-prefix=MEMOP_OPT
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @foo(i8* %dst, i8* %src, i64 %conv) !prof !0 {
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %conv, i32 1, i1 false), !prof !1
+  ret void
+}
+
+; MEMOP_OPT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %conv, i32 1, i1 false), !prof !1
+
+!0 = !{!"function_entry_count", i64 1}
+!1 = !{!"VP", i32 1, i64 0, i64 1, i64 0, i64 2, i64 0, i64 3, i64 0, i64 9, i64 0, i64 4, i64 0, i64 5, i64 0, i64 6, i64 0, i64 7, i64 0, i64 8, i64 0}
+
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture readonly, i64, i32, i1)