[ARM64EC 3/?] Mark reserved registers specific to ARM64EC ABI.

[efriedma]

Summary

Part of patchset to add initial support for ARM64EC.

I'm not completely sure I understand the reason for this restriction, but Microsoft documentation says that asynchronous signals clobber these registers, so we can't ever use them.

As far as I know, none of these registers have any hardcoded meaning, so reserving them shouldn't have any significant side-effects.

[mstorsjo]

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

331

The comment says v16-v31 but the code seems to go from 15 to 31 - is that a typo? (Based on the comment in the testcase, the code is right and the comment above is the one that is wrong.)

[efriedma]

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

331

Microsoft docs say v16-v31. Will fix.

[DavidSpickett]

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

331

Are you using the "B" name here so that all the various size registers up to "V" get marked as reserved too? (if not you could use "V" to match the comment)

[efriedma]

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

331

Yes, using the "B" name so markSuperRegs finds all the registers.

[efriedma]

Fix v15/v16 confusion

[dpaoliello]

You may also want to use the exiting llvm/test/CodeGen/AArch64/arm64-platform-reg.ll test case.

[efriedma]

Rebased

[efriedma]

https://reviews.llvm.org/rG4658366d95d5e398baad956225cc4ba339d5b037 . (phab didn't pick it up due to misspelling)

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

AArch64RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
   // FIXME: avoid re-calculating this every time.
   BitVector Reserved(getNumRegs());
   markSuperRegs(Reserved, AArch64::WSP);
   markSuperRegs(Reserved, AArch64::WZR);
 
   if (TFI->hasFP(MF) || TT.isOSDarwin())
     markSuperRegs(Reserved, AArch64::W29);
 
+  if (MF.getSubtarget<AArch64Subtarget>().isWindowsArm64EC()) {
+    // x13, x14, x23, x24, x28, and v16-v31 are clobbered by asynchronous
+    // signals, so we can't ever use them.
+    markSuperRegs(Reserved, AArch64::W13);
+    markSuperRegs(Reserved, AArch64::W14);
+    markSuperRegs(Reserved, AArch64::W23);
+    markSuperRegs(Reserved, AArch64::W24);
+    markSuperRegs(Reserved, AArch64::W28);
+    for (unsigned i = AArch64::B16; i <= AArch64::B31; ++i)
+      markSuperRegs(Reserved, i);
+  }
+
   for (size_t i = 0; i < AArch64::GPR32commonRegClass.getNumRegs(); ++i) {
     if (MF.getSubtarget<AArch64Subtarget>().isXRegisterReserved(i))
       markSuperRegs(Reserved, AArch64::GPR32commonRegClass.getRegister(i));
   }
 
   if (hasBasePointer(MF))
     markSuperRegs(Reserved, AArch64::W19);
 

llvm/lib/Target/AArch64/AArch64Subtarget.h

#include "AArch64GenSubtargetInfo.inc"
   bool isLittleEndian() const { return IsLittle; }
 
   bool isTargetDarwin() const { return TargetTriple.isOSDarwin(); }
   bool isTargetIOS() const { return TargetTriple.isiOS(); }
   bool isTargetLinux() const { return TargetTriple.isOSLinux(); }
   bool isTargetWindows() const { return TargetTriple.isOSWindows(); }
   bool isTargetAndroid() const { return TargetTriple.isAndroid(); }
   bool isTargetFuchsia() const { return TargetTriple.isOSFuchsia(); }
+  bool isWindowsArm64EC() const { return TargetTriple.isWindowsArm64EC(); }
 
   bool isTargetCOFF() const { return TargetTriple.isOSBinFormatCOFF(); }
   bool isTargetELF() const { return TargetTriple.isOSBinFormatELF(); }
   bool isTargetMachO() const { return TargetTriple.isOSBinFormatMachO(); }
 
   bool isTargetILP32() const {
     return TargetTriple.isArch32Bit() ||
            TargetTriple.getEnvironment() == Triple::GNUILP32;

llvm/test/CodeGen/AArch64/arm64ec-reservedregs.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=arm64ec-pc-windows-msvc < %s | FileCheck %s
+
+; Make sure we're reserving all the registers that are supposed to be
+; reserved. Integer regs x13, x15, x23, x24, x28. Float regs v16-v31.
+; We confirm this by ensuring that we spill if and only if none of the
+; unreserved registers are available.
+
+define i32 @no_int_regs(i32 %x) nounwind {
+; CHECK-LABEL: no_int_regs:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    stp x30, x29, [sp, #-80]! // 16-byte Folded Spill
+; CHECK-NEXT:    str x27, [sp, #16] // 8-byte Folded Spill
+; CHECK-NEXT:    stp x26, x25, [sp, #32] // 16-byte Folded Spill
+; CHECK-NEXT:    stp x22, x21, [sp, #48] // 16-byte Folded Spill
+; CHECK-NEXT:    stp x20, x19, [sp, #64] // 16-byte Folded Spill
+; CHECK-NEXT:    str w0, [sp, #28] // 4-byte Folded Spill
+; CHECK-NEXT:    //APP
+; CHECK-NEXT:    //NO_APP
+; CHECK-NEXT:    ldp x20, x19, [sp, #64] // 16-byte Folded Reload
+; CHECK-NEXT:    ldp x22, x21, [sp, #48] // 16-byte Folded Reload
+; CHECK-NEXT:    ldp x26, x25, [sp, #32] // 16-byte Folded Reload
+; CHECK-NEXT:    ldr w0, [sp, #28] // 4-byte Folded Reload
+; CHECK-NEXT:    ldr x27, [sp, #16] // 8-byte Folded Reload
+; CHECK-NEXT:    ldp x30, x29, [sp], #80 // 16-byte Folded Reload
+; CHECK-NEXT:    ret
+entry:
+  tail call void asm sideeffect "", "~{x0},~{x1},~{x2},~{x3},~{x4},~{x5},~{x6},~{x7},~{x8},~{x9},~{x10},~{x11},~{x12},~{x15},~{x16},~{x17},~{x19},~{x20},~{x21},~{x22},~{x25},~{x26},~{x27},~{fp},~{lr}"()
+  ret i32 %x
+}
+
+define i32 @one_int_reg(i32 %x) nounwind {
+; CHECK-LABEL: one_int_reg:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    stp x30, x29, [sp, #-80]! // 16-byte Folded Spill
+; CHECK-NEXT:    str x27, [sp, #16] // 8-byte Folded Spill
+; CHECK-NEXT:    mov w30, w0
+; CHECK-NEXT:    stp x26, x25, [sp, #32] // 16-byte Folded Spill
+; CHECK-NEXT:    stp x22, x21, [sp, #48] // 16-byte Folded Spill
+; CHECK-NEXT:    stp x20, x19, [sp, #64] // 16-byte Folded Spill
+; CHECK-NEXT:    //APP
+; CHECK-NEXT:    //NO_APP
+; CHECK-NEXT:    ldp x20, x19, [sp, #64] // 16-byte Folded Reload
+; CHECK-NEXT:    mov w0, w30
+; CHECK-NEXT:    ldp x22, x21, [sp, #48] // 16-byte Folded Reload
+; CHECK-NEXT:    ldp x26, x25, [sp, #32] // 16-byte Folded Reload
+; CHECK-NEXT:    ldr x27, [sp, #16] // 8-byte Folded Reload
+; CHECK-NEXT:    ldp x30, x29, [sp], #80 // 16-byte Folded Reload
+; CHECK-NEXT:    ret
+entry:
+  tail call void asm sideeffect "", "~{x0},~{x1},~{x2},~{x3},~{x4},~{x5},~{x6},~{x7},~{x8},~{x9},~{x10},~{x11},~{x12},~{x15},~{x16},~{x17},~{x19},~{x20},~{x21},~{x22},~{x25},~{x26},~{x27},~{fp}"()
+  ret i32 %x
+}
+
+define float @no_float_regs(float %x) nounwind {
+; CHECK-LABEL: no_float_regs:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    sub sp, sp, #80
+; CHECK-NEXT:    stp d15, d14, [sp, #16] // 16-byte Folded Spill
+; CHECK-NEXT:    stp d13, d12, [sp, #32] // 16-byte Folded Spill
+; CHECK-NEXT:    stp d11, d10, [sp, #48] // 16-byte Folded Spill
+; CHECK-NEXT:    stp d9, d8, [sp, #64] // 16-byte Folded Spill
+; CHECK-NEXT:    str s0, [sp, #12] // 4-byte Folded Spill
+; CHECK-NEXT:    //APP
+; CHECK-NEXT:    //NO_APP
+; CHECK-NEXT:    ldp d9, d8, [sp, #64] // 16-byte Folded Reload
+; CHECK-NEXT:    ldp d11, d10, [sp, #48] // 16-byte Folded Reload
+; CHECK-NEXT:    ldp d13, d12, [sp, #32] // 16-byte Folded Reload
+; CHECK-NEXT:    ldp d15, d14, [sp, #16] // 16-byte Folded Reload
+; CHECK-NEXT:    ldr s0, [sp, #12] // 4-byte Folded Reload
+; CHECK-NEXT:    add sp, sp, #80
+; CHECK-NEXT:    ret
+entry:
+  tail call void asm sideeffect "", "~{v0},~{v1},~{v2},~{v3},~{v4},~{v5},~{v6},~{v7},~{v8},~{v9},~{v10},~{v11},~{v12},~{v13},~{v14},~{v15}"()
+  ret float %x
+}
+
+define float @one_float_reg(float %x) nounwind {
+; CHECK-LABEL: one_float_reg:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    stp d15, d14, [sp, #-64]! // 16-byte Folded Spill
+; CHECK-NEXT:    stp d13, d12, [sp, #16] // 16-byte Folded Spill
+; CHECK-NEXT:    fmov s15, s0
+; CHECK-NEXT:    stp d11, d10, [sp, #32] // 16-byte Folded Spill
+; CHECK-NEXT:    stp d9, d8, [sp, #48] // 16-byte Folded Spill
+; CHECK-NEXT:    //APP
+; CHECK-NEXT:    //NO_APP
+; CHECK-NEXT:    ldp d9, d8, [sp, #48] // 16-byte Folded Reload
+; CHECK-NEXT:    fmov s0, s15
+; CHECK-NEXT:    ldp d11, d10, [sp, #32] // 16-byte Folded Reload
+; CHECK-NEXT:    ldp d13, d12, [sp, #16] // 16-byte Folded Reload
+; CHECK-NEXT:    ldp d15, d14, [sp], #64 // 16-byte Folded Reload
+; CHECK-NEXT:    ret
+entry:
+  tail call void asm sideeffect "", "~{v0},~{v1},~{v2},~{v3},~{v4},~{v5},~{v6},~{v7},~{v8},~{v9},~{v10},~{v11},~{v12},~{v13},~{v14}"()
+  ret float %x
+}
+