[ARM][MVE] Decoding of VMSR doesn't diagnose some unpredictable encodings

[MarkMurrayARM]

Summary

Decoding of VMSR doesn't diagnose some unpredictable encodings, as the unpredictable bits are not correctly set.

Diff-reduce this instruction's internals WRT VMRS so I can see the differences better. Mostly this is s/src/Rt/g.

Fill in the "should-be-(0)" bits.

Designate the Unpredictable{} bits for both VMRS and VMSR.

[ostannard]

LGTM with one style nit.

lib/Target/ARM/ARMInstrVFP.td

2412

These lines could be collapsed together:

let Inst{11-0} = 0b101000010000;

[MarkMurrayARM]

lib/Target/ARM/ARMInstrVFP.td

2412

Sure, that would be shorter, but this way matches the way the bits are described in the official public documentation.If future decodings start to use these bits, then diffs should be less disruptive.

Also, this way matches the existing VMRS instruction.

lib/Target/ARM/ARMInstrVFP.td

class MovFromVFP<bits<4> opc19_16, dag oops, dag iops, string opc, string asm,
   let Inst{27-20} = 0b11101111;
   let Inst{19-16} = opc19_16;
   let Inst{15-12} = Rt;
   let Inst{11-8}  = 0b1010;
   let Inst{7}     = 0;
   let Inst{6-5}   = 0b00;
   let Inst{4}     = 1;
   let Inst{3-0}   = 0b0000;
+  let Unpredictable{7-5} = 0b111;
+  let Unpredictable{3-0} = 0b1111;
 }
 
 let DecoderMethod = "DecodeForVMRSandVMSR" in {
  // APSR is the application level alias of CPSR. This FPSCR N, Z, C, V flags
  // to APSR.
  let Defs = [CPSR], Uses = [FPSCR_NZCV], Predicates = [HasFPRegs],
      Rt = 0b1111 /* apsr_nzcv */ in
  def FMSTAT : MovFromVFP<0b0001 /* fpscr */, (outs), (ins),

 // Move from ARM core register to VFP System Register.
 //
 
 class MovToVFP<bits<4> opc19_16, dag oops, dag iops, string opc, string asm,
                list<dag> pattern>:
   VFPAI<oops, iops, VFPMiscFrm, IIC_fpSTAT, opc, asm, pattern> {
 
   // Instruction operand.
-  bits<4> src;
-
-  // Encode instruction operand.
-  let Inst{15-12} = src;
+  bits<4> Rt;
 
   let Inst{27-20} = 0b11101110;
   let Inst{19-16} = opc19_16;
+  let Inst{15-12} = Rt;
   let Inst{11-8}  = 0b1010;
   let Inst{7}     = 0;
+  let Inst{6-5}   = 0b00;
   let Inst{4}     = 1;
+  let Inst{3-0}   = 0b0000;
   let Predicates = [HasVFP2];
+  let Unpredictable{7-5} = 0b111;
+  let Unpredictable{3-0} = 0b1111;
 }
 
 let DecoderMethod = "DecodeForVMRSandVMSR" in {
  let Defs = [FPSCR] in {
    let Predicates = [HasFPRegs] in
    // Application level GPR -> FPSCR
-   def VMSR : MovToVFP<0b0001 /* fpscr */, (outs), (ins GPRnopc:$src),
-                       "vmsr", "\tfpscr, $src",
-                       [(int_arm_set_fpscr GPRnopc:$src)]>;
+   def VMSR : MovToVFP<0b0001 /* fpscr */, (outs), (ins GPRnopc:$Rt),
+                       "vmsr", "\tfpscr, $Rt",
+                       [(int_arm_set_fpscr GPRnopc:$Rt)]>;
    // System level GPR -> FPEXC
-   def VMSR_FPEXC : MovToVFP<0b1000 /* fpexc */, (outs), (ins GPRnopc:$src),
-                               "vmsr", "\tfpexc, $src", []>;
+   def VMSR_FPEXC : MovToVFP<0b1000 /* fpexc */, (outs), (ins GPRnopc:$Rt),
+                               "vmsr", "\tfpexc, $Rt", []>;
    // System level GPR -> FPSID
-   def VMSR_FPSID : MovToVFP<0b0000 /* fpsid */, (outs), (ins GPRnopc:$src),
-                             "vmsr", "\tfpsid, $src", []>;
-   def VMSR_FPINST : MovToVFP<0b1001 /* fpinst */, (outs), (ins GPRnopc:$src),
-                              "vmsr", "\tfpinst, $src", []>;
-   def VMSR_FPINST2 : MovToVFP<0b1010 /* fpinst2 */, (outs), (ins GPRnopc:$src),
-                               "vmsr", "\tfpinst2, $src", []>;
+   def VMSR_FPSID : MovToVFP<0b0000 /* fpsid */, (outs), (ins GPRnopc:$Rt),
+                             "vmsr", "\tfpsid, $Rt", []>;
+   def VMSR_FPINST : MovToVFP<0b1001 /* fpinst */, (outs), (ins GPRnopc:$Rt),
+                              "vmsr", "\tfpinst, $Rt", []>;
+   def VMSR_FPINST2 : MovToVFP<0b1010 /* fpinst2 */, (outs), (ins GPRnopc:$Rt),
+                               "vmsr", "\tfpinst2, $Rt", []>;
  }
  let Predicates = [HasV8_1MMainline, Has8MSecExt] in {
    // System level GPR -> FPSCR with context saving for security extensions
-   def VMSR_FPCXTNS : MovToVFP<0b1110 /* fpcxtns */, (outs), (ins GPR:$src),
-                               "vmsr", "\tfpcxtns, $src", []>;
+   def VMSR_FPCXTNS : MovToVFP<0b1110 /* fpcxtns */, (outs), (ins GPR:$Rt),
+                               "vmsr", "\tfpcxtns, $Rt", []>;
  }
  let Predicates = [HasV8_1MMainline, Has8MSecExt] in {
    // System level GPR -> FPSCR with context saving for security extensions
-   def VMSR_FPCXTS : MovToVFP<0b1111 /* fpcxts */, (outs), (ins GPR:$src),
-                              "vmsr", "\tfpcxts, $src", []>;
+   def VMSR_FPCXTS : MovToVFP<0b1111 /* fpcxts */, (outs), (ins GPR:$Rt),
+                              "vmsr", "\tfpcxts, $Rt", []>;
  }
  let Predicates = [HasV8_1MMainline, HasFPRegs] in {
    // System level GPR -> FPSCR_NZCVQC
    def VMSR_FPSCR_NZCVQC
      : MovToVFP<0b0010 /* fpscr_nzcvqc */,
-                (outs cl_FPSCR_NZCV:$fpscr_out), (ins GPR:$src),
-                "vmsr", "\tfpscr_nzcvqc, $src", []>;
+                (outs cl_FPSCR_NZCV:$fpscr_out), (ins GPR:$Rt),
+                "vmsr", "\tfpscr_nzcvqc, $Rt", []>;
  }
 
  let Predicates = [HasV8_1MMainline, HasMVEInt] in {
    // System level GPR -> VPR/P0
    let Defs = [VPR] in
-   def VMSR_VPR : MovToVFP<0b1100 /* vpr */, (outs), (ins GPR:$src),
-                           "vmsr", "\tvpr, $src", []>;
+   def VMSR_VPR : MovToVFP<0b1100 /* vpr */, (outs), (ins GPR:$Rt),
+                           "vmsr", "\tvpr, $Rt", []>;
 
-   def VMSR_P0  : MovToVFP<0b1101 /* p0 */, (outs VCCR:$cond), (ins GPR:$src),
-                           "vmsr", "\tp0, $src", []>;
+   def VMSR_P0  : MovToVFP<0b1101 /* p0 */, (outs VCCR:$cond), (ins GPR:$Rt),
+                           "vmsr", "\tp0, $Rt", []>;
  }
 }
 
 //===----------------------------------------------------------------------===//
 // Misc.
 //
 
 // Materialize FP immediates. VFP3 only.

test/MC/Disassembler/ARM/vmrs-vmsr-invalid.txt

+# RUN: llvm-mc -triple=thumbv8.1m.main-none-eabi -mattr=+8msecext,+mve -show-encoding -disassemble < %s 2> %t | FileCheck --check-prefix=CHECK %s
+# RUN: FileCheck --check-prefix=STDERR < %t %s
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x11,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x12,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x13,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x14,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x15,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x16,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x17,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x18,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x19,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x1a,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x1b,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x1c,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x1d,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x1e,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x1f,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x30,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x50,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x70,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0x90,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0xb0,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0xd0,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmsr  fpscr, r0  @ encoding: [0xe1,0xee,0x10,0x0a]
+[0xe1,0xee,0xf0,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x11,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x12,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x13,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x14,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x15,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x16,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x17,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x18,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x19,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x1a,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x1b,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x1c,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x1d,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x1e,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x1f,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x30,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x50,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x70,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0x90,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0xb0,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0xd0,0x0a]
+
+# STDERR: [[@LINE+2]]:2: warning: potentially undefined instruction encoding
+# CHECK: vmrs  r0, fpscr  @ encoding: [0xf1,0xee,0x10,0x0a]
+[0xf1,0xee,0xf0,0x0a]