[llvm-commits] [llvm] r166407 - in /llvm/trunk: lib/Transforms/Scalar/TailRecursionElimination.cpp test/Transforms/TailCallElim/nocapture.ll
Argyrios Kyrtzidis
kyrtzidis at apple.com
Mon Oct 22 11:22:14 PDT 2012
Hi Nick,
I reverted this in r166424 because it crashes some (highly recursive) clang analyzer tests.
In order to reproduce configure as:
configure --build=x86_64-apple-darwin11 --host=x86_64-apple-darwin11 --enable-optimized --disable-assertions --disable-bindings --with-llvmcc=clang --without-llvmgcc --without-llvmgxx --enable-keep-symbols CC=/path/to/built/clang CXX=/path/to/built/clang++
the tests that crash:
Clang :: Analysis/dead-stores.cpp
Clang :: Analysis/inlining/stl.cpp
Clang :: Analysis/templates.cpp
-Argyrios
On Oct 21, 2012, at 8:03 PM, Nick Lewycky <nicholas at mxc.ca> wrote:
> Author: nicholas
> Date: Sun Oct 21 22:03:52 2012
> New Revision: 166407
>
> URL: http://llvm.org/viewvc/llvm-project?rev=166407&view=rev
> Log:
> Reapply r166405, teaching tailcallelim to be smarter about nocapture, with a
> very small but very important bugfix:
> bool shouldExplore(Use *U) {
> Value *V = U->get();
> if (isa<CallInst>(V) || isa<InvokeInst>(V))
> [...]
> should have read:
> bool shouldExplore(Use *U) {
> Value *V = U->getUser();
> if (isa<CallInst>(V) || isa<InvokeInst>(V))
> Fixes PR14143!
>
>
> Modified:
> llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp
> llvm/trunk/test/Transforms/TailCallElim/nocapture.ll
>
> Modified: llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp?rev=166407&r1=166406&r2=166407&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp Sun Oct 21 22:03:52 2012
> @@ -69,6 +69,7 @@
> #include "llvm/Support/CFG.h"
> #include "llvm/Support/Debug.h"
> #include "llvm/Support/raw_ostream.h"
> +#include "llvm/Support/ValueHandle.h"
> #include "llvm/ADT/Statistic.h"
> #include "llvm/ADT/STLExtras.h"
> using namespace llvm;
> @@ -117,35 +118,46 @@
> return new TailCallElim();
> }
>
> -/// AllocaMightEscapeToCalls - Return true if this alloca may be accessed by
> -/// callees of this function. We only do very simple analysis right now, this
> -/// could be expanded in the future to use mod/ref information for particular
> -/// call sites if desired.
> -static bool AllocaMightEscapeToCalls(AllocaInst *AI) {
> - // FIXME: do simple 'address taken' analysis.
> - return true;
> -}
> +/// CanTRE - Scan the specified basic block for alloca instructions.
> +/// If it contains any that are variable-sized or not in the entry block,
> +/// returns false.
> +static bool CanTRE(AllocaInst *AI) {
> + // Because of PR962, we don't TRE allocas outside the entry block.
>
> -/// CheckForEscapingAllocas - Scan the specified basic block for alloca
> -/// instructions. If it contains any that might be accessed by calls, return
> -/// true.
> -static bool CheckForEscapingAllocas(BasicBlock *BB,
> - bool &CannotTCETailMarkedCall) {
> - bool RetVal = false;
> - for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
> - if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
> - RetVal |= AllocaMightEscapeToCalls(AI);
> -
> - // If this alloca is in the body of the function, or if it is a variable
> - // sized allocation, we cannot tail call eliminate calls marked 'tail'
> - // with this mechanism.
> - if (BB != &BB->getParent()->getEntryBlock() ||
> - !isa<ConstantInt>(AI->getArraySize()))
> - CannotTCETailMarkedCall = true;
> - }
> - return RetVal;
> + // If this alloca is in the body of the function, or if it is a variable
> + // sized allocation, we cannot tail call eliminate calls marked 'tail'
> + // with this mechanism.
> + BasicBlock *BB = AI->getParent();
> + return BB == &BB->getParent()->getEntryBlock() &&
> + isa<ConstantInt>(AI->getArraySize());
> }
>
> +struct AllocaCaptureTracker : public CaptureTracker {
> + AllocaCaptureTracker() : Captured(false) {}
> +
> + void tooManyUses() { Captured = true; }
> +
> + bool shouldExplore(Use *U) {
> + Value *V = U->getUser();
> + if (isa<CallInst>(V) || isa<InvokeInst>(V))
> + UsesAlloca.push_back(V);
> +
> + return true;
> + }
> +
> + bool captured(Use *U) {
> + if (isa<ReturnInst>(U->getUser()))
> + return false;
> +
> + Captured = true;
> + return true;
> + }
> +
> + SmallVector<WeakVH, 64> UsesAlloca;
> +
> + bool Captured;
> +};
> +
> bool TailCallElim::runOnFunction(Function &F) {
> // If this function is a varargs function, we won't be able to PHI the args
> // right, so don't even try to convert it...
> @@ -157,38 +169,34 @@
> bool MadeChange = false;
> bool FunctionContainsEscapingAllocas = false;
>
> - // CannotTCETailMarkedCall - If true, we cannot perform TCE on tail calls
> + // CanTRETailMarkedCall - If false, we cannot perform TRE on tail calls
> // marked with the 'tail' attribute, because doing so would cause the stack
> - // size to increase (real TCE would deallocate variable sized allocas, TCE
> + // size to increase (real TRE would deallocate variable sized allocas, TRE
> // doesn't).
> - bool CannotTCETailMarkedCall = false;
> -
> - // Loop over the function, looking for any returning blocks, and keeping track
> - // of whether this function has any non-trivially used allocas.
> - for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
> - if (FunctionContainsEscapingAllocas && CannotTCETailMarkedCall)
> - break;
> + bool CanTRETailMarkedCall = true;
>
> - FunctionContainsEscapingAllocas |=
> - CheckForEscapingAllocas(BB, CannotTCETailMarkedCall);
> + // Find calls that can be marked tail.
> + AllocaCaptureTracker ACT;
> + for (Function::iterator BB = F.begin(), EE = F.end(); BB != EE; ++BB) {
> + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
> + if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
> + CanTRETailMarkedCall &= CanTRE(AI);
> + PointerMayBeCaptured(AI, &ACT);
> + if (ACT.Captured)
> + return false;
> + }
> + }
> }
>
> - /// FIXME: The code generator produces really bad code when an 'escaping
> - /// alloca' is changed from being a static alloca to being a dynamic alloca.
> - /// Until this is resolved, disable this transformation if that would ever
> - /// happen. This bug is PR962.
> - if (FunctionContainsEscapingAllocas)
> - return false;
> -
> - // Second pass, change any tail calls to loops.
> + // Second pass, change any tail recursive calls to loops.
> for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
> if (ReturnInst *Ret = dyn_cast<ReturnInst>(BB->getTerminator())) {
> bool Change = ProcessReturningBlock(Ret, OldEntry, TailCallsAreMarkedTail,
> - ArgumentPHIs,CannotTCETailMarkedCall);
> + ArgumentPHIs, !CanTRETailMarkedCall);
> if (!Change && BB->getFirstNonPHIOrDbg() == Ret)
> Change = FoldReturnAndProcessPred(BB, Ret, OldEntry,
> TailCallsAreMarkedTail, ArgumentPHIs,
> - CannotTCETailMarkedCall);
> + !CanTRETailMarkedCall);
> MadeChange |= Change;
> }
> }
> @@ -210,21 +218,24 @@
> }
> }
>
> - // Finally, if this function contains no non-escaping allocas, or calls
> - // setjmp, mark all calls in the function as eligible for tail calls
> - //(there is no stack memory for them to access).
> + // Finally, if this function contains no non-escaping allocas and doesn't
> + // call setjmp, mark all calls in the function as eligible for tail calls
> + // (there is no stack memory for them to access).
> + std::sort(ACT.UsesAlloca.begin(), ACT.UsesAlloca.end());
> +
> if (!FunctionContainsEscapingAllocas && !F.callsFunctionThatReturnsTwice())
> for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
> for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
> - if (CallInst *CI = dyn_cast<CallInst>(I)) {
> - CI->setTailCall();
> - MadeChange = true;
> - }
> + if (CallInst *CI = dyn_cast<CallInst>(I))
> + if (!std::binary_search(ACT.UsesAlloca.begin(), ACT.UsesAlloca.end(),
> + CI)) {
> + CI->setTailCall();
> + MadeChange = true;
> + }
>
> return MadeChange;
> }
>
> -
> /// CanMoveAboveCall - Return true if it is safe to move the specified
> /// instruction from after the call to before the call, assuming that all
> /// instructions between the call and this instruction are movable.
>
> Modified: llvm/trunk/test/Transforms/TailCallElim/nocapture.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/TailCallElim/nocapture.ll?rev=166407&r1=166406&r2=166407&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/TailCallElim/nocapture.ll (original)
> +++ llvm/trunk/test/Transforms/TailCallElim/nocapture.ll Sun Oct 21 22:03:52 2012
> @@ -1,9 +1,9 @@
> ; RUN: opt %s -tailcallelim -S | FileCheck %s
> -; XFAIL: *
>
> declare void @use(i8* nocapture, i8* nocapture)
> +declare void @boring()
>
> -define i8* @foo(i8* nocapture %A, i1 %cond) {
> +define i8* @test1(i8* nocapture %A, i1 %cond) {
> ; CHECK: tailrecurse:
> ; CHECK: %A.tr = phi i8* [ %A, %0 ], [ %B, %cond_true ]
> ; CHECK: %cond.tr = phi i1 [ %cond, %0 ], [ false, %cond_true ]
> @@ -14,12 +14,27 @@
> cond_true:
> ; CHECK: cond_true:
> ; CHECK: br label %tailrecurse
> - call i8* @foo(i8* %B, i1 false)
> + call i8* @test1(i8* %B, i1 false)
> ret i8* null
> cond_false:
> ; CHECK: cond_false
> call void @use(i8* %A, i8* %B)
> -; CHECK: tail call void @use(i8* %A.tr, i8* %B)
> +; CHECK: call void @use(i8* %A.tr, i8* %B)
> + call void @boring()
> +; CHECK: tail call void @boring()
> ret i8* null
> ; CHECK: ret i8* null
> }
> +
> +; PR14143
> +define void @test2(i8* %a, i8* %b) {
> +; CHECK: @test2
> +; CHECK-NOT: tail call
> +; CHECK: ret void
> + %c = alloca [100 x i8], align 16
> + %tmp = bitcast [100 x i8]* %c to i8*
> + call void @llvm.memcpy.p0i8.p0i8.i64(i8* %b, i8* %tmp, i64 100, i32 1, i1 false)
> + ret void
> +}
> +
> +declare void @llvm.memcpy.p0i8.p0i8.i64(i8*, i8*, i64, i32, i1)
>
>
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