[llvm] r238487 - Disable x86 tail call optimizations that jump through GOT
Reid Kleckner
rnk at google.com
Thu May 28 14:28:06 PDT 2015
Woops, r238501.
On Thu, May 28, 2015 at 2:05 PM, Benjamin Kramer <benny.kra at gmail.com>
wrote:
>
> > On 28.05.2015, at 22:44, Reid Kleckner <reid at kleckner.net> wrote:
> >
> > Author: rnk
> > Date: Thu May 28 15:44:28 2015
> > New Revision: 238487
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=238487&view=rev
> > Log:
> > Disable x86 tail call optimizations that jump through GOT
> >
> > For x86 targets, do not do sibling call optimization when materializing
> > the callee's address would require a GOT relocation. We can still do
> > tail calls to internal functions, hidden functions, and protected
> > functions, because they do not require this kind of relocation. It is
> > still possible to get GOT relocations when the user explicitly asks for
> > it with musttail or -tailcallopt, both of which are supposed to
> > guarantee TCO.
> >
> > Based on a patch by Chih-hung Hsieh.
> >
> > Reviewers: srhines, timmurray, danalbert, enh, void, nadav, rnk
> >
> > Subscribers: joerg, davidxl, llvm-commits
> >
> > Differential Revision: http://reviews.llvm.org/D9799
> >
> > Added:
> > llvm/trunk/test/CodeGen/X86/tailcallpic3.ll
> > Modified:
> > llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
> > llvm/trunk/test/CodeGen/X86/pic.ll
> > llvm/trunk/test/CodeGen/X86/tail-call-got.ll
> > llvm/trunk/test/CodeGen/X86/tailcallpic1.ll
> >
> > Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=238487&r1=238486&r2=238487&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
> > +++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Thu May 28 15:44:28
> 2015
> > @@ -2780,6 +2780,24 @@ X86TargetLowering::LowerCall(TargetLower
> > if (MF.getTarget().Options.DisableTailCalls)
> > isTailCall = false;
> >
> > + if (Subtarget->isPICStyleGOT() &&
> > + !MF.getTarget().Options.GuaranteedTailCallOpt) {
> > + // If we are using a GOT, disable tail calls to external symbols
> with
> > + // default visibility. Tail calling such a symbol requires using a
> GOT
> > + // relocation, which forces early binding of the symbol. This
> breaks code
> > + // that require lazy function symbol resolution. Using musttail or
> > + // GuaranteedTailCallOpt will override this.
> > + GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee);
> > + if (!G || (!G->getGlobal()->hasLocalLinkage() &&
> > + G->getGlobal()->hasDefaultVisibility())) {
> > + isTailCall = false;
> > + if (G) {
> > + llvm::errs() << "disabling tail call for default visibility
> symbol\n";
> > + G->getGlobal()->dump();
>
> printf debugging leftovers?
>
> - Ben
>
> > + }
> > + }
> > + }
> > +
> > bool IsMustTail = CLI.CS && CLI.CS->isMustTailCall();
> > if (IsMustTail) {
> > // Force this to be a tail call. The verifier rules are enough to
> ensure
> > @@ -2964,8 +2982,8 @@ X86TargetLowering::LowerCall(TargetLower
> >
> > // Note: The actual moving to ECX is done further down.
> > GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee);
> > - if (G && !G->getGlobal()->hasHiddenVisibility() &&
> > - !G->getGlobal()->hasProtectedVisibility())
> > + if (G && !G->getGlobal()->hasLocalLinkage() &&
> > + G->getGlobal()->hasDefaultVisibility())
> > Callee = LowerGlobalAddress(Callee, DAG);
> > else if (isa<ExternalSymbolSDNode>(Callee))
> > Callee = LowerExternalSymbol(Callee, DAG);
> >
> > Modified: llvm/trunk/test/CodeGen/X86/pic.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pic.ll?rev=238487&r1=238486&r2=238487&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/test/CodeGen/X86/pic.ll (original)
> > +++ llvm/trunk/test/CodeGen/X86/pic.ll Thu May 28 15:44:28 2015
> > @@ -196,9 +196,11 @@ bb12:
> > ; LINUX-NEXT: .LJTI7_0:
> > ; LINUX: .long .LBB7_2 at GOTOFF
> > ; LINUX: .long .LBB7_8 at GOTOFF
> > -; LINUX: .long .LBB7_14 at GOTOFF
> > -; LINUX: .long .LBB7_9 at GOTOFF
> > -; LINUX: .long .LBB7_10 at GOTOFF
> > +; LINUX: .long .LBB7_4 at GOTOFF
> > +; LINUX: .long .LBB7_6 at GOTOFF
> > +; LINUX: .long .LBB7_5 at GOTOFF
> > +; LINUX: .long .LBB7_8 at GOTOFF
> > +; LINUX: .long .LBB7_7 at GOTOFF
> > }
> >
> > declare void @foo1(...)
> >
> > Modified: llvm/trunk/test/CodeGen/X86/tail-call-got.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/tail-call-got.ll?rev=238487&r1=238486&r2=238487&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/test/CodeGen/X86/tail-call-got.ll (original)
> > +++ llvm/trunk/test/CodeGen/X86/tail-call-got.ll Thu May 28 15:44:28 2015
> > @@ -1,12 +1,14 @@
> > ; RUN: llc < %s -relocation-model=pic -mattr=+sse2 | FileCheck %s
> >
> > +; We used to do tail calls through the GOT for these symbols, but it was
> > +; disabled due to PR15086.
> > +
> > target datalayout =
> "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
> > target triple = "i386-unknown-freebsd9.0"
> >
> > define double @test1(double %x) nounwind readnone {
> > ; CHECK-LABEL: test1:
> > -; CHECK: movl foo at GOT
> > -; CHECK-NEXT: jmpl
> > +; CHECK: calll foo at PLT
> > %1 = tail call double @foo(double %x) nounwind readnone
> > ret double %1
> > }
> > @@ -15,10 +17,18 @@ declare double @foo(double) readnone
> >
> > define double @test2(double %x) nounwind readnone {
> > ; CHECK-LABEL: test2:
> > -; CHECK: movl sin at GOT
> > -; CHECK-NEXT: jmpl
> > +; CHECK: calll sin at PLT
> > %1 = tail call double @sin(double %x) nounwind readnone
> > ret double %1
> > }
> >
> > declare double @sin(double) readnone
> > +
> > +define double @test3(double %x) nounwind readnone {
> > +; CHECK-LABEL: test3:
> > +; CHECK: calll sin2 at PLT
> > + %1 = tail call double @sin2(double %x) nounwind readnone
> > + ret double %1
> > +}
> > +
> > +declare double @sin2(double) readnone
> >
> > Modified: llvm/trunk/test/CodeGen/X86/tailcallpic1.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/tailcallpic1.ll?rev=238487&r1=238486&r2=238487&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/test/CodeGen/X86/tailcallpic1.ll (original)
> > +++ llvm/trunk/test/CodeGen/X86/tailcallpic1.ll Thu May 28 15:44:28 2015
> > @@ -1,5 +1,8 @@
> > ; RUN: llc < %s -tailcallopt -mtriple=i686-pc-linux-gnu
> -relocation-model=pic | FileCheck %s
> >
> > +; This test uses guaranteed TCO so these will be tail calls, despite
> the early
> > +; binding issues.
> > +
> > define protected fastcc i32 @tailcallee(i32 %a1, i32 %a2, i32 %a3, i32
> %a4) {
> > entry:
> > ret i32 %a3
> >
> > Added: llvm/trunk/test/CodeGen/X86/tailcallpic3.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/tailcallpic3.ll?rev=238487&view=auto
> >
> ==============================================================================
> > --- llvm/trunk/test/CodeGen/X86/tailcallpic3.ll (added)
> > +++ llvm/trunk/test/CodeGen/X86/tailcallpic3.ll Thu May 28 15:44:28 2015
> > @@ -0,0 +1,73 @@
> > +; RUN: llc < %s -mtriple=i686-pc-linux-gnu -relocation-model=pic |
> FileCheck %s
> > +
> > +; While many of these could be tail called, we don't do it because it
> forces
> > +; early binding.
> > +
> > +declare void @external()
> > +
> > +define hidden void @tailcallee_hidden() {
> > +entry:
> > + ret void
> > +}
> > +
> > +define void @tailcall_hidden() {
> > +entry:
> > + tail call void @tailcallee_hidden()
> > + ret void
> > +}
> > +; CHECK: tailcall_hidden:
> > +; CHECK: jmp tailcallee_hidden
> > +
> > +define internal void @tailcallee_internal() {
> > +entry:
> > + ret void
> > +}
> > +
> > +define void @tailcall_internal() {
> > +entry:
> > + tail call void @tailcallee_internal()
> > + ret void
> > +}
> > +; CHECK: tailcall_internal:
> > +; CHECK: jmp tailcallee_internal
> > +
> > +define default void @tailcallee_default() {
> > +entry:
> > + ret void
> > +}
> > +
> > +define void @tailcall_default() {
> > +entry:
> > + tail call void @tailcallee_default()
> > + ret void
> > +}
> > +; CHECK: tailcall_default:
> > +; CHECK: calll tailcallee_default at PLT
> > +
> > +define void @tailcallee_default_implicit() {
> > +entry:
> > + ret void
> > +}
> > +
> > +define void @tailcall_default_implicit() {
> > +entry:
> > + tail call void @tailcallee_default_implicit()
> > + ret void
> > +}
> > +; CHECK: tailcall_default_implicit:
> > +; CHECK: calll tailcallee_default_implicit at PLT
> > +
> > +define void @tailcall_external() {
> > + tail call void @external()
> > + ret void
> > +}
> > +; CHECK: tailcall_external:
> > +; CHECK: calll external at PLT
> > +
> > +define void @musttail_external() {
> > + musttail call void @external()
> > + ret void
> > +}
> > +; CHECK: musttail_external:
> > +; CHECK: movl external at GOT
> > +; CHECK: jmpl
> >
> >
> > _______________________________________________
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> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
>
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