[llvm] [MemDep] Use EarliestEscapeInfo (PR #69727)
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Fri Oct 20 06:47:32 PDT 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Nikita Popov (nikic)
<details>
<summary>Changes</summary>
Use BatchAA with EarliestEscapeInfo instead of callCapturesBefore() in MemDepAnalysis. The advantage of this is that it will also take not-captured-before information into account for non-calls (see test_store_before_capture for a representative example), and that this is a cached analysis. The disadvantage is that EII is slightly less precise than full CapturedBefore analysis.
In practice the impact is positive, with gvn.NumGVNLoad going from 22022 to 22808 on test-suite. Full list of diffs: https://gist.github.com/nikic/9b6b4187d96d25249e9d874b47be99df
The impact to compile-time is also positive, mainly in the ThinLTO configuration: http://llvm-compile-time-tracker.com/compare.php?from=7c7896b1beeb1d275a06557111363b99b754398a&to=72a9442c743de0ad3fe84e2f8042f392aacda2c7&stat=instructions%3Au
---
Full diff: https://github.com/llvm/llvm-project/pull/69727.diff
4 Files Affected:
- (modified) llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h (+3-2)
- (modified) llvm/lib/Analysis/MemoryDependenceAnalysis.cpp (+5-7)
- (modified) llvm/test/CodeGen/BPF/CORE/no-narrow-load.ll (+4-4)
- (modified) llvm/test/Transforms/GVN/captured-before.ll (+1-2)
``````````diff
diff --git a/llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h b/llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h
index 27185aa9942e4e3..d5b2eb6253db959 100644
--- a/llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h
+++ b/llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h
@@ -18,6 +18,7 @@
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/PointerSumType.h"
#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/PredIteratorCache.h"
@@ -27,7 +28,6 @@
namespace llvm {
-class AAResults;
class AssumptionCache;
class BatchAAResults;
class DominatorTree;
@@ -356,6 +356,7 @@ class MemoryDependenceResults {
const TargetLibraryInfo &TLI;
DominatorTree &DT;
PredIteratorCache PredCache;
+ EarliestEscapeInfo EII;
unsigned DefaultBlockScanLimit;
@@ -367,7 +368,7 @@ class MemoryDependenceResults {
MemoryDependenceResults(AAResults &AA, AssumptionCache &AC,
const TargetLibraryInfo &TLI, DominatorTree &DT,
unsigned DefaultBlockScanLimit)
- : AA(AA), AC(AC), TLI(TLI), DT(DT),
+ : AA(AA), AC(AC), TLI(TLI), DT(DT), EII(DT),
DefaultBlockScanLimit(DefaultBlockScanLimit) {}
/// Handle invalidation in the new PM.
diff --git a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
index 49a31a52cf0e850..1c1a0873ac520f9 100644
--- a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -268,7 +268,7 @@ MemDepResult MemoryDependenceResults::getPointerDependencyFrom(
MemDepResult MemoryDependenceResults::getPointerDependencyFrom(
const MemoryLocation &MemLoc, bool isLoad, BasicBlock::iterator ScanIt,
BasicBlock *BB, Instruction *QueryInst, unsigned *Limit) {
- BatchAAResults BatchAA(AA);
+ BatchAAResults BatchAA(AA, &EII);
return getPointerDependencyFrom(MemLoc, isLoad, ScanIt, BB, QueryInst, Limit,
BatchAA);
}
@@ -645,11 +645,7 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
continue;
// See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
- ModRefInfo MR = BatchAA.getModRefInfo(Inst, MemLoc);
- // If necessary, perform additional analysis.
- if (isModAndRefSet(MR))
- MR = BatchAA.callCapturesBefore(Inst, MemLoc, &DT);
- switch (MR) {
+ switch (BatchAA.getModRefInfo(Inst, MemLoc)) {
case ModRefInfo::NoModRef:
// If the call has no effect on the queried pointer, just ignore it.
continue;
@@ -1227,7 +1223,7 @@ bool MemoryDependenceResults::getNonLocalPointerDepFromBB(
bool GotWorklistLimit = false;
LLVM_DEBUG(AssertSorted(*Cache));
- BatchAAResults BatchAA(AA);
+ BatchAAResults BatchAA(AA, &EII);
while (!Worklist.empty()) {
BasicBlock *BB = Worklist.pop_back_val();
@@ -1539,6 +1535,8 @@ void MemoryDependenceResults::invalidateCachedPredecessors() {
}
void MemoryDependenceResults::removeInstruction(Instruction *RemInst) {
+ EII.removeInstruction(RemInst);
+
// Walk through the Non-local dependencies, removing this one as the value
// for any cached queries.
NonLocalDepMapType::iterator NLDI = NonLocalDepsMap.find(RemInst);
diff --git a/llvm/test/CodeGen/BPF/CORE/no-narrow-load.ll b/llvm/test/CodeGen/BPF/CORE/no-narrow-load.ll
index b154b1d29fa24bf..dbfc4d2f99fc56d 100644
--- a/llvm/test/CodeGen/BPF/CORE/no-narrow-load.ll
+++ b/llvm/test/CodeGen/BPF/CORE/no-narrow-load.ll
@@ -65,10 +65,10 @@ lor.end: ; preds = %lor.end.critedge, %
ret void, !dbg !53
}
-; CHECK: r[[LOAD1:[0-9]+]] = *(u32 *)(r{{[0-9]+}} + 4)
-; CHECK: r[[LOAD1]] &= 65536
-; CHECK: r[[LOAD2:[0-9]+]] = *(u32 *)(r{{[0-9]+}} + 4)
-; CHECK: r[[LOAD2]] &= 32768
+; CHECK: r[[LOAD:[0-9]+]] = *(u32 *)(r{{[0-9]+}} + 4)
+; CHECK: r[[COPY:[0-9]+]] = r[[LOAD]]
+; CHECK: r[[COPY]] &= 65536
+; CHECK: r[[LOAD]] &= 32768
; Function Attrs: nounwind readnone speculatable willreturn
declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
diff --git a/llvm/test/Transforms/GVN/captured-before.ll b/llvm/test/Transforms/GVN/captured-before.ll
index 4e025b3f772e103..6d012edea34610f 100644
--- a/llvm/test/Transforms/GVN/captured-before.ll
+++ b/llvm/test/Transforms/GVN/captured-before.ll
@@ -46,9 +46,8 @@ define i32 @test_store_before_capture(ptr %p) {
; CHECK-NEXT: store i32 123, ptr [[A]], align 4
; CHECK-NEXT: [[P2:%.*]] = load ptr, ptr [[P]], align 8
; CHECK-NEXT: store i32 42, ptr [[P2]], align 4
-; CHECK-NEXT: [[V:%.*]] = load i32, ptr [[A]], align 4
; CHECK-NEXT: call void @capture(ptr [[A]])
-; CHECK-NEXT: ret i32 [[V]]
+; CHECK-NEXT: ret i32 123
;
%a = alloca i32
store i32 123, ptr %a
``````````
</details>
https://github.com/llvm/llvm-project/pull/69727
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