[llvm] 793b481 - [CGProfile] Don't emit call graph profile edges with zero weight

[Nico Weber via llvm-commits]

Author: Leonard Grey
Date: 2021-10-28T11:32:49-04:00
New Revision: 793b481f54f8343bc3e6041f4400fe54166529a9

URL: https://github.com/llvm/llvm-project/commit/793b481f54f8343bc3e6041f4400fe54166529a9
DIFF: https://github.com/llvm/llvm-project/commit/793b481f54f8343bc3e6041f4400fe54166529a9.diff

LOG: [CGProfile] Don't emit call graph profile edges with zero weight

With D112160 and D112164, on a Chrome Mac build this reduces the total
size of CGProfile sections by 78% (around 25% eliminated entirely) and
total size of object files by 0.14%.

Differential Revision: https://reviews.llvm.org/D112655

Added: 
    

Modified: 
    llvm/lib/Transforms/Instrumentation/CGProfile.cpp
    llvm/test/Instrumentation/cgprofile.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Instrumentation/CGProfile.cpp b/llvm/lib/Transforms/Instrumentation/CGProfile.cpp
index 9acd82c005e61..1a7f7a365ce4b 100644
--- a/llvm/lib/Transforms/Instrumentation/CGProfile.cpp
+++ b/llvm/lib/Transforms/Instrumentation/CGProfile.cpp
@@ -53,6 +53,8 @@ static bool runCGProfilePass(
   InstrProfSymtab Symtab;
   auto UpdateCounts = [&](TargetTransformInfo &TTI, Function *F,
                           Function *CalledF, uint64_t NewCount) {
+    if (NewCount == 0)
+      return;
     if (!CalledF || !TTI.isLoweredToCall(CalledF) ||
         CalledF->hasDLLImportStorageClass())
       return;

diff  --git a/llvm/test/Instrumentation/cgprofile.ll b/llvm/test/Instrumentation/cgprofile.ll
index 8458b9949f320..5e2f2665ab0f4 100644
--- a/llvm/test/Instrumentation/cgprofile.ll
+++ b/llvm/test/Instrumentation/cgprofile.ll
@@ -14,6 +14,7 @@ declare i32 @func2()
 declare i32 @func3()
 declare i32 @func4()
 declare dllimport i32 @func5()
+declare i32 @func6()
 
 define void @freq(i1 %cond) !prof !1 {
   %tmp = load i32 ()*, i32 ()** @foo, align 8
@@ -29,7 +30,7 @@ B:
 
 !1 = !{!"function_entry_count", i64 32}
 !2 = !{!"branch_weights", i32 5, i32 10}
-!3 = !{!"VP", i32 0, i64 1600, i64 7651369219802541373, i64 1030, i64 -4377547752858689819, i64 410, i64 -6929281286627296573, i64 150, i64 -2545542355363006406, i64 10, i64 3667884930908592509, i64 0}
+!3 = !{!"VP", i32 0, i64 1600, i64 7651369219802541373, i64 1030, i64 -4377547752858689819, i64 410, i64 -6929281286627296573, i64 150, i64 -2545542355363006406, i64 10, i64 3667884930908592509, i64 1, i64 15435711456043681792, i64 0}
 
 ; CHECK: !llvm.module.flags = !{![[cgprof:[0-9]+]]}
 ; CHECK: ![[cgprof]] = !{i32 5, !"CG Profile", ![[prof:[0-9]+]]}
@@ -41,4 +42,5 @@ B:
 ; CHECK: ![[e4]] = !{void (i1)* @freq, i32 ()* @func1, i64 10}
 ; CHECK: ![[e5]] = !{void (i1)* @freq, void ()* @a, i64 11}
 ; CHECK: ![[e6]] = !{void (i1)* @freq, void ()* @b, i64 21}
-; CHECK-NOT: !{void (i1)* @freq, void ()* @func5, i64 0}
\ No newline at end of file
+; CHECK-NOT: !{void (i1)* @freq, void ()* @func5, i64 1}
+; CHECK-NOT: !{void (i1)* @freq, void ()* @func6, i64 0}