[llvm-commits] [llvm] r89398 - in /llvm/trunk: include/llvm/Analysis/CaptureTracking.h lib/Analysis/BasicAliasAnalysis.cpp lib/Analysis/CaptureTracking.cpp lib/Transforms/IPO/FunctionAttrs.cpp test/Transforms/GVN/nonescaping-malloc.ll
Nick Lewycky
nicholas at mxc.ca
Thu Nov 19 23:15:48 PST 2009
Dan Gohman wrote:
> Author: djg
> Date: Thu Nov 19 15:57:48 2009
> New Revision: 89398
>
> URL: http://llvm.org/viewvc/llvm-project?rev=89398&view=rev
> Log:
> Extend CaptureTracking to indicate when a value is never stored, even
> if it is not ultimately captured. Teach BasicAliasAnalysis that a
> local object address which does not escape and is never stored does
> not alias with a value resulting from a load.
>
> Added:
> llvm/trunk/test/Transforms/GVN/nonescaping-malloc.ll
> Modified:
> llvm/trunk/include/llvm/Analysis/CaptureTracking.h
> llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
> llvm/trunk/lib/Analysis/CaptureTracking.cpp
> llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp
>
> Modified: llvm/trunk/include/llvm/Analysis/CaptureTracking.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/CaptureTracking.h?rev=89398&r1=89397&r2=89398&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/Analysis/CaptureTracking.h (original)
> +++ llvm/trunk/include/llvm/Analysis/CaptureTracking.h Thu Nov 19 15:57:48 2009
> @@ -21,8 +21,12 @@
> /// by the enclosing function (which is required to exist). This routine can
> /// be expensive, so consider caching the results. The boolean ReturnCaptures
> /// specifies whether returning the value (or part of it) from the function
> + /// counts as capturing it or not. The boolean StoreCaptures specified whether
> + /// storing the value (or part of it) into memory anywhere automatically
> /// counts as capturing it or not.
> - bool PointerMayBeCaptured(const Value *V, bool ReturnCaptures);
> + bool PointerMayBeCaptured(const Value *V,
> + bool ReturnCaptures,
> + bool StoreCaptures);
I completely do not understand this. The fact that store implies capture
has always been a missed opportunity; if it stores to something that
never escapes, and the loads of it never escape, then it's not captured.
(Note that you need to track 'pointer depth' as %p is stored into %q is
stored into %r, etc.)
Duncan (IIRC) actually implemented this behaviour early on and we
removed it because it was likely to be slow and didn't seem to provide
any performance benefit at the time.
In any event, either I'm misunderstanding what you're doing here, or it
doesn't belong in the API.
Nick
> } // end namespace llvm
>
>
> Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=89398&r1=89397&r2=89398&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
> +++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Thu Nov 19 15:57:48 2009
> @@ -79,7 +79,12 @@
> static bool isNonEscapingLocalObject(const Value *V) {
> // If this is a local allocation, check to see if it escapes.
> if (isa<AllocaInst>(V) || isNoAliasCall(V))
> - return !PointerMayBeCaptured(V, false);
> + // Set StoreCaptures to True so that we can assume in our callers that the
> + // pointer is not the result of a load instruction. Currently
> + // PointerMayBeCaptured doesn't have any special analysis for the
> + // StoreCaptures=false case; if it did, our callers could be refined to be
> + // more precise.
> + return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
>
> // If this is an argument that corresponds to a byval or noalias argument,
> // then it has not escaped before entering the function. Check if it escapes
> @@ -89,7 +94,7 @@
> // Don't bother analyzing arguments already known not to escape.
> if (A->hasNoCaptureAttr())
> return true;
> - return !PointerMayBeCaptured(V, false);
> + return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
> }
> return false;
> }
> @@ -683,15 +688,19 @@
> (V2Size != ~0U&& isObjectSmallerThan(O1, V2Size, *TD)))
> return NoAlias;
>
> - // If one pointer is the result of a call/invoke and the other is a
> + // If one pointer is the result of a call/invoke or load and the other is a
> // non-escaping local object, then we know the object couldn't escape to a
> - // point where the call could return it.
> - if ((isa<CallInst>(O1) || isa<InvokeInst>(O1))&&
> - isNonEscapingLocalObject(O2)&& O1 != O2)
> - return NoAlias;
> - if ((isa<CallInst>(O2) || isa<InvokeInst>(O2))&&
> - isNonEscapingLocalObject(O1)&& O1 != O2)
> - return NoAlias;
> + // point where the call could return it. The load case works because
> + // isNonEscapingLocalObject considers all stores to be escapes (it
> + // passes true for the StoreCaptures argument to PointerMayBeCaptured).
> + if (O1 != O2) {
> + if ((isa<CallInst>(O1) || isa<InvokeInst>(O1) || isa<LoadInst>(O1))&&
> + isNonEscapingLocalObject(O2))
> + return NoAlias;
> + if ((isa<CallInst>(O2) || isa<InvokeInst>(O2) || isa<LoadInst>(O2))&&
> + isNonEscapingLocalObject(O1))
> + return NoAlias;
> + }
>
> if (!isa<GEPOperator>(V1)&& isa<GEPOperator>(V2)) {
> std::swap(V1, V2);
>
> Modified: llvm/trunk/lib/Analysis/CaptureTracking.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CaptureTracking.cpp?rev=89398&r1=89397&r2=89398&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Analysis/CaptureTracking.cpp (original)
> +++ llvm/trunk/lib/Analysis/CaptureTracking.cpp Thu Nov 19 15:57:48 2009
> @@ -28,8 +28,11 @@
> /// by the enclosing function (which is required to exist). This routine can
> /// be expensive, so consider caching the results. The boolean ReturnCaptures
> /// specifies whether returning the value (or part of it) from the function
> +/// counts as capturing it or not. The boolean StoreCaptures specified whether
> +/// storing the value (or part of it) into memory anywhere automatically
> /// counts as capturing it or not.
> -bool llvm::PointerMayBeCaptured(const Value *V, bool ReturnCaptures) {
> +bool llvm::PointerMayBeCaptured(const Value *V,
> + bool ReturnCaptures, bool StoreCaptures) {
> assert(isa<PointerType>(V->getType())&& "Capture is for pointers only!");
> SmallVector<Use*, 16> Worklist;
> SmallSet<Use*, 16> Visited;
> @@ -82,7 +85,11 @@
> break;
> case Instruction::Store:
> if (V == I->getOperand(0))
> - // Stored the pointer - it may be captured.
> + // Stored the pointer - conservatively assume it may be captured.
> + // TODO: If StoreCaptures is not true, we could do Fancy analysis
> + // to determine whether this store is not actually an escape point.
> + // In that case, BasicAliasAnalysis should be updated as well to
> + // take advantage of this.
> return true;
> // Storing to the pointee does not cause the pointer to be captured.
> break;
>
> Modified: llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp?rev=89398&r1=89397&r2=89398&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp (original)
> +++ llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp Thu Nov 19 15:57:48 2009
> @@ -212,7 +212,7 @@
>
> for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end(); A!=E; ++A)
> if (isa<PointerType>(A->getType())&& !A->hasNoCaptureAttr()&&
> - !PointerMayBeCaptured(A, true)) {
> + !PointerMayBeCaptured(A, true, /*StoreCaptures=*/false)) {
> A->addAttr(Attribute::NoCapture);
> ++NumNoCapture;
> Changed = true;
> @@ -280,7 +280,7 @@
> return false; // Did not come from an allocation.
> }
>
> - if (PointerMayBeCaptured(RetVal, false))
> + if (PointerMayBeCaptured(RetVal, false, /*StoreCaptures=*/false))
> return false;
> }
>
>
> Added: llvm/trunk/test/Transforms/GVN/nonescaping-malloc.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVN/nonescaping-malloc.ll?rev=89398&view=auto
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/GVN/nonescaping-malloc.ll (added)
> +++ llvm/trunk/test/Transforms/GVN/nonescaping-malloc.ll Thu Nov 19 15:57:48 2009
> @@ -0,0 +1,108 @@
> +; RUN: opt< %s -gvn -stats |& grep {Number of loads deleted}
> +; rdar://7363102
> +
> +; GVN should be able to eliminate load %tmp22.i, because it is redundant with
> +; load %tmp8.i. This requires being able to prove that %tmp7.i doesn't
> +; alias the malloc'd value %tmp.i20.i.i, which it can do since %tmp7.i
> +; is derived from %tmp5.i which is computed from a load, and %tmp.i20.i.i
> +; is never stored and does not escape.
> +
> +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"
> +target triple = "x86_64-apple-darwin10.0"
> +
> +%"struct.llvm::MallocAllocator" = type<{ i8 }>
> +%"struct.llvm::StringMap<void*,llvm::MallocAllocator>" = type { %"struct.llvm::StringMapImpl", %"struct.llvm::MallocAllocator" }
> +%"struct.llvm::StringMapEntry<void*>" = type { %"struct.llvm::StringMapEntryBase", i8* }
> +%"struct.llvm::StringMapEntryBase" = type { i32 }
> +%"struct.llvm::StringMapImpl" = type { %"struct.llvm::StringMapImpl::ItemBucket"*, i32, i32, i32, i32 }
> +%"struct.llvm::StringMapImpl::ItemBucket" = type { i32, %"struct.llvm::StringMapEntryBase"* }
> +%"struct.llvm::StringRef" = type { i8*, i64 }
> +
> +define %"struct.llvm::StringMapEntry<void*>"* @_Z3fooRN4llvm9StringMapIPvNS_15MallocAllocatorEEEPKc(%"struct.llvm::StringMap<void*,llvm::MallocAllocator>"* %X, i8* %P) ssp {
> +entry:
> + %tmp = alloca %"struct.llvm::StringRef", align 8 ;<%"struct.llvm::StringRef"*> [#uses=3]
> + %tmp.i = getelementptr inbounds %"struct.llvm::StringRef"* %tmp, i64 0, i32 0 ;<i8**> [#uses=1]
> + store i8* %P, i8** %tmp.i, align 8
> + %tmp1.i = call i64 @strlen(i8* %P) nounwind readonly ;<i64> [#uses=1]
> + %tmp2.i = getelementptr inbounds %"struct.llvm::StringRef"* %tmp, i64 0, i32 1 ;<i64*> [#uses=1]
> + store i64 %tmp1.i, i64* %tmp2.i, align 8
> + %tmp1 = call %"struct.llvm::StringMapEntry<void*>"* @_ZN4llvm9StringMapIPvNS_15MallocAllocatorEE16GetOrCreateValueERKNS_9StringRefE(%"struct.llvm::StringMap<void*,llvm::MallocAllocator>"* %X, %"struct.llvm::StringRef"* %tmp) ssp ;<%"struct.llvm::StringMapEntry<void*>"*> [#uses=1]
> + ret %"struct.llvm::StringMapEntry<void*>"* %tmp1
> +}
> +
> +declare i64 @strlen(i8* nocapture) nounwind readonly
> +
> +declare noalias i8* @malloc(i64) nounwind
> +
> +declare void @llvm.memcpy.i64(i8* nocapture, i8* nocapture, i64, i32) nounwind
> +
> +declare i32 @_ZN4llvm13StringMapImpl15LookupBucketForENS_9StringRefE(%"struct.llvm::StringMapImpl"*, i64, i64)
> +
> +define linkonce_odr %"struct.llvm::StringMapEntry<void*>"* @_ZN4llvm9StringMapIPvNS_15MallocAllocatorEE16GetOrCreateValueERKNS_9StringRefE(%"struct.llvm::StringMap<void*,llvm::MallocAllocator>"* %this, %"struct.llvm::StringRef"* nocapture %Key) ssp align 2 {
> +entry:
> + %elt = bitcast %"struct.llvm::StringRef"* %Key to i64* ;<i64*> [#uses=1]
> + %val = load i64* %elt ;<i64> [#uses=3]
> + %tmp = getelementptr inbounds %"struct.llvm::StringRef"* %Key, i64 0, i32 1 ;<i64*> [#uses=1]
> + %val2 = load i64* %tmp ;<i64> [#uses=2]
> + %tmp2.i = getelementptr inbounds %"struct.llvm::StringMap<void*,llvm::MallocAllocator>"* %this, i64 0, i32 0 ;<%"struct.llvm::StringMapImpl"*> [#uses=1]
> + %tmp3.i = tail call i32 @_ZN4llvm13StringMapImpl15LookupBucketForENS_9StringRefE(%"struct.llvm::StringMapImpl"* %tmp2.i, i64 %val, i64 %val2) ;<i32> [#uses=1]
> + %tmp4.i = getelementptr inbounds %"struct.llvm::StringMap<void*,llvm::MallocAllocator>"* %this, i64 0, i32 0, i32 0 ;<%"struct.llvm::StringMapImpl::ItemBucket"**> [#uses=1]
> + %tmp5.i = load %"struct.llvm::StringMapImpl::ItemBucket"** %tmp4.i, align 8 ;<%"struct.llvm::StringMapImpl::ItemBucket"*> [#uses=1]
> + %tmp6.i = zext i32 %tmp3.i to i64 ;<i64> [#uses=1]
> + %tmp7.i = getelementptr inbounds %"struct.llvm::StringMapImpl::ItemBucket"* %tmp5.i, i64 %tmp6.i, i32 1 ;<%"struct.llvm::StringMapEntryBase"**> [#uses=2]
> + %tmp8.i = load %"struct.llvm::StringMapEntryBase"** %tmp7.i, align 8 ;<%"struct.llvm::StringMapEntryBase"*> [#uses=3]
> + %tmp9.i = icmp eq %"struct.llvm::StringMapEntryBase"* %tmp8.i, null ;<i1> [#uses=1]
> + %tmp13.i = icmp eq %"struct.llvm::StringMapEntryBase"* %tmp8.i, inttoptr (i64 -1 to %"struct.llvm::StringMapEntryBase"*) ;<i1> [#uses=1]
> + %or.cond.i = or i1 %tmp9.i, %tmp13.i ;<i1> [#uses=1]
> + br i1 %or.cond.i, label %bb4.i, label %bb6.i
> +
> +bb4.i: ; preds = %entry
> + %tmp41.i = inttoptr i64 %val to i8* ;<i8*> [#uses=2]
> + %tmp4.i35.i = getelementptr inbounds i8* %tmp41.i, i64 %val2 ;<i8*> [#uses=1]
> + %tmp.i.i = ptrtoint i8* %tmp4.i35.i to i64 ;<i64> [#uses=1]
> + %tmp1.i.i = trunc i64 %tmp.i.i to i32 ;<i32> [#uses=1]
> + %tmp3.i.i = trunc i64 %val to i32 ;<i32> [#uses=1]
> + %tmp4.i.i = sub i32 %tmp1.i.i, %tmp3.i.i ;<i32> [#uses=3]
> + %tmp5.i.i = add i32 %tmp4.i.i, 17 ;<i32> [#uses=1]
> + %tmp8.i.i = zext i32 %tmp5.i.i to i64 ;<i64> [#uses=1]
> + %tmp.i20.i.i = tail call noalias i8* @malloc(i64 %tmp8.i.i) nounwind ;<i8*> [#uses=7]
> + %tmp10.i.i = bitcast i8* %tmp.i20.i.i to %"struct.llvm::StringMapEntry<void*>"* ;<%"struct.llvm::StringMapEntry<void*>"*> [#uses=2]
> + %tmp12.i.i = icmp eq i8* %tmp.i20.i.i, null ;<i1> [#uses=1]
> + br i1 %tmp12.i.i, label %_ZN4llvm14StringMapEntryIPvE6CreateINS_15MallocAllocatorES1_EEPS2_PKcS7_RT_T0_.exit.i, label %bb.i.i
> +
> +bb.i.i: ; preds = %bb4.i
> + %tmp.i.i.i.i = bitcast i8* %tmp.i20.i.i to i32* ;<i32*> [#uses=1]
> + store i32 %tmp4.i.i, i32* %tmp.i.i.i.i, align 4
> + %tmp1.i19.i.i = getelementptr inbounds i8* %tmp.i20.i.i, i64 8 ;<i8*> [#uses=1]
> + %0 = bitcast i8* %tmp1.i19.i.i to i8** ;<i8**> [#uses=1]
> + store i8* null, i8** %0, align 8
> + br label %_ZN4llvm14StringMapEntryIPvE6CreateINS_15MallocAllocatorES1_EEPS2_PKcS7_RT_T0_.exit.i
> +
> +_ZN4llvm14StringMapEntryIPvE6CreateINS_15MallocAllocatorES1_EEPS2_PKcS7_RT_T0_.exit.i: ; preds = %bb4.i, %bb.i.i
> + %tmp.i18.i.i = getelementptr inbounds i8* %tmp.i20.i.i, i64 16 ;<i8*> [#uses=1]
> + %tmp15.i.i = zext i32 %tmp4.i.i to i64 ;<i64> [#uses=2]
> + tail call void @llvm.memcpy.i64(i8* %tmp.i18.i.i, i8* %tmp41.i, i64 %tmp15.i.i, i32 1) nounwind
> + %tmp.i18.sum.i.i = add i64 %tmp15.i.i, 16 ;<i64> [#uses=1]
> + %tmp17.i.i = getelementptr inbounds i8* %tmp.i20.i.i, i64 %tmp.i18.sum.i.i ;<i8*> [#uses=1]
> + store i8 0, i8* %tmp17.i.i, align 1
> + %tmp.i.i.i = getelementptr inbounds i8* %tmp.i20.i.i, i64 8 ;<i8*> [#uses=1]
> + %1 = bitcast i8* %tmp.i.i.i to i8** ;<i8**> [#uses=1]
> + store i8* null, i8** %1, align 8
> + %tmp22.i = load %"struct.llvm::StringMapEntryBase"** %tmp7.i, align 8 ;<%"struct.llvm::StringMapEntryBase"*> [#uses=1]
> + %tmp24.i = icmp eq %"struct.llvm::StringMapEntryBase"* %tmp22.i, inttoptr (i64 -1 to %"struct.llvm::StringMapEntryBase"*) ;<i1> [#uses=1]
> + br i1 %tmp24.i, label %bb9.i, label %_ZN4llvm9StringMapIPvNS_15MallocAllocatorEE16GetOrCreateValueIS1_EERNS_14StringMapEntryIS1_EENS_9StringRefET_.exit
> +
> +bb6.i: ; preds = %entry
> + %tmp16.i = bitcast %"struct.llvm::StringMapEntryBase"* %tmp8.i to %"struct.llvm::StringMapEntry<void*>"* ;<%"struct.llvm::StringMapEntry<void*>"*> [#uses=1]
> + ret %"struct.llvm::StringMapEntry<void*>"* %tmp16.i
> +
> +bb9.i: ; preds = %_ZN4llvm14StringMapEntryIPvE6CreateINS_15MallocAllocatorES1_EEPS2_PKcS7_RT_T0_.exit.i
> + %tmp25.i = getelementptr inbounds %"struct.llvm::StringMap<void*,llvm::MallocAllocator>"* %this, i64 0, i32 0, i32 3 ;<i32*> [#uses=2]
> + %tmp26.i = load i32* %tmp25.i, align 8 ;<i32> [#uses=1]
> + %tmp27.i = add i32 %tmp26.i, -1 ;<i32> [#uses=1]
> + store i32 %tmp27.i, i32* %tmp25.i, align 8
> + ret %"struct.llvm::StringMapEntry<void*>"* %tmp10.i.i
> +
> +_ZN4llvm9StringMapIPvNS_15MallocAllocatorEE16GetOrCreateValueIS1_EERNS_14StringMapEntryIS1_EENS_9StringRefET_.exit: ; preds = %_ZN4llvm14StringMapEntryIPvE6CreateINS_15MallocAllocatorES1_EEPS2_PKcS7_RT_T0_.exit.i
> + ret %"struct.llvm::StringMapEntry<void*>"* %tmp10.i.i
> +}
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
More information about the llvm-commits
mailing list