[llvm] 3024fe5 - [CGSCC] Detect devirtualization in more cases
Arthur Eubanks via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 22 19:44:47 PDT 2020
Author: Arthur Eubanks
Date: 2020-10-22T19:44:22-07:00
New Revision: 3024fe5b55ed72633915f613bd5e2826583c396f
URL: https://github.com/llvm/llvm-project/commit/3024fe5b55ed72633915f613bd5e2826583c396f
DIFF: https://github.com/llvm/llvm-project/commit/3024fe5b55ed72633915f613bd5e2826583c396f.diff
LOG: [CGSCC] Detect devirtualization in more cases
The devirtualization wrapper misses cases where if it wraps a pass
manager, an individual pass may devirtualize an indirect call created by
a previous pass. For example, inlining may create a new indirect call
which is devirtualized by instcombine. Currently the devirtualization
wrapper will not see that because it only checks cgscc edges at the very
beginning and end of the pass (manager) it wraps.
This fixes some tests testing this exact behavior in the legacy PM.
This piggybacks off of updateCGAndAnalysisManagerForPass()'s detection
of promoted ref to call edges.
This supercedes one of the previous mechanisms to detect
devirtualization by keeping track of potentially promoted call
instructions via WeakTrackingVHs.
There is one more existing way of detecting devirtualization, by
checking if the number of indirect calls has decreased and the number of
direct calls has increased in a function. It handles cases where calls
to functions without definitions are promoted, and some tests rely on
that. LazyCallGraph doesn't track edges to functions without
definitions so this part can't be removed in this change.
check-llvm and check-clang with -abort-on-max-devirt-iterations-reached
on by default doesn't show any failures outside of tests specifically
testing it so it doesn't needlessly rerun passes more than necessary.
(The NPM -O2/3 pipeline run the inliner/function simplification pipeline
under a devirtualization repeater pass up to 4 times by default).
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D89587
Added:
llvm/test/Transforms/Inline/devirtualize-5.ll
Modified:
llvm/include/llvm/Analysis/CGSCCPassManager.h
llvm/lib/Analysis/CGSCCPassManager.cpp
llvm/test/Transforms/Inline/devirtualize-3.ll
llvm/test/Transforms/Inline/devirtualize.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/Analysis/CGSCCPassManager.h b/llvm/include/llvm/Analysis/CGSCCPassManager.h
index 755bc92ddccf..5f2e50e922c0 100644
--- a/llvm/include/llvm/Analysis/CGSCCPassManager.h
+++ b/llvm/include/llvm/Analysis/CGSCCPassManager.h
@@ -314,6 +314,9 @@ struct CGSCCUpdateResult {
/// for a better technique.
SmallDenseSet<std::pair<LazyCallGraph::Node *, LazyCallGraph::SCC *>, 4>
&InlinedInternalEdges;
+
+ /// If any calls in the current SCC were devirtualized.
+ bool Devirtualized;
};
/// The core module pass which does a post-order walk of the SCCs and
@@ -596,9 +599,6 @@ class DevirtSCCRepeatedPass
// a pointer that we can update.
LazyCallGraph::SCC *C = &InitialC;
- // Collect value handles for all of the indirect call sites.
- SmallVector<WeakTrackingVH, 8> CallHandles;
-
// Struct to track the counts of direct and indirect calls in each function
// of the SCC.
struct CallCount {
@@ -608,10 +608,7 @@ class DevirtSCCRepeatedPass
// Put value handles on all of the indirect calls and return the number of
// direct calls for each function in the SCC.
- auto ScanSCC = [](LazyCallGraph::SCC &C,
- SmallVectorImpl<WeakTrackingVH> &CallHandles) {
- assert(CallHandles.empty() && "Must start with a clear set of handles.");
-
+ auto ScanSCC = [](LazyCallGraph::SCC &C) {
SmallDenseMap<Function *, CallCount> CallCounts;
CallCount CountLocal = {0, 0};
for (LazyCallGraph::Node &N : C) {
@@ -624,7 +621,6 @@ class DevirtSCCRepeatedPass
++Count.Direct;
} else {
++Count.Indirect;
- CallHandles.push_back(WeakTrackingVH(&I));
}
}
}
@@ -633,13 +629,14 @@ class DevirtSCCRepeatedPass
};
// Populate the initial call handles and get the initial call counts.
- auto CallCounts = ScanSCC(*C, CallHandles);
+ auto CallCounts = ScanSCC(*C);
for (int Iteration = 0;; ++Iteration) {
-
if (!PI.runBeforePass<LazyCallGraph::SCC>(Pass, *C))
continue;
+ UR.Devirtualized = false;
+
PreservedAnalyses PassPA = Pass.run(*C, AM, CG, UR);
if (UR.InvalidatedSCCs.count(C))
@@ -658,34 +655,12 @@ class DevirtSCCRepeatedPass
assert(!UR.InvalidatedSCCs.count(C) && "Processing an invalid SCC!");
assert(C->begin() != C->end() && "Cannot have an empty SCC!");
- // Check whether any of the handles were devirtualized.
- auto IsDevirtualizedHandle = [&](WeakTrackingVH &CallH) {
- if (!CallH)
- return false;
- auto *CB = dyn_cast<CallBase>(CallH);
- if (!CB)
- return false;
-
- // If the call is still indirect, leave it alone.
- Function *F = CB->getCalledFunction();
- if (!F)
- return false;
-
- LLVM_DEBUG(dbgs() << "Found devirtualized call from "
- << CB->getParent()->getParent()->getName() << " to "
- << F->getName() << "\n");
-
- // We now have a direct call where previously we had an indirect call,
- // so iterate to process this devirtualization site.
- return true;
- };
- bool Devirt = llvm::any_of(CallHandles, IsDevirtualizedHandle);
+ bool Devirt = UR.Devirtualized;
// Rescan to build up a new set of handles and count how many direct
// calls remain. If we decide to iterate, this also sets up the input to
// the next iteration.
- CallHandles.clear();
- auto NewCallCounts = ScanSCC(*C, CallHandles);
+ auto NewCallCounts = ScanSCC(*C);
// If we haven't found an explicit devirtualization already see if we
// have decreased the number of indirect calls and increased the number
@@ -790,7 +765,8 @@ ModuleToPostOrderCGSCCPassAdaptor<CGSCCPassT>::run(Module &M,
CGSCCUpdateResult UR = {
RCWorklist, CWorklist, InvalidRefSCCSet, InvalidSCCSet,
- nullptr, nullptr, PreservedAnalyses::all(), InlinedInternalEdges};
+ nullptr, nullptr, PreservedAnalyses::all(), InlinedInternalEdges,
+ false};
// Request PassInstrumentation from analysis manager, will use it to run
// instrumenting callbacks for the passes later.
diff --git a/llvm/lib/Analysis/CGSCCPassManager.cpp b/llvm/lib/Analysis/CGSCCPassManager.cpp
index 61c03f9bddfa..206088b7895f 100644
--- a/llvm/lib/Analysis/CGSCCPassManager.cpp
+++ b/llvm/lib/Analysis/CGSCCPassManager.cpp
@@ -666,6 +666,7 @@ static LazyCallGraph::SCC &updateCGAndAnalysisManagerForPass(
// Now promote ref edges into call edges.
for (Node *CallTarget : PromotedRefTargets) {
+ UR.Devirtualized = true;
SCC &TargetC = *G.lookupSCC(*CallTarget);
RefSCC &TargetRC = TargetC.getOuterRefSCC();
diff --git a/llvm/test/Transforms/Inline/devirtualize-3.ll b/llvm/test/Transforms/Inline/devirtualize-3.ll
index 4165b2125dfc..987463a03766 100644
--- a/llvm/test/Transforms/Inline/devirtualize-3.ll
+++ b/llvm/test/Transforms/Inline/devirtualize-3.ll
@@ -1,4 +1,5 @@
; RUN: opt -basic-aa -S -O2 < %s | FileCheck %s
+; RUN: opt -aa-pipeline=basic-aa -S -passes='default<O2>' < %s | FileCheck %s
; PR5009
; CHECK: define i32 @main()
diff --git a/llvm/test/Transforms/Inline/devirtualize-5.ll b/llvm/test/Transforms/Inline/devirtualize-5.ll
new file mode 100644
index 000000000000..359c8e183de4
--- /dev/null
+++ b/llvm/test/Transforms/Inline/devirtualize-5.ll
@@ -0,0 +1,22 @@
+; RUN: opt -abort-on-max-devirt-iterations-reached -passes='cgscc(devirt<2>(inline,instcombine))' -S < %s | FileCheck %s
+; RUN: opt -abort-on-max-devirt-iterations-reached -passes='default<O2>' -S < %s | FileCheck %s
+
+define i32 @i() alwaysinline {
+ ret i32 45
+}
+
+; CHECK-LABEL: define i32 @main
+; CHECK-NEXT: ret i32 45
+
+define i32 @main() {
+ %a = alloca i32 ()*
+ store i32 ()* @i, i32 ()** %a
+ %r = call i32 @call(i32 ()** %a)
+ ret i32 %r
+}
+
+define i32 @call(i32 ()** %a) alwaysinline {
+ %c = load i32 ()*, i32 ()** %a
+ %r = call i32 %c()
+ ret i32 %r
+}
diff --git a/llvm/test/Transforms/Inline/devirtualize.ll b/llvm/test/Transforms/Inline/devirtualize.ll
index 561bb62ae644..eaba1a8c19c5 100644
--- a/llvm/test/Transforms/Inline/devirtualize.ll
+++ b/llvm/test/Transforms/Inline/devirtualize.ll
@@ -1,4 +1,5 @@
; RUN: opt -S -Os < %s | FileCheck %s
+; RUN: opt -S -aa-pipeline=basic-aa -passes='default<Os>' < %s | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin10.0.0"
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