https://github.com/zhouguangyuan0718 created https://github.com/llvm/llvm-project/pull/180242
Which is under discussion in https://github.com/llvm/llvm-project/issues/179036 Add new options -ffixed_r{8~15} for clang X86 target, like option "-ffixed_x" for RISCV/AArch64 target. Also, add target-feature +reserve-r{8~15} for the X86 backend. The registers which are specified reserved will not be used in RegAlloc/CalleeSave. Then the reserved registers can be maintained by user. It will be useful for the runtime/interpreter implementation. Other registers are used in specific instructions or mechanism, so they can't be reserved. >From 8a6dc960a50b708bed7948279c1f8e1f00e34d70 Mon Sep 17 00:00:00 2001 From: ZhouGuangyuan <[email protected]> Date: Sat, 7 Feb 2026 00:09:33 +0800 Subject: [PATCH] [X86] support reserve r8~r15 on X86_64 Add new options -ffixed_r{8~15} for clang X86 target, like option "-ffixed_x" for RISCV/AArch64 target. Also, add target-feature +reserve-r{8~15} for the X86 backend. The registers which are specified reserved will not be used in RegAlloc/CalleeSave. Then the reserved registers can be maintained by user. It will be useful for the runtime/interpreter implementation. Other registers are used in specific instructions or mechanism, so they can't be reserved. Signed-off-by: ZhouGuangyuan <[email protected]> --- clang/include/clang/Options/Options.td | 8 +- clang/lib/Basic/Targets/X86.h | 7 ++ clang/lib/Driver/ToolChains/Arch/X86.cpp | 14 ++++ clang/test/Driver/x86_64-fixed-r-register.c | 65 ++++++++++++++ llvm/lib/Target/X86/X86.td | 4 + llvm/lib/Target/X86/X86FrameLowering.cpp | 8 ++ llvm/lib/Target/X86/X86ISelLowering.cpp | 9 ++ llvm/lib/Target/X86/X86RegisterInfo.cpp | 11 +++ llvm/lib/Target/X86/X86Subtarget.cpp | 3 +- llvm/lib/Target/X86/X86Subtarget.h | 8 ++ llvm/test/CodeGen/X86/reserveRreg.ll | 93 +++++++++++++++++++++ 11 files changed, 227 insertions(+), 3 deletions(-) create mode 100644 clang/test/Driver/x86_64-fixed-r-register.c create mode 100644 llvm/test/CodeGen/X86/reserveRreg.ll diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td index 54e162c262a90..bd90f7b1cf0ec 100644 --- a/clang/include/clang/Options/Options.td +++ b/clang/include/clang/Options/Options.td @@ -5440,8 +5440,8 @@ def mrestrict_it: Flag<["-"], "mrestrict-it">, Group<m_arm_Features_Group>, def mno_restrict_it: Flag<["-"], "mno-restrict-it">, Group<m_arm_Features_Group>, HelpText<"Allow generation of complex IT blocks.">; def marm : Flag<["-"], "marm">, Alias<mno_thumb>; -def ffixed_r9 : Flag<["-"], "ffixed-r9">, Group<m_arm_Features_Group>, - HelpText<"Reserve the r9 register (ARM only)">; +def ffixed_r9 : Flag<["-"], "ffixed-r9">, Group<m_Group>, + HelpText<"Reserve the r9 register (ARM/x86_64 only)">; def mno_movt : Flag<["-"], "mno-movt">, Group<m_arm_Features_Group>, HelpText<"Disallow use of movt/movw pairs (ARM only)">; def mcrc : Flag<["-"], "mcrc">, Group<m_Group>, @@ -7077,6 +7077,10 @@ def mapxf : Flag<["-"], "mapxf">, Group<m_x86_Features_Group>; def mno_apxf : Flag<["-"], "mno-apxf">, Group<m_x86_Features_Group>; def mapx_inline_asm_use_gpr32 : Flag<["-"], "mapx-inline-asm-use-gpr32">, Group<m_Group>, HelpText<"Enable use of GPR32 in inline assembly for APX">; +foreach i = {8, 10-15} in + def ffixed_r#i : Flag<["-"], "ffixed-r"#i>, Group<m_Group>, + HelpText<"Reserve the r"#i#" register (x86_64 only)">; + } // let Flags = [TargetSpecific] // VE feature flags diff --git a/clang/lib/Basic/Targets/X86.h b/clang/lib/Basic/Targets/X86.h index 922e32906cd04..65617e4fcea21 100644 --- a/clang/lib/Basic/Targets/X86.h +++ b/clang/lib/Basic/Targets/X86.h @@ -807,6 +807,13 @@ class LLVM_LIBRARY_VISIBILITY X86_64TargetInfo : public X86TargetInfo { return true; } + StringRef Reg64 = RegName; + if (Reg64.back() == 'd' || Reg64.back() == 'w' || Reg64.back() == 'b') { + Reg64 = Reg64.substr(0, Reg64.size() - 1); + } + if (getTargetOpts().FeatureMap.lookup(("reserve-" + Reg64).str())) + return true; + // Check if the register is a 32-bit register the backend can handle. return X86TargetInfo::validateGlobalRegisterVariable(RegName, RegSize, HasSizeMismatch); diff --git a/clang/lib/Driver/ToolChains/Arch/X86.cpp b/clang/lib/Driver/ToolChains/Arch/X86.cpp index 61d512f9e093f..c4ccddffca9fa 100644 --- a/clang/lib/Driver/ToolChains/Arch/X86.cpp +++ b/clang/lib/Driver/ToolChains/Arch/X86.cpp @@ -332,4 +332,18 @@ void x86::getX86TargetFeatures(const Driver &D, const llvm::Triple &Triple, if (A->getOption().matches(options::OPT_m3dnow)) D.Diag(diag::warn_drv_clang_unsupported) << A->getAsString(Args); } + + // Handle features corresponding to "-ffixed-X" options +#define RESERVE_REG(REG) \ + if (Args.hasArg(options::OPT_ffixed_##REG)) \ + Features.push_back("+reserve-" #REG); + RESERVE_REG(r8) + RESERVE_REG(r9) + RESERVE_REG(r10) + RESERVE_REG(r11) + RESERVE_REG(r12) + RESERVE_REG(r13) + RESERVE_REG(r14) + RESERVE_REG(r15) +#undef RESERVE_REG } diff --git a/clang/test/Driver/x86_64-fixed-r-register.c b/clang/test/Driver/x86_64-fixed-r-register.c new file mode 100644 index 0000000000000..714db3fdfdc91 --- /dev/null +++ b/clang/test/Driver/x86_64-fixed-r-register.c @@ -0,0 +1,65 @@ +// RUN: %clang --target=x86_64-unknown-linux-gnu -ffixed-r8 -### %s 2> %t +// RUN: FileCheck --check-prefix=CHECK-FIXED-R8 < %t %s +// CHECK-FIXED-R8: "-target-feature" "+reserve-r8" + +// RUN: %clang --target=x86_64-unknown-linux-gnu -ffixed-r9 -### %s 2> %t +// RUN: FileCheck --check-prefix=CHECK-FIXED-R9 < %t %s +// CHECK-FIXED-R9: "-target-feature" "+reserve-r9" + +// RUN: %clang --target=x86_64-unknown-linux-gnu -ffixed-r10 -### %s 2> %t +// RUN: FileCheck --check-prefix=CHECK-FIXED-R10 < %t %s +// CHECK-FIXED-R10: "-target-feature" "+reserve-r10" + +// RUN: %clang --target=x86_64-unknown-linux-gnu -ffixed-r11 -### %s 2> %t +// RUN: FileCheck --check-prefix=CHECK-FIXED-R11 < %t %s +// CHECK-FIXED-R11: "-target-feature" "+reserve-r11" + +// RUN: %clang --target=x86_64-unknown-linux-gnu -ffixed-r12 -### %s 2> %t +// RUN: FileCheck --check-prefix=CHECK-FIXED-R12 < %t %s +// CHECK-FIXED-R12: "-target-feature" "+reserve-r12" + +// RUN: %clang --target=x86_64-unknown-linux-gnu -ffixed-r13 -### %s 2> %t +// RUN: FileCheck --check-prefix=CHECK-FIXED-R13 < %t %s +// CHECK-FIXED-R13: "-target-feature" "+reserve-r13" + +// RUN: %clang --target=x86_64-unknown-linux-gnu -ffixed-r14 -### %s 2> %t +// RUN: FileCheck --check-prefix=CHECK-FIXED-R14 < %t %s +// CHECK-FIXED-R14: "-target-feature" "+reserve-r14" + +// RUN: %clang --target=x86_64-unknown-linux-gnu -ffixed-r15 -### %s 2> %t +// RUN: FileCheck --check-prefix=CHECK-FIXED-R15 < %t %s +// CHECK-FIXED-R15: "-target-feature" "+reserve-r15" + +// Test multiple of reserve-r# options together. +// RUN: %clang --target=x86_64-unknown-linux-gnu \ +// RUN: -ffixed-r8 \ +// RUN: -ffixed-r9 \ +// RUN: -ffixed-r15 \ +// RUN: -### %s 2> %t +// RUN: FileCheck \ +// RUN: --check-prefix=CHECK-FIXED-R8 \ +// RUN: --check-prefix=CHECK-FIXED-R9 \ +// RUN: --check-prefix=CHECK-FIXED-R15 \ +// RUN: < %t %s + +// Test all reserve-r# options together. +// RUN: %clang --target=x86_64-unknown-linux-gnu \ +// RUN: -ffixed-r8 \ +// RUN: -ffixed-r9 \ +// RUN: -ffixed-r10 \ +// RUN: -ffixed-r11 \ +// RUN: -ffixed-r12 \ +// RUN: -ffixed-r13 \ +// RUN: -ffixed-r14 \ +// RUN: -ffixed-r15 \ +// RUN: -### %s 2> %t +// RUN: FileCheck \ +// RUN: --check-prefix=CHECK-FIXED-R8 \ +// RUN: --check-prefix=CHECK-FIXED-R9 \ +// RUN: --check-prefix=CHECK-FIXED-R10 \ +// RUN: --check-prefix=CHECK-FIXED-R11 \ +// RUN: --check-prefix=CHECK-FIXED-R12 \ +// RUN: --check-prefix=CHECK-FIXED-R13 \ +// RUN: --check-prefix=CHECK-FIXED-R14 \ +// RUN: --check-prefix=CHECK-FIXED-R15 \ +// RUN: < %t %s diff --git a/llvm/lib/Target/X86/X86.td b/llvm/lib/Target/X86/X86.td index 1b9a6ee2b4ef4..68491c42bddbd 100644 --- a/llvm/lib/Target/X86/X86.td +++ b/llvm/lib/Target/X86/X86.td @@ -32,6 +32,10 @@ def IsX32 : SubtargetFeature<"x32", "IsX32", "true", // X86 Subtarget ISA features //===----------------------------------------------------------------------===// +foreach i = {8-15} in + def FeatureReserveR#i : SubtargetFeature<"reserve-r"#i, "ReservedRReg[X86::R"#i#"]", "true", + "Reserve R"#i#", making it unavailable as a GPR">; + def FeatureX87 : SubtargetFeature<"x87","HasX87", "true", "Enable X87 float instructions">; diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp index 8bca6344d6521..8791470b0b5e1 100644 --- a/llvm/lib/Target/X86/X86FrameLowering.cpp +++ b/llvm/lib/Target/X86/X86FrameLowering.cpp @@ -3211,6 +3211,14 @@ void X86FrameLowering::determineCalleeSaves(MachineFunction &MF, BasePtr = getX86SubSuperRegister(BasePtr, 64); SavedRegs.set(BasePtr); } + if (STI.is64Bit()) { + for (int Reg = SavedRegs.find_first(); Reg != -1; + Reg = SavedRegs.find_next(Reg)) { + if (STI.isRegisterReservedByUser(Reg)) { + SavedRegs.reset(Reg); + } + } + } } static bool HasNestArgument(const MachineFunction *MF) { diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp index 3ec2bf9b19360..8e621a189b04d 100644 --- a/llvm/lib/Target/X86/X86ISelLowering.cpp +++ b/llvm/lib/Target/X86/X86ISelLowering.cpp @@ -28731,6 +28731,15 @@ Register X86TargetLowering::getRegisterByName(const char* RegName, LLT VT, } #endif } + if (Subtarget.is64Bit()) { + if (Reg) + return Reg; + + Reg = MatchRegisterName(RegName); + if (!Subtarget.isRegisterReservedByUser(Reg)) + reportFatalUsageError(Twine("Trying to obtain non-reserved register \"" + + StringRef(RegName) + "\".")); + } return Reg; } diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp index 72f38133e21ff..b78c4c0393c69 100644 --- a/llvm/lib/Target/X86/X86RegisterInfo.cpp +++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp @@ -515,6 +515,17 @@ BitVector X86RegisterInfo::getReservedRegs(const MachineFunction &MF) const { // Set the Shadow Stack Pointer as reserved. Reserved.set(X86::SSP); + auto &ST = MF.getSubtarget<X86Subtarget>(); + if (ST.is64Bit()) { + for (size_t Reg = 0; Reg < getNumRegs(); Reg++) { + // Set r# as reserved register if user required + if (ST.isRegisterReservedByUser(Reg)) { + for (const MCPhysReg &SubReg : subregs_inclusive(X86::RSP)) + Reserved.set(SubReg); + } + } + } + // Set the instruction pointer register and its aliases as reserved. for (const MCPhysReg &SubReg : subregs_inclusive(X86::RIP)) Reserved.set(SubReg); diff --git a/llvm/lib/Target/X86/X86Subtarget.cpp b/llvm/lib/Target/X86/X86Subtarget.cpp index 4e2e98410f325..f73ca37a45c07 100644 --- a/llvm/lib/Target/X86/X86Subtarget.cpp +++ b/llvm/lib/Target/X86/X86Subtarget.cpp @@ -317,7 +317,8 @@ X86Subtarget::X86Subtarget(const Triple &TT, StringRef CPU, StringRef TuneCPU, unsigned PreferVectorWidthOverride, unsigned RequiredVectorWidth) : X86GenSubtargetInfo(TT, CPU, TuneCPU, FS), - PICStyle(PICStyles::Style::None), TM(TM), TargetTriple(TT), + PICStyle(PICStyles::Style::None), TM(TM), + ReservedRReg(X86::NUM_TARGET_REGS), TargetTriple(TT), StackAlignOverride(StackAlignOverride), PreferVectorWidthOverride(PreferVectorWidthOverride), RequiredVectorWidth(RequiredVectorWidth), diff --git a/llvm/lib/Target/X86/X86Subtarget.h b/llvm/lib/Target/X86/X86Subtarget.h index 3b920bc4ef7c1..dd9a5de3030ed 100644 --- a/llvm/lib/Target/X86/X86Subtarget.h +++ b/llvm/lib/Target/X86/X86Subtarget.h @@ -17,6 +17,7 @@ #include "X86ISelLowering.h" #include "X86InstrInfo.h" #include "X86SelectionDAGInfo.h" +#include "llvm/ADT/BitVector.h" #include "llvm/CodeGen/TargetSubtargetInfo.h" #include "llvm/IR/CallingConv.h" #include "llvm/TargetParser/Triple.h" @@ -65,6 +66,9 @@ class X86Subtarget final : public X86GenSubtargetInfo { #define GET_SUBTARGETINFO_MACRO(ATTRIBUTE, DEFAULT, GETTER) \ bool ATTRIBUTE = DEFAULT; #include "X86GenSubtargetInfo.inc" + /// ReservedRReg R#i is not available as a general purpose register. + BitVector ReservedRReg; + /// The minimum alignment known to hold of the stack frame on /// entry to the function and which must be maintained by every function. Align stackAlignment = Align(4); @@ -155,6 +159,10 @@ class X86Subtarget final : public X86GenSubtargetInfo { const LegalizerInfo *getLegalizerInfo() const override; const RegisterBankInfo *getRegBankInfo() const override; + bool isRegisterReservedByUser(Register i) const override { + return ReservedRReg[i.id()]; + } + private: /// Initialize the full set of dependencies so we can use an initializer /// list for X86Subtarget. diff --git a/llvm/test/CodeGen/X86/reserveRreg.ll b/llvm/test/CodeGen/X86/reserveRreg.ll new file mode 100644 index 0000000000000..cfd80022e3cc4 --- /dev/null +++ b/llvm/test/CodeGen/X86/reserveRreg.ll @@ -0,0 +1,93 @@ +;; Check if manually reserved registers are always excluded from being saved by +;; the function prolog/epilog, even for callee-saved ones, as per GCC behavior. + +; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s + +define preserve_mostcc void @t8() "target-features"="+reserve-r8" { +; CHECK-LABEL: t8: +; CHECK: # %bb.0: +; CHECK-NEXT: movl $256, %r8d +; CHECK-NEXT: #APP +; CHECK-NEXT: #NO_APP +; CHECK-NEXT: ret + call i64 asm sideeffect "", "={r8},{r8}"(i64 256) + ret void +} + +define preserve_mostcc void @t9() "target-features"="+reserve-r9" { +; CHECK-LABEL: t9: +; CHECK: # %bb.0: +; CHECK-NEXT: movl $256, %r9d +; CHECK-NEXT: #APP +; CHECK-NEXT: #NO_APP +; CHECK-NEXT: ret + call i64 asm sideeffect "", "={r9},{r9}"(i64 256) + ret void +} + +define preserve_mostcc void @t10() "target-features"="+reserve-r10" { +; CHECK-LABEL: t10: +; CHECK: # %bb.0: +; CHECK-NEXT: movl $256, %r10d +; CHECK-NEXT: #APP +; CHECK-NEXT: #NO_APP +; CHECK-NEXT: ret + call i64 asm sideeffect "", "={r10},{r10}"(i64 256) + ret void +} + +define preserve_mostcc void @t11() "target-features"="+reserve-r11" { +; CHECK-LABEL: t11: +; CHECK: # %bb.0: +; CHECK-NEXT: movl $256, %r11d +; CHECK-NEXT: #APP +; CHECK-NEXT: #NO_APP +; CHECK-NEXT: ret + call i64 asm sideeffect "", "={r11},{r11}"(i64 256) + ret void +} + +define preserve_mostcc void @t12() "target-features"="+reserve-r12" { +; CHECK-LABEL: t12: +; CHECK: # %bb.0: +; CHECK-NEXT: movl $256, %r12d +; CHECK-NEXT: #APP +; CHECK-NEXT: #NO_APP +; CHECK-NEXT: ret + call i64 asm sideeffect "", "={r12},{r12}"(i64 256) + ret void +} + +define preserve_mostcc void @t13() "target-features"="+reserve-r13" { +; CHECK-LABEL: t13: +; CHECK: # %bb.0: +; CHECK-NEXT: movl $256, %r13d +; CHECK-NEXT: #APP +; CHECK-NEXT: #NO_APP +; CHECK-NEXT: ret + call i64 asm sideeffect "", "={r13},{r13}"(i64 256) + ret void +} + +define preserve_mostcc void @t14() "target-features"="+reserve-r14" { +; CHECK-LABEL: t14: +; CHECK: # %bb.0: +; CHECK-NEXT: movl $256, %r14d +; CHECK-NEXT: #APP +; CHECK-NEXT: #NO_APP +; CHECK-NEXT: ret + call i64 asm sideeffect "", "={r14},{r14}"(i64 256) + ret void +} + +define preserve_mostcc void @t15() "target-features"="+reserve-r15" { +; CHECK-LABEL: t15: +; CHECK: # %bb.0: +; CHECK-NEXT: movl $256, %r15d +; CHECK-NEXT: #APP +; CHECK-NEXT: #NO_APP +; CHECK-NEXT: ret + call i64 asm sideeffect "", "={r15},{r15}"(i64 256) + ret void +} + _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
