[argprom] Assessing impact of number of arguments promoted on compiler performance

[teamiceberg]

Summary

Our initial hypothesis is that changes to the magic value of max_elements in argumentpromotion.cpp file can
lead to changes in compiler performance. To assess such changes, we have to introduce a global variable in the argumentpromotion.h header file. Then, we supply different values for this global variable by having a command line flag (-numargspromoted) bound to this global variable via the cl::opt interface. Initial analysis of compiler performance using the built in test suite demonstrate some significant changes in compile time as well as run time.
However, we are in the process of validating if these changes are real or just noise induced by other means. More experiments and sample runs need to be run, to be sure. However, we are setting up this initial patch as a way to learn how to setup a pipeline to enable the use of global variables to simulate magic values. Also, we are designing LIT tests to ensure that we submit a patch that conforms to built-in argument promotion tests in llvm/test folder.

[lebedev.ri]

Why is there a limit in the first place?

[teamiceberg]

I am putting up a fresh baseline. Thanks.

[teamiceberg]

reopen to test update

[teamiceberg]

update

[teamiceberg]

Better to open a new revision.

llvm/lib/Transforms/IPO/ArgumentPromotion.cpp

 //===- ArgumentPromotion.cpp - Promote by-reference arguments -------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //

 #include <string>
 #include <utility>
 #include <vector>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "argpromotion"
 
-<<<<<<< HEAD
 //opt flag to capture user supplied value for GV: GL_NUMPROMARGS
 cl::opt<unsigned, true> argmax("numargspromoted", cl::desc("Specify number of args to promote"), cl::value_desc("numargs"), cl::location(llvm::GL_NUMPROMARGS));
-=======
-cl::opt<unsigned, true> argmax("maxar", cl::Required, cl::desc("Specify number of args to promote"), cl::value_desc("maxargs"), cl::location(llvm::GL_MAXARGS));
->>>>>>> df0f0e791671d16f15d67c1f265b75f5a35a7624
 
 STATISTIC(NumArgumentsPromoted, "Number of pointer arguments promoted");
 STATISTIC(NumAggregatesPromoted, "Number of aggregate arguments promoted");
 STATISTIC(NumByValArgsPromoted, "Number of byval arguments promoted");
 STATISTIC(NumArgumentsDead, "Number of dead pointer args eliminated");
 
 /// A vector used to hold the indices of a single GEP instruction
 using IndicesVector = std::vector<uint64_t>;

 
 namespace {
 
 /// ArgPromotion - The 'by reference' to 'by value' argument promotion pass.
 struct ArgPromotion : public CallGraphSCCPass {
   // Pass identification, replacement for typeid
   static char ID;
 
-  explicit ArgPromotion(unsigned MaxElements = 3)
+  explicit ArgPromotion(unsigned MaxElements = GL_NUMPROMARGS)
       : CallGraphSCCPass(ID), MaxElements(MaxElements) {
     initializeArgPromotionPass(*PassRegistry::getPassRegistry());
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<AssumptionCacheTracker>();
     AU.addRequired<TargetLibraryInfoWrapperPass>();
     AU.addRequired<TargetTransformInfoWrapperPass>();

 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
 INITIALIZE_PASS_END(ArgPromotion, "argpromotion",
                     "Promote 'by reference' arguments to scalars", false, false)
 
 Pass *llvm::createArgumentPromotionPass(unsigned MaxElements) {
-<<<<<<< HEAD
   return new ArgPromotion(GL_NUMPROMARGS);
-=======
-  return new ArgPromotion(GL_MAXARGS);
->>>>>>> df0f0e791671d16f15d67c1f265b75f5a35a7624
 }
 
 bool ArgPromotion::runOnSCC(CallGraphSCC &SCC) {
   if (skipSCC(SCC))
     return false;
 
   // Get the callgraph information that we need to update to reflect our
   // changes.

llvm/test/Transforms/ArgumentPromotion/args-aggregates-mix-promote.ll

+; ModuleID = '/Users/shivamacpro/Desktop/EducationandProjects/GSOC2020/testprograms/mixed-args.cpp'
+source_filename = "/Users/shivamacpro/Desktop/EducationandProjects/GSOC2020/testprograms/mixed-args.cpp"
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.15.0"
+
+%struct.twomem = type { i32, i32 }
+%struct.threemem = type { i32, i32, i32 }
+%struct.fourmem = type { i32, i32, i32, i32 }
+
+; Function Attrs: noinline norecurse ssp uwtable
+define i32 @main() #0 {
+entry:
+  %retval = alloca i32, align 4
+  %tw = alloca %struct.twomem, align 4
+  %th = alloca %struct.threemem, align 4
+  %fo = alloca %struct.fourmem, align 4
+  %one = alloca i32, align 4
+  %two = alloca i32, align 4
+  %T = alloca i32, align 4
+  store i32 0, i32* %retval, align 4
+  %a = getelementptr inbounds %struct.twomem, %struct.twomem* %tw, i32 0, i32 0
+  store i32 1, i32* %a, align 4
+  %b = getelementptr inbounds %struct.twomem, %struct.twomem* %tw, i32 0, i32 1
+  store i32 2, i32* %b, align 4
+  %a1 = getelementptr inbounds %struct.threemem, %struct.threemem* %th, i32 0, i32 0
+  store i32 3, i32* %a1, align 4
+  %b2 = getelementptr inbounds %struct.threemem, %struct.threemem* %th, i32 0, i32 1
+  store i32 4, i32* %b2, align 4
+  %c = getelementptr inbounds %struct.threemem, %struct.threemem* %th, i32 0, i32 2
+  store i32 5, i32* %c, align 4
+  %a3 = getelementptr inbounds %struct.fourmem, %struct.fourmem* %fo, i32 0, i32 0
+  store i32 6, i32* %a3, align 4
+  %b4 = getelementptr inbounds %struct.fourmem, %struct.fourmem* %fo, i32 0, i32 1
+  store i32 7, i32* %b4, align 4
+  %c5 = getelementptr inbounds %struct.fourmem, %struct.fourmem* %fo, i32 0, i32 2
+  store i32 8, i32* %c5, align 4
+  %c6 = getelementptr inbounds %struct.fourmem, %struct.fourmem* %fo, i32 0, i32 2
+  store i32 9, i32* %c6, align 4
+  store i32 8, i32* %one, align 4
+  store i32 9, i32* %two, align 4
+  %call = call i32 @_ZL6calleePiS_P6twomemP8threememP7fourmem(i32* %one, i32* %two, %struct.twomem* %tw, %struct.threemem* %th, %struct.fourmem* %fo)
+  store i32 %call, i32* %T, align 4
+  ret i32 0
+}
+
+; Function Attrs: noinline nounwind ssp uwtable
+define internal i32 @_ZL6calleePiS_P6twomemP8threememP7fourmem(i32* %A, i32* %B, %struct.twomem* %TW, %struct.threemem* %TH, %struct.fourmem* %FO) #1 {
+entry:
+  %A.addr = alloca i32*, align 8
+  %B.addr = alloca i32*, align 8
+  %TW.addr = alloca %struct.twomem*, align 8
+  %TH.addr = alloca %struct.threemem*, align 8
+  %FO.addr = alloca %struct.fourmem*, align 8
+  %S = alloca i32, align 4
+  store i32* %A, i32** %A.addr, align 8
+  store i32* %B, i32** %B.addr, align 8
+  store %struct.twomem* %TW, %struct.twomem** %TW.addr, align 8
+  store %struct.threemem* %TH, %struct.threemem** %TH.addr, align 8
+  store %struct.fourmem* %FO, %struct.fourmem** %FO.addr, align 8
+  %0 = load i32*, i32** %A.addr, align 8
+  %1 = load i32, i32* %0, align 4
+  %2 = load i32*, i32** %B.addr, align 8
+  %3 = load i32, i32* %2, align 4
+  %add = add nsw i32 %1, %3
+  %4 = load %struct.twomem*, %struct.twomem** %TW.addr, align 8
+  %a = getelementptr inbounds %struct.twomem, %struct.twomem* %4, i32 0, i32 0
+  %5 = load i32, i32* %a, align 4
+  %add1 = add nsw i32 %add, %5
+  %6 = load %struct.twomem*, %struct.twomem** %TW.addr, align 8
+  %b = getelementptr inbounds %struct.twomem, %struct.twomem* %6, i32 0, i32 1
+  %7 = load i32, i32* %b, align 4
+  %add2 = add nsw i32 %add1, %7
+  %8 = load %struct.threemem*, %struct.threemem** %TH.addr, align 8
+  %a3 = getelementptr inbounds %struct.threemem, %struct.threemem* %8, i32 0, i32 0
+  %9 = load i32, i32* %a3, align 4
+  %add4 = add nsw i32 %add2, %9
+  %10 = load %struct.threemem*, %struct.threemem** %TH.addr, align 8
+  %b5 = getelementptr inbounds %struct.threemem, %struct.threemem* %10, i32 0, i32 1
+  %11 = load i32, i32* %b5, align 4
+  %add6 = add nsw i32 %add4, %11
+  %12 = load %struct.threemem*, %struct.threemem** %TH.addr, align 8
+  %c = getelementptr inbounds %struct.threemem, %struct.threemem* %12, i32 0, i32 2
+  %13 = load i32, i32* %c, align 4
+  %add7 = add nsw i32 %add6, %13
+  %14 = load %struct.fourmem*, %struct.fourmem** %FO.addr, align 8
+  %a8 = getelementptr inbounds %struct.fourmem, %struct.fourmem* %14, i32 0, i32 0
+  %15 = load i32, i32* %a8, align 4
+  %add9 = add nsw i32 %add7, %15
+  %16 = load %struct.fourmem*, %struct.fourmem** %FO.addr, align 8
+  %b10 = getelementptr inbounds %struct.fourmem, %struct.fourmem* %16, i32 0, i32 1
+  %17 = load i32, i32* %b10, align 4
+  %add11 = add nsw i32 %add9, %17
+  %18 = load %struct.fourmem*, %struct.fourmem** %FO.addr, align 8
+  %c12 = getelementptr inbounds %struct.fourmem, %struct.fourmem* %18, i32 0, i32 2
+  %19 = load i32, i32* %c12, align 4
+  %add13 = add nsw i32 %add11, %19
+  %20 = load %struct.fourmem*, %struct.fourmem** %FO.addr, align 8
+  %d = getelementptr inbounds %struct.fourmem, %struct.fourmem* %20, i32 0, i32 3
+  %21 = load i32, i32* %d, align 4
+  %add14 = add nsw i32 %add13, %21
+  store i32 %add14, i32* %S, align 4
+  %22 = load i32, i32* %S, align 4
+  ret i32 %22
+}
+
+attributes #0 = { noinline norecurse ssp uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cx16,+cx8,+fxsr,+mmx,+sahf,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { noinline nounwind ssp uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cx16,+cx8,+fxsr,+mmx,+sahf,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.module.flags = !{!0, !1}
+!llvm.ident = !{!2}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 7, !"PIC Level", i32 2}
+!2 = !{!"clang version 11.0.0 (https://github.com/teamiceberg/llvm-project.git 1fb9041df0182c3e582bfcb5875e6af743eab0a1)"}

llvm/test/Transforms/ArgumentPromotion/fourmember-struct-promote.ll

+; ModuleID = '/Users/shivamacpro/Desktop/EducationandProjects/GSOC2020/testprograms/fourmem-struct.cpp'
+source_filename = "/Users/shivamacpro/Desktop/EducationandProjects/GSOC2020/testprograms/fourmem-struct.cpp"
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.15.0"
+
+%struct.fourmem = type { i32, i32, i32, i32 }
+
+; Function Attrs: noinline norecurse ssp uwtable
+define i32 @main() #0 {
+entry:
+  %retval = alloca i32, align 4
+  %four = alloca %struct.fourmem, align 4
+  %T = alloca i32, align 4
+  store i32 0, i32* %retval, align 4
+  %a = getelementptr inbounds %struct.fourmem, %struct.fourmem* %four, i32 0, i32 0
+  store i32 1, i32* %a, align 4
+  %b = getelementptr inbounds %struct.fourmem, %struct.fourmem* %four, i32 0, i32 1
+  store i32 2, i32* %b, align 4
+  %c = getelementptr inbounds %struct.fourmem, %struct.fourmem* %four, i32 0, i32 2
+  store i32 3, i32* %c, align 4
+  %d = getelementptr inbounds %struct.fourmem, %struct.fourmem* %four, i32 0, i32 3
+  store i32 4, i32* %d, align 4
+  %call = call i32 @_ZL6calleeP7fourmem(%struct.fourmem* %four)
+  store i32 %call, i32* %T, align 4
+  ret i32 0
+}
+
+; Function Attrs: noinline nounwind ssp uwtable
+define internal i32 @_ZL6calleeP7fourmem(%struct.fourmem* %t) #1 {
+entry:
+  %t.addr = alloca %struct.fourmem*, align 8
+  %S = alloca i32, align 4
+  store %struct.fourmem* %t, %struct.fourmem** %t.addr, align 8
+  %0 = load %struct.fourmem*, %struct.fourmem** %t.addr, align 8
+  %a = getelementptr inbounds %struct.fourmem, %struct.fourmem* %0, i32 0, i32 0
+  %1 = load i32, i32* %a, align 4
+  %2 = load %struct.fourmem*, %struct.fourmem** %t.addr, align 8
+  %b = getelementptr inbounds %struct.fourmem, %struct.fourmem* %2, i32 0, i32 1
+  %3 = load i32, i32* %b, align 4
+  %add = add nsw i32 %1, %3
+  %4 = load %struct.fourmem*, %struct.fourmem** %t.addr, align 8
+  %c = getelementptr inbounds %struct.fourmem, %struct.fourmem* %4, i32 0, i32 2
+  %5 = load i32, i32* %c, align 4
+  %add1 = add nsw i32 %add, %5
+  %6 = load %struct.fourmem*, %struct.fourmem** %t.addr, align 8
+  %d = getelementptr inbounds %struct.fourmem, %struct.fourmem* %6, i32 0, i32 3
+  %7 = load i32, i32* %d, align 4
+  %add2 = add nsw i32 %add1, %7
+  store i32 %add2, i32* %S, align 4
+  %8 = load i32, i32* %S, align 4
+  ret i32 %8
+}
+
+attributes #0 = { noinline norecurse ssp uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cx16,+cx8,+fxsr,+mmx,+sahf,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { noinline nounwind ssp uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cx16,+cx8,+fxsr,+mmx,+sahf,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.module.flags = !{!0, !1}
+!llvm.ident = !{!2}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 7, !"PIC Level", i32 2}
+!2 = !{!"clang version 11.0.0 (https://github.com/teamiceberg/llvm-project.git 1fb9041df0182c3e582bfcb5875e6af743eab0a1)"}