[llvm] r219899 - TRE: make TRE a bit more aggressive
Nick Lewycky
nlewycky at google.com
Fri Oct 17 12:55:19 PDT 2014
On 17 October 2014 12:14, Rafael Espíndola <rafael.espindola at gmail.com>
wrote:
> Is this actually safe?
>
I haven't been able to find a case where byval causes the allocation to be
on the callee stack, only on the caller stack.
The caller will deallocate the stack and then pass a pointer to that
> area to the callee...
>
> On 15 October 2014 23:27, Saleem Abdulrasool <compnerd at compnerd.org>
> wrote:
> > Author: compnerd
> > Date: Wed Oct 15 22:27:30 2014
> > New Revision: 219899
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=219899&view=rev
> > Log:
> > TRE: make TRE a bit more aggressive
> >
> > Make tail recursion elimination a bit more aggressive. This allows us
> to get
> > tail recursion on functions that are just branches to a different
> function. The
> > fact that the function takes a byval argument does not restrict it from
> being
> > optimised into just a tail call.
> >
> > Added:
> > llvm/trunk/test/Transforms/TailCallElim/byval.ll
> > Modified:
> > llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp
> > llvm/trunk/test/Transforms/Inline/byval-tail-call.ll
> > llvm/trunk/test/Transforms/TailCallElim/basic.ll
> >
> > Modified: llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp?rev=219899&r1=219898&r2=219899&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp
> (original)
> > +++ llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp Wed
> Oct 15 22:27:30 2014
> > @@ -249,12 +249,7 @@ bool TailCallElim::markTails(Function &F
> > return false;
> > AllCallsAreTailCalls = true;
> >
> > - // The local stack holds all alloca instructions and all byval
> arguments.
> > AllocaDerivedValueTracker Tracker;
> > - for (Argument &Arg : F.args()) {
> > - if (Arg.hasByValAttr())
> > - Tracker.walk(&Arg);
> > - }
> > for (auto &BB : F) {
> > for (auto &I : BB)
> > if (AllocaInst *AI = dyn_cast<AllocaInst>(&I))
> > @@ -310,9 +305,8 @@ bool TailCallElim::markTails(Function &F
> > for (auto &Arg : CI->arg_operands()) {
> > if (isa<Constant>(Arg.getUser()))
> > continue;
> > - if (Argument *A = dyn_cast<Argument>(Arg.getUser()))
> > - if (!A->hasByValAttr())
> > - continue;
> > + if (isa<Argument>(Arg.getUser()))
> > + continue;
> > SafeToTail = false;
> > break;
> > }
> >
> > Modified: llvm/trunk/test/Transforms/Inline/byval-tail-call.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Inline/byval-tail-call.ll?rev=219899&r1=219898&r2=219899&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/test/Transforms/Inline/byval-tail-call.ll (original)
> > +++ llvm/trunk/test/Transforms/Inline/byval-tail-call.ll Wed Oct 15
> 22:27:30 2014
> > @@ -27,10 +27,11 @@ define internal void @qux(i32* byval %x)
> > tail call void @ext(i32* null)
> > ret void
> > }
> > +
> > define void @frob(i32* %x) {
> > ; CHECK-LABEL: define void @frob(
> > ; CHECK: alloca i32
> > -; CHECK: {{^ *}}call void @ext(
> > +; CHECK: {{^ *}}tail call void @ext(
> > ; CHECK: tail call void @ext(i32* null)
> > ; CHECK: ret void
> > tail call void @qux(i32* byval %x)
> >
> > Modified: llvm/trunk/test/Transforms/TailCallElim/basic.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/TailCallElim/basic.ll?rev=219899&r1=219898&r2=219899&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/test/Transforms/TailCallElim/basic.ll (original)
> > +++ llvm/trunk/test/Transforms/TailCallElim/basic.ll Wed Oct 15 22:27:30
> 2014
> > @@ -147,7 +147,7 @@ cond_false:
> > ; Don't tail call if a byval arg is captured.
> > define void @test9(i32* byval %a) {
> > ; CHECK-LABEL: define void @test9(
> > -; CHECK: {{^ *}}call void @use(
> > +; CHECK: {{^ *}}tail call void @use(
> > call void @use(i32* %a)
> > ret void
> > }
> >
> > Added: llvm/trunk/test/Transforms/TailCallElim/byval.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/TailCallElim/byval.ll?rev=219899&view=auto
> >
> ==============================================================================
> > --- llvm/trunk/test/Transforms/TailCallElim/byval.ll (added)
> > +++ llvm/trunk/test/Transforms/TailCallElim/byval.ll Wed Oct 15 22:27:30
> 2014
> > @@ -0,0 +1,34 @@
> > +; RUN: opt -mtriple i386 -Os -S %s -o - | FileCheck %s
> > +; RUN: opt -mtriple x86_64 -Os -S %s -o - | FileCheck %s
> > +; RUN: opt -mtriple armv7 -Os -S %s -o - | FileCheck %s
> > +
> > +%struct.D16 = type { [16 x double] }
> > +
> > +declare void @_Z2OpP3D16PKS_S2_(%struct.D16*, %struct.D16*,
> %struct.D16*)
> > +
> > +define void @_Z7TestRefRK3D16S1_(%struct.D16* noalias sret %agg.result,
> %struct.D16* %RHS, %struct.D16* %LHS) {
> > + %1 = alloca %struct.D16*, align 8
> > + %2 = alloca %struct.D16*, align 8
> > + store %struct.D16* %RHS, %struct.D16** %1, align 8
> > + store %struct.D16* %LHS, %struct.D16** %2, align 8
> > + %3 = load %struct.D16** %1, align 8
> > + %4 = load %struct.D16** %2, align 8
> > + call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result, %struct.D16*
> %3, %struct.D16* %4)
> > + ret void
> > +}
> > +
> > +; CHECK: define void @_Z7TestRefRK3D16S1_({{.*}}) {
> > +; CHECK: tail call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result,
> %struct.D16* %RHS, %struct.D16* %LHS)
> > +; CHECK: ret void
> > +; CHECK: }
> > +
> > +define void @_Z7TestVal3D16S_(%struct.D16* noalias sret %agg.result,
> %struct.D16* byval align 8 %RHS, %struct.D16* byval align 8 %LHS) {
> > + call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result, %struct.D16*
> %RHS, %struct.D16* %LHS)
> > + ret void
> > +}
> > +
> > +; CHECK: define void @_Z7TestVal3D16S_({{.*}}) {
> > +; CHECK: tail call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result,
> %struct.D16* %RHS, %struct.D16* %LHS)
> > +; CHECK: ret void
> > +; CHECK: }
> > +
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
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