[llvm] r367669 - Fix and test inter-procedural register allocation for ARM

Oliver Stannard via llvm-commits llvm-commits at lists.llvm.org
Fri Aug 2 03:23:05 PDT 2019


Author: ostannard
Date: Fri Aug  2 03:23:05 2019
New Revision: 367669

URL: http://llvm.org/viewvc/llvm-project?rev=367669&view=rev
Log:
Fix and test inter-procedural register allocation for ARM

- Avoid a crash when IPRA calls ARMFrameLowering::determineCalleeSaves
  with a null RegScavenger. Simply not updating the register scavenger
  is fine because IPRA only cares about the SavedRegs vector, the acutal
  code of the function has already been generated at this point.
- Add a new hook to TargetRegisterInfo to get the set of registers which
  can be clobbered inside a call, even if the compiler can see both
  sides, by linker-generated code.

Differential revision: https://reviews.llvm.org/D64908

Added:
    llvm/trunk/test/CodeGen/ARM/ipra.ll
Modified:
    llvm/trunk/include/llvm/CodeGen/TargetRegisterInfo.h
    llvm/trunk/lib/CodeGen/RegUsageInfoCollector.cpp
    llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp
    llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.h
    llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp

Modified: llvm/trunk/include/llvm/CodeGen/TargetRegisterInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/TargetRegisterInfo.h?rev=367669&r1=367668&r2=367669&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/TargetRegisterInfo.h (original)
+++ llvm/trunk/include/llvm/CodeGen/TargetRegisterInfo.h Fri Aug  2 03:23:05 2019
@@ -447,6 +447,14 @@ public:
     llvm_unreachable("target does not provide no preserved mask");
   }
 
+  /// Return a list of all of the registers which are clobbered "inside" a call
+  /// to the given function. For example, these might be needed for PLT
+  /// sequences of long-branch veneers.
+  virtual ArrayRef<MCPhysReg>
+  getIntraCallClobberedRegs(const MachineFunction *MF) const {
+    return {};
+  }
+
   /// Return true if all bits that are set in mask \p mask0 are also set in
   /// \p mask1.
   bool regmaskSubsetEqual(const uint32_t *mask0, const uint32_t *mask1) const;

Modified: llvm/trunk/lib/CodeGen/RegUsageInfoCollector.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegUsageInfoCollector.cpp?rev=367669&r1=367668&r2=367669&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/RegUsageInfoCollector.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegUsageInfoCollector.cpp Fri Aug  2 03:23:05 2019
@@ -142,6 +142,13 @@ bool RegUsageInfoCollector::runOnMachine
   auto SetRegAsDefined = [&RegMask] (unsigned Reg) {
     RegMask[Reg / 32] &= ~(1u << Reg % 32);
   };
+
+  // Some targets can clobber registers "inside" a call, typically in
+  // linker-generated code.
+  for (const MCPhysReg Reg : TRI->getIntraCallClobberedRegs(&MF))
+    for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+      SetRegAsDefined(*AI);
+
   // Scan all the physical registers. When a register is defined in the current
   // function set it and all the aliasing registers as defined in the regmask.
   // FIXME: Rewrite to use regunits.

Modified: llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp?rev=367669&r1=367668&r2=367669&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp Fri Aug  2 03:23:05 2019
@@ -174,6 +174,12 @@ ARMBaseRegisterInfo::getThisReturnPreser
                               : CSR_AAPCS_ThisReturn_RegMask;
 }
 
+ArrayRef<MCPhysReg> ARMBaseRegisterInfo::getIntraCallClobberedRegs(
+    const MachineFunction *MF) const {
+  static MCPhysReg IntraCallClobberedRegs[] = {ARM::R12};
+  return IntraCallClobberedRegs;
+}
+
 BitVector ARMBaseRegisterInfo::
 getReservedRegs(const MachineFunction &MF) const {
   const ARMSubtarget &STI = MF.getSubtarget<ARMSubtarget>();

Modified: llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.h?rev=367669&r1=367668&r2=367669&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.h (original)
+++ llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.h Fri Aug  2 03:23:05 2019
@@ -129,6 +129,9 @@ public:
   const uint32_t *getThisReturnPreservedMask(const MachineFunction &MF,
                                              CallingConv::ID) const;
 
+  ArrayRef<MCPhysReg>
+  getIntraCallClobberedRegs(const MachineFunction *MF) const override;
+
   BitVector getReservedRegs(const MachineFunction &MF) const override;
   bool isAsmClobberable(const MachineFunction &MF,
                        unsigned PhysReg) const override;

Modified: llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp?rev=367669&r1=367668&r2=367669&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp Fri Aug  2 03:23:05 2019
@@ -2080,9 +2080,8 @@ void ARMFrameLowering::determineCalleeSa
             ExtraCSSpill = true;
         }
       }
-      if (!ExtraCSSpill) {
+      if (!ExtraCSSpill && RS) {
         // Reserve a slot closest to SP or frame pointer.
-        assert(RS && "Register scavenging not provided");
         LLVM_DEBUG(dbgs() << "Reserving emergency spill slot\n");
         const TargetRegisterClass &RC = ARM::GPRRegClass;
         unsigned Size = TRI->getSpillSize(RC);

Added: llvm/trunk/test/CodeGen/ARM/ipra.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/ipra.ll?rev=367669&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/ipra.ll (added)
+++ llvm/trunk/test/CodeGen/ARM/ipra.ll Fri Aug  2 03:23:05 2019
@@ -0,0 +1,202 @@
+; RUN: llc -mtriple armv7a--none-eabi < %s              | FileCheck %s --check-prefix=CHECK --check-prefix=DISABLED
+; RUN: llc -mtriple armv7a--none-eabi < %s -enable-ipra | FileCheck %s --check-prefix=CHECK --check-prefix=ENABLED
+
+define void @leaf()  {
+entry:
+  tail call void asm sideeffect "", ""()
+  ret void
+}
+
+define void @leaf_r3() {
+entry:
+  tail call void asm sideeffect "", "~{r3}"()
+  ret void
+}
+
+define void @leaf_r4() {
+entry:
+  tail call void asm sideeffect "", "~{r4}"()
+  ret void
+}
+
+define void @leaf_s0() {
+entry:
+  tail call void asm sideeffect "", "~{s0}"()
+  ret void
+}
+
+define void @leaf_d0() {
+entry:
+  tail call void asm sideeffect "", "~{d0}"()
+  ret void
+}
+
+; r3 is normally caller-saved, but with IPRA we can see that it isn't used in
+; the callee, so can leave a live value in it.
+define void @test_r3_presrved() {
+; CHECK-LABEL: test_r3_presrved:
+entry:
+; CHECK: ASM1: r3
+; DISABLED: mov [[TEMP:r[0-9]+]], r3
+; ENABLED-NOT: r3
+; CHECK: bl      leaf
+; DISABLED: mov r3, [[TEMP]]
+; ENABLED-NOT: r3
+; CHECK: ASM2: r3
+  %a = tail call i32 asm sideeffect "// ASM1: $0", "={r3},0"(i32 undef)
+  tail call void @leaf()
+  %b = tail call i32 asm sideeffect "// ASM2: $0", "={r3},0"(i32 %a)
+  ret void
+}
+
+; Same as above, but r3 is clobbered in the callee, so it is clobbered by the
+; call as normal.
+define void @test_r3_clobbered() {
+; CHECK-LABEL: test_r3_clobbered:
+entry:
+; CHECK: ASM1: r3
+; CHECK: mov [[TEMP:r[0-9]+]], r3
+; CHECK: bl      leaf
+; CHECK: mov r3, [[TEMP]]
+; CHECK: ASM2: r3
+  %a = tail call i32 asm sideeffect "// ASM1: $0", "={r3},0"(i32 undef)
+  tail call void @leaf_r3()
+  %b = tail call i32 asm sideeffect "// ASM2: $0", "={r3},0"(i32 %a)
+  ret void
+}
+
+; r4 is a callee-saved register, so IPRA has no effect.
+define void @test_r4_preserved() {
+; CHECK-LABEL: test_r4_preserved:
+entry:
+; CHECK: ASM1: r4
+; CHECK-NOT: r4
+; CHECK: bl      leaf
+; CHECK-NOT: r4
+; CHECK: ASM2: r4
+  %a = tail call i32 asm sideeffect "// ASM1: $0", "={r4},0"(i32 undef)
+  tail call void @leaf()
+  %b = tail call i32 asm sideeffect "// ASM2: $0", "={r4},0"(i32 %a)
+  ret void
+}
+define void @test_r4_clobbered() {
+; CHECK-LABEL: test_r4_clobbered:
+entry:
+; CHECK: ASM1: r4
+; CHECK-NOT: r4
+; CHECK: bl      leaf_r4
+; CHECK-NOT: r4
+; CHECK: ASM2: r4
+  %a = tail call i32 asm sideeffect "// ASM1: $0", "={r4},0"(i32 undef)
+  tail call void @leaf_r4()
+  %b = tail call i32 asm sideeffect "// ASM2: $0", "={r4},0"(i32 %a)
+  ret void
+}
+
+; r12 is the intra-call scratch register, so we have to assume it is clobbered
+; even if we can see that the callee does not touch it.
+define void @test_r12() {
+; CHECK-LABEL: test_r12:
+entry:
+; CHECK: ASM1: r12
+; CHECK: mov [[TEMP:r[0-9]+]], r12
+; CHECK: bl      leaf
+; CHECK: mov r12, [[TEMP]]
+; CHECK: ASM2: r12
+  %a = tail call i32 asm sideeffect "// ASM1: $0", "={r12},0"(i32 undef)
+  tail call void @leaf()
+  %b = tail call i32 asm sideeffect "// ASM2: $0", "={r12},0"(i32 %a)
+  ret void
+}
+
+; s0 and d0 are caller-saved, IPRA allows us to keep them live in the caller if
+; the callee doesn't modify them.
+define void @test_s0_preserved() {
+; CHECK-LABEL: test_s0_preserved:
+entry:
+; CHECK: ASM1: s0
+; DISABLED: vmov.f32 [[TEMP:s[0-9]+]], s0
+; ENABLED-NOT: s0
+; CHECK: bl      leaf
+; DISABLED: vmov.f32 s0, [[TEMP]]
+; ENABLED-NOT: s0
+; CHECK: ASM2: s0
+  %a = tail call float asm sideeffect "// ASM1: $0", "={s0},0"(float undef)
+  tail call void @leaf()
+  %b = tail call float asm sideeffect "// ASM2: $0", "={s0},0"(float %a)
+  ret void
+}
+
+define void @test_s0_clobbered() {
+; CHECK-LABEL: test_s0_clobbered:
+entry:
+; CHECK: ASM1: s0
+; CHECK: vmov.f32 [[TEMP:s[0-9]+]], s0
+; CHECK: bl      leaf_s0
+; CHECK: vmov.f32 s0, [[TEMP]]
+; CHECK: ASM2: s0
+  %a = tail call float asm sideeffect "// ASM1: $0", "={s0},0"(float undef)
+  tail call void @leaf_s0()
+  %b = tail call float asm sideeffect "// ASM2: $0", "={s0},0"(float %a)
+  ret void
+}
+
+define void @test_d0_preserved() {
+; CHECK-LABEL: test_d0_preserved:
+entry:
+; CHECK: ASM1: d0
+; DISABLED: vmov.f64 [[TEMP:d[0-9]+]], d0
+; ENABLED-NOT: d0
+; CHECK: bl      leaf
+; DISABLED: vmov.f64 d0, [[TEMP]]
+; ENABLED-NOT: d0
+; CHECK: ASM2: d0
+  %a = tail call double asm sideeffect "// ASM1: $0", "={d0},0"(double undef)
+  tail call void @leaf()
+  %b = tail call double asm sideeffect "// ASM2: $0", "={d0},0"(double %a)
+  ret void
+}
+
+define void @test_d0_clobbered() {
+; CHECK-LABEL: test_d0_clobbered:
+entry:
+; CHECK: ASM1: d0
+; CHECK: vmov.f64 [[TEMP:d[0-9]+]], d0
+; CHECK: bl      leaf_d0
+; CHECK: vmov.f64 d0, [[TEMP]]
+; CHECK: ASM2: d0
+  %a = tail call double asm sideeffect "// ASM1: $0", "={d0},0"(double undef)
+  tail call void @leaf_d0()
+  %b = tail call double asm sideeffect "// ASM2: $0", "={d0},0"(double %a)
+  ret void
+}
+
+; s0 and d0 overlap, so clobbering one in the callee prevents the other from
+; being kept live across the call.
+define void @test_s0_clobber_d0() {
+; CHECK-LABEL: test_s0_clobber_d0:
+entry:
+; CHECK: ASM1: s0
+; CHECK: vmov.f32 [[TEMP:s[0-9]+]], s0
+; CHECK: bl      leaf_d0
+; CHECK: vmov.f32 s0, [[TEMP]]
+; CHECK: ASM2: s0
+  %a = tail call float asm sideeffect "// ASM1: $0", "={s0},0"(float undef)
+  tail call void @leaf_d0()
+  %b = tail call float asm sideeffect "// ASM2: $0", "={s0},0"(float %a)
+  ret void
+}
+
+define void @test_d0_clobber_s0() {
+; CHECK-LABEL: test_d0_clobber_s0:
+entry:
+; CHECK: ASM1: d0
+; CHECK: vmov.f64 [[TEMP:d[0-9]+]], d0
+; CHECK: bl      leaf_s0
+; CHECK: vmov.f64 d0, [[TEMP]]
+; CHECK: ASM2: d0
+  %a = tail call double asm sideeffect "// ASM1: $0", "={d0},0"(double undef)
+  tail call void @leaf_s0()
+  %b = tail call double asm sideeffect "// ASM2: $0", "={d0},0"(double %a)
+  ret void
+}




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