diff options
author | Reid Kleckner <rnk@google.com> | 2018-02-14 00:22:20 +0000 |
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committer | Reid Kleckner <rnk@google.com> | 2018-02-14 00:22:20 +0000 |
commit | 1d4c94e1d4e803a0196cce93600496f85b0b5144 (patch) | |
tree | b1179471f50c03938389dee6eed5292ed94a45e8 | |
parent | ca89cbee8817c489d7d9cbf6d2371b8d722016c4 (diff) |
Merging r325049:
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r325049 | rnk | 2018-02-13 12:47:49 -0800 (Tue, 13 Feb 2018) | 17 lines
[X86] Use EDI for retpoline when no scratch regs are left
Summary:
Instead of solving the hard problem of how to pass the callee to the indirect
jump thunk without a register, just use a CSR. At a call boundary, there's
nothing stopping us from using a CSR to hold the callee as long as we save and
restore it in the prologue.
Also, add tests for this mregparm=3 case. I wrote execution tests for
__llvm_retpoline_push, but they never got committed as lit tests, either
because I never rewrote them or because they got lost in merge conflicts.
Reviewers: chandlerc, dwmw2
Subscribers: javed.absar, kristof.beyls, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D43214
------------------------------------------------------------------------
git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_60@325084 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r-- | lib/Target/X86/X86ISelLowering.cpp | 50 | ||||
-rw-r--r-- | lib/Target/X86/X86RetpolineThunks.cpp | 42 | ||||
-rw-r--r-- | test/CodeGen/X86/retpoline-regparm.ll | 42 | ||||
-rw-r--r-- | test/CodeGen/X86/retpoline.ll | 14 |
4 files changed, 76 insertions, 72 deletions
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp index d036e49a447..3cd5a0f738b 100644 --- a/lib/Target/X86/X86ISelLowering.cpp +++ b/lib/Target/X86/X86ISelLowering.cpp @@ -27109,9 +27109,6 @@ static const char *getRetpolineSymbol(const X86Subtarget &Subtarget, // attempt to help out kernels and other systems where duplicating the // thunks is costly. switch (Reg) { - case 0: - assert(!Subtarget.is64Bit() && "R11 should always be available on x64"); - return "__x86_indirect_thunk"; case X86::EAX: assert(!Subtarget.is64Bit() && "Should not be using a 32-bit thunk!"); return "__x86_indirect_thunk_eax"; @@ -27121,6 +27118,9 @@ static const char *getRetpolineSymbol(const X86Subtarget &Subtarget, case X86::EDX: assert(!Subtarget.is64Bit() && "Should not be using a 32-bit thunk!"); return "__x86_indirect_thunk_edx"; + case X86::EDI: + assert(!Subtarget.is64Bit() && "Should not be using a 32-bit thunk!"); + return "__x86_indirect_thunk_edi"; case X86::R11: assert(Subtarget.is64Bit() && "Should not be using a 64-bit thunk!"); return "__x86_indirect_thunk_r11"; @@ -27130,9 +27130,6 @@ static const char *getRetpolineSymbol(const X86Subtarget &Subtarget, // When targeting an internal COMDAT thunk use an LLVM-specific name. switch (Reg) { - case 0: - assert(!Subtarget.is64Bit() && "R11 should always be available on x64"); - return "__llvm_retpoline_push"; case X86::EAX: assert(!Subtarget.is64Bit() && "Should not be using a 32-bit thunk!"); return "__llvm_retpoline_eax"; @@ -27142,6 +27139,9 @@ static const char *getRetpolineSymbol(const X86Subtarget &Subtarget, case X86::EDX: assert(!Subtarget.is64Bit() && "Should not be using a 32-bit thunk!"); return "__llvm_retpoline_edx"; + case X86::EDI: + assert(!Subtarget.is64Bit() && "Should not be using a 32-bit thunk!"); + return "__llvm_retpoline_edi"; case X86::R11: assert(Subtarget.is64Bit() && "Should not be using a 64-bit thunk!"); return "__llvm_retpoline_r11"; @@ -27163,15 +27163,13 @@ X86TargetLowering::EmitLoweredRetpoline(MachineInstr &MI, // just use R11, but we scan for uses anyway to ensure we don't generate // incorrect code. On 32-bit, we use one of EAX, ECX, or EDX that isn't // already a register use operand to the call to hold the callee. If none - // are available, push the callee instead. This is less efficient, but is - // necessary for functions using 3 regparms. Such function calls are - // (currently) not eligible for tail call optimization, because there is no - // scratch register available to hold the address of the callee. + // are available, use EDI instead. EDI is chosen because EBX is the PIC base + // register and ESI is the base pointer to realigned stack frames with VLAs. SmallVector<unsigned, 3> AvailableRegs; if (Subtarget.is64Bit()) AvailableRegs.push_back(X86::R11); else - AvailableRegs.append({X86::EAX, X86::ECX, X86::EDX}); + AvailableRegs.append({X86::EAX, X86::ECX, X86::EDX, X86::EDI}); // Zero out any registers that are already used. for (const auto &MO : MI.operands()) { @@ -27189,30 +27187,18 @@ X86TargetLowering::EmitLoweredRetpoline(MachineInstr &MI, break; } } + if (!AvailableReg) + report_fatal_error("calling convention incompatible with retpoline, no " + "available registers"); const char *Symbol = getRetpolineSymbol(Subtarget, AvailableReg); - if (AvailableReg == 0) { - // No register available. Use PUSH. This must not be a tailcall, and this - // must not be x64. - if (Subtarget.is64Bit()) - report_fatal_error( - "Cannot make an indirect call on x86-64 using both retpoline and a " - "calling convention that preservers r11"); - if (Opc != X86::CALLpcrel32) - report_fatal_error("Cannot make an indirect tail call on x86 using " - "retpoline without a preserved register"); - BuildMI(*BB, MI, DL, TII->get(X86::PUSH32r)).addReg(CalleeVReg); - MI.getOperand(0).ChangeToES(Symbol); - MI.setDesc(TII->get(Opc)); - } else { - BuildMI(*BB, MI, DL, TII->get(TargetOpcode::COPY), AvailableReg) - .addReg(CalleeVReg); - MI.getOperand(0).ChangeToES(Symbol); - MI.setDesc(TII->get(Opc)); - MachineInstrBuilder(*BB->getParent(), &MI) - .addReg(AvailableReg, RegState::Implicit | RegState::Kill); - } + BuildMI(*BB, MI, DL, TII->get(TargetOpcode::COPY), AvailableReg) + .addReg(CalleeVReg); + MI.getOperand(0).ChangeToES(Symbol); + MI.setDesc(TII->get(Opc)); + MachineInstrBuilder(*BB->getParent(), &MI) + .addReg(AvailableReg, RegState::Implicit | RegState::Kill); return BB; } diff --git a/lib/Target/X86/X86RetpolineThunks.cpp b/lib/Target/X86/X86RetpolineThunks.cpp index 223fa577149..59ace3f19fc 100644 --- a/lib/Target/X86/X86RetpolineThunks.cpp +++ b/lib/Target/X86/X86RetpolineThunks.cpp @@ -43,7 +43,7 @@ static const char R11ThunkName[] = "__llvm_retpoline_r11"; static const char EAXThunkName[] = "__llvm_retpoline_eax"; static const char ECXThunkName[] = "__llvm_retpoline_ecx"; static const char EDXThunkName[] = "__llvm_retpoline_edx"; -static const char PushThunkName[] = "__llvm_retpoline_push"; +static const char EDIThunkName[] = "__llvm_retpoline_edi"; namespace { class X86RetpolineThunks : public MachineFunctionPass { @@ -127,7 +127,7 @@ bool X86RetpolineThunks::runOnMachineFunction(MachineFunction &MF) { createThunkFunction(M, R11ThunkName); else for (StringRef Name : - {EAXThunkName, ECXThunkName, EDXThunkName, PushThunkName}) + {EAXThunkName, ECXThunkName, EDXThunkName, EDIThunkName}) createThunkFunction(M, Name); InsertedThunks = true; return true; @@ -151,9 +151,8 @@ bool X86RetpolineThunks::runOnMachineFunction(MachineFunction &MF) { populateThunk(MF, X86::R11); } else { // For 32-bit targets we need to emit a collection of thunks for various - // possible scratch registers as well as a fallback that is used when - // there are no scratch registers and assumes the retpoline target has - // been pushed. + // possible scratch registers as well as a fallback that uses EDI, which is + // normally callee saved. // __llvm_retpoline_eax: // calll .Leax_call_target // .Leax_capture_spec: @@ -174,32 +173,18 @@ bool X86RetpolineThunks::runOnMachineFunction(MachineFunction &MF) { // movl %edx, (%esp) // retl // - // This last one is a bit more special and so needs a little extra - // handling. - // __llvm_retpoline_push: - // calll .Lpush_call_target - // .Lpush_capture_spec: - // pause - // lfence - // jmp .Lpush_capture_spec - // .align 16 - // .Lpush_call_target: - // # Clear pause_loop return address. - // addl $4, %esp - // # Top of stack words are: Callee, RA. Exchange Callee and RA. - // pushl 4(%esp) # Push callee - // pushl 4(%esp) # Push RA - // popl 8(%esp) # Pop RA to final RA - // popl (%esp) # Pop callee to next top of stack - // retl # Ret to callee + // __llvm_retpoline_edi: + // ... # Same setup + // movl %edi, (%esp) + // retl if (MF.getName() == EAXThunkName) populateThunk(MF, X86::EAX); else if (MF.getName() == ECXThunkName) populateThunk(MF, X86::ECX); else if (MF.getName() == EDXThunkName) populateThunk(MF, X86::EDX); - else if (MF.getName() == PushThunkName) - populateThunk(MF); + else if (MF.getName() == EDIThunkName) + populateThunk(MF, X86::EDI); else llvm_unreachable("Invalid thunk name on x86-32!"); } @@ -301,11 +286,6 @@ void X86RetpolineThunks::populateThunk(MachineFunction &MF, CaptureSpec->addSuccessor(CaptureSpec); CallTarget->setAlignment(4); - if (Reg) { - insertRegReturnAddrClobber(*CallTarget, *Reg); - } else { - assert(!Is64Bit && "We only support non-reg thunks on 32-bit x86!"); - insert32BitPushReturnAddrClobber(*CallTarget); - } + insertRegReturnAddrClobber(*CallTarget, *Reg); BuildMI(CallTarget, DebugLoc(), TII->get(RetOpc)); } diff --git a/test/CodeGen/X86/retpoline-regparm.ll b/test/CodeGen/X86/retpoline-regparm.ll new file mode 100644 index 00000000000..13b32740b28 --- /dev/null +++ b/test/CodeGen/X86/retpoline-regparm.ll @@ -0,0 +1,42 @@ +; RUN: llc -mtriple=i686-linux < %s | FileCheck --implicit-check-not="jmp.*\*" --implicit-check-not="call.*\*" %s + +; Test 32-bit retpoline when -mregparm=3 is used. This case is interesting +; because there are no available scratch registers. The Linux kernel builds +; with -mregparm=3, so we need to support it. TCO should fail because we need +; to restore EDI. + +define void @call_edi(void (i32, i32, i32)* %fp) #0 { +entry: + tail call void %fp(i32 inreg 0, i32 inreg 0, i32 inreg 0) + ret void +} + +; CHECK-LABEL: call_edi: +; EDI is used, so it must be saved. +; CHECK: pushl %edi +; CHECK-DAG: xorl %eax, %eax +; CHECK-DAG: xorl %edx, %edx +; CHECK-DAG: xorl %ecx, %ecx +; CHECK-DAG: movl {{.*}}, %edi +; CHECK: calll __llvm_retpoline_edi +; CHECK: popl %edi +; CHECK: retl + +define void @edi_external(void (i32, i32, i32)* %fp) #1 { +entry: + tail call void %fp(i32 inreg 0, i32 inreg 0, i32 inreg 0) + ret void +} + +; CHECK-LABEL: edi_external: +; CHECK: pushl %edi +; CHECK-DAG: xorl %eax, %eax +; CHECK-DAG: xorl %edx, %edx +; CHECK-DAG: xorl %ecx, %ecx +; CHECK-DAG: movl {{.*}}, %edi +; CHECK: calll __x86_indirect_thunk_edi +; CHECK: popl %edi +; CHECK: retl + +attributes #0 = { "target-features"="+retpoline" } +attributes #1 = { "target-features"="+retpoline-external-thunk" } diff --git a/test/CodeGen/X86/retpoline.ll b/test/CodeGen/X86/retpoline.ll index 57d3388b812..477609e2d10 100644 --- a/test/CodeGen/X86/retpoline.ll +++ b/test/CodeGen/X86/retpoline.ll @@ -340,10 +340,10 @@ latch: ; X86-NEXT: movl %edx, (%esp) ; X86-NEXT: retl ; -; X86-LABEL: .section .text.__llvm_retpoline_push,{{.*}},__llvm_retpoline_push,comdat -; X86-NEXT: .hidden __llvm_retpoline_push -; X86-NEXT: .weak __llvm_retpoline_push -; X86: __llvm_retpoline_push: +; X86-LABEL: .section .text.__llvm_retpoline_edi,{{.*}},__llvm_retpoline_edi,comdat +; X86-NEXT: .hidden __llvm_retpoline_edi +; X86-NEXT: .weak __llvm_retpoline_edi +; X86: __llvm_retpoline_edi: ; X86-NEXT: # {{.*}} # %entry ; X86-NEXT: calll [[CALL_TARGET:.*]] ; X86-NEXT: [[CAPTURE_SPEC:.*]]: # Block address taken @@ -355,11 +355,7 @@ latch: ; X86-NEXT: .p2align 4, 0x90 ; X86-NEXT: [[CALL_TARGET]]: # Block address taken ; X86-NEXT: # %entry -; X86-NEXT: addl $4, %esp -; X86-NEXT: pushl 4(%esp) -; X86-NEXT: pushl 4(%esp) -; X86-NEXT: popl 8(%esp) -; X86-NEXT: popl (%esp) +; X86-NEXT: movl %edi, (%esp) ; X86-NEXT: retl |