[InstrProf] Support conditional counter updates for integer counters #109222
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In llvm#102542. conditional counter updates were only implemented for boolean counters. This PR implements conditional counter updates for integer counters. When the flag -conditional-counter-update is set, integer counters are now treated like boolean counters - @llvm.instrprof.update now checks whether or not a counter is zero, and if not, writes 1 to it. The motiviation for this mode is that we can bring the benefits of conditional single byte counter updates to languages whose frontends do not support single byte counters (e.g. Rust).
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@llvm/pr-subscribers-llvm-transforms @llvm/pr-subscribers-pgo Author: Alan Zhao (alanzhao1) ChangesIn #102542. conditional counter updates were only implemented for boolean counters. This PR implements conditional counter updates for integer counters. When the flag -conditional-counter-update is set, integer counters are now treated like boolean counters - @llvm.instrprof.update now checks whether or not a counter is zero, and if not, writes 1 to it. The motiviation for this mode is that we can bring the benefits of conditional single byte counter updates to languages whose frontends do not support single byte counters (e.g. Rust). Full diff: https://github.com/llvm/llvm-project/pull/109222.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
index 014e049ed0d8e5..9d5394deda0856 100644
--- a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -1263,8 +1263,20 @@ void InstrLowerer::lowerIncrement(InstrProfIncrementInst *Inc) {
MaybeAlign(), AtomicOrdering::Monotonic);
} else {
Value *IncStep = Inc->getStep();
- Value *Load = Builder.CreateLoad(IncStep->getType(), Addr, "pgocount");
- auto *Count = Builder.CreateAdd(Load, Inc->getStep());
+ auto *CtrTy = IncStep->getType();
+ Value *Load = Builder.CreateLoad(CtrTy, Addr, "pgocount");
+ Value *Count;
+
+ if (ConditionalCounterUpdate) {
+ Instruction *SplitBefore = Inc->getNextNode();
+ Value *Cmp = Builder.CreateIsNull(Load, "pgocount.ifzero");
+ Instruction *ThenBranch =
+ SplitBlockAndInsertIfThen(Cmp, SplitBefore, false);
+ Builder.SetInsertPoint(ThenBranch);
+ Count = ConstantInt::get(CtrTy, 1);
+ } else {
+ Count = Builder.CreateAdd(Load, Inc->getStep());
+ }
auto *Store = Builder.CreateStore(Count, Addr);
if (isCounterPromotionEnabled())
PromotionCandidates.emplace_back(cast<Instruction>(Load), Store);
diff --git a/llvm/test/Instrumentation/InstrProfiling/conditional-counter-updates.ll b/llvm/test/Instrumentation/InstrProfiling/conditional-counter-updates.ll
index 998443ec0cd568..ebd510cfb5f08a 100644
--- a/llvm/test/Instrumentation/InstrProfiling/conditional-counter-updates.ll
+++ b/llvm/test/Instrumentation/InstrProfiling/conditional-counter-updates.ll
@@ -5,6 +5,9 @@ target triple = "x86_64-unknown-linux-gnu"
@__profn_foo = private constant [3 x i8] c"foo"
@__profn_bar = private constant [3 x i8] c"bar"
+@__profn_fooint = private constant [6 x i8] c"fooint"
+@__profn_barint = private constant [6 x i8] c"barint"
+
; CHECK-LABEL: define void @foo
; CHECK-NEXT: %pgocount = load i8, ptr @__profc_foo, align 1
; CHECK-NEXT: %pgocount.ifnonzero = icmp ne i8 %pgocount, 0
@@ -67,3 +70,91 @@ return: ; preds = %if.end, %if.then
%1 = load i32, ptr %retval, align 4
ret i32 %1
}
+
+; CHECK-LABEL: define void @fooint
+; CHECK-NEXT: %pgocount = load i64, ptr @__profc_fooint, align 8
+; CHECK-NEXT: %pgocount.ifzero = icmp eq i64 %pgocount, 0
+; CHECK-NEXT: br i1 %pgocount.ifzero, label %1, label %2
+
+; CHECK-LABEL: 1:
+; CHECK-NEXT: store i64 1, ptr @__profc_fooint, align 8
+; CHECK-NEXT: br label %2
+
+; CHECK-LABEL: 2:
+; CHECK-NEXT: ret void
+define void @fooint() {
+ call void @llvm.instrprof.increment(ptr @__profn_fooint, i64 0, i32 1, i32 0)
+ ret void
+}
+
+; CHECK-LABEL: define i32 @barint
+; CHECK-LABEL: entry:
+; CHECK-NEXT: %retval = alloca i32, align 4
+; CHECK-NEXT: %cond.addr = alloca i32, align 4
+; CHECK-NEXT: store i32 %cond, ptr %cond.addr, align 4
+; CHECK-NEXT: %pgocount = load i64, ptr @__profc_barint, align 8
+; CHECK-NEXT: %pgocount.ifzero = icmp eq i64 %pgocount, 0
+; CHECK-NEXT: br i1 %pgocount.ifzero, label %0, label %1
+
+; CHECK-LABEL: 0: ; preds = %entry
+; CHECK-NEXT: store i64 1, ptr @__profc_barint, align 8
+; CHECK-NEXT: br label %1
+
+; CHECK-LABEL: 1: ; preds = %entry, %0
+; CHECK-NEXT: %2 = load i32, ptr %cond.addr, align 4
+; CHECK-NEXT: %cmp = icmp slt i32 %2, 0
+; CHECK-NEXT: br i1 %cmp, label %if.then, label %if.end
+
+; CHECK-LABEL: if.then: ; preds = %1
+; CHECK-NEXT: %pgocount1 = load i64, ptr getelementptr inbounds ([3 x i64], ptr @__profc_barint, i32 0, i32 1), align 8
+; CHECK-NEXT: %pgocount.ifzero2 = icmp eq i64 %pgocount1, 0
+; CHECK-NEXT: br i1 %pgocount.ifzero2, label %3, label %4
+
+; CHECK-LABEL: 3: ; preds = %if.then
+; CHECK-NEXT: store i64 1, ptr getelementptr inbounds ([3 x i64], ptr @__profc_barint, i32 0, i32 1), align 8
+; CHECK-NEXT: br label %4
+;
+; CHECK-LABEL: 4: ; preds = %if.then, %3
+; CHECK-NEXT: store i32 -1, ptr %retval, align 4
+; CHECK-NEXT: br label %return
+;
+; CHECK-LABEL: if.end: ; preds = %1
+; CHECK-NEXT: %pgocount3 = load i64, ptr getelementptr inbounds ([3 x i64], ptr @__profc_barint, i32 0, i32 2), align 8
+; CHECK-NEXT: %pgocount.ifzero4 = icmp eq i64 %pgocount3, 0
+; CHECK-NEXT: br i1 %pgocount.ifzero4, label %5, label %6
+;
+; CHECK-LABEL: 5: ; preds = %if.end
+; CHECK-NEXT: store i64 1, ptr getelementptr inbounds ([3 x i64], ptr @__profc_barint, i32 0, i32 2), align 8
+; CHECK-NEXT: br label %6
+;
+; CHECK-LABEL: 6: ; preds = %if.end, %5
+; CHECK-NEXT: store i32 0, ptr %retval, align 4
+; CHECK-NEXT: br label %return
+;
+; CHECK-LABEL: return: ; preds = %6, %4
+; CHECK-NEXT: %7 = load i32, ptr %retval, align 4
+; CHECK-NEXT: ret i32 %7
+define i32 @barint(i32 %cond) #0 {
+entry:
+ %retval = alloca i32, align 4
+ %cond.addr = alloca i32, align 4
+ store i32 %cond, ptr %cond.addr, align 4
+ call void @llvm.instrprof.increment(ptr @__profn_barint, i64 0, i32 3, i32 0)
+ %0 = load i32, ptr %cond.addr, align 4
+ %cmp = icmp slt i32 %0, 0
+ br i1 %cmp, label %if.then, label %if.end
+
+if.then: ; preds = %entry
+ call void @llvm.instrprof.increment(ptr @__profn_barint, i64 0, i32 3, i32 1)
+ store i32 -1, ptr %retval, align 4
+ br label %return
+
+if.end: ; preds = %entry
+ call void @llvm.instrprof.increment(ptr @__profn_barint, i64 0, i32 3, i32 2)
+ store i32 0, ptr %retval, align 4
+ br label %return
+
+return: ; preds = %if.end, %if.then
+ %1 = load i32, ptr %retval, align 4
+ ret i32 %1
+}
\ No newline at end of file
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petrhosek
reviewed
Sep 19, 2024
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I'm going to close this as I just realized this won't work. Say for example we have foo() // counter 0
if (...)
bar(); // counter 1
else;
baz(); // counter 0 - 1Clang doesn't insert counters for each branch of an |
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In #102542. conditional counter updates were only implemented for boolean counters. This PR implements conditional counter updates for integer counters. When the flag -conditional-counter-update is set, integer counters are now treated like boolean counters - @llvm.instrprof.update now checks whether or not a counter is zero, and if not, writes 1 to it.
The motiviation for this mode is that we can bring the benefits of conditional single byte counter updates to languages whose frontends do not support single byte counters (e.g. Rust).