[RISCV] Remove -mattr=+no-rvc-hints (llvm#145138)

topperc · Anthony Tran · commit 0fb80704a005 · 2025-06-26T12:46:05.000-07:00
As far as I know binutils does not have a similar option and I don't
know of a reason we shouldn't accept the RVC hint instructions.

The wording in the spec in the past suggested that maybe these
weren't valid instruction names, but that's been modified recently.
diff --git a/llvm/docs/ReleaseNotes.md b/llvm/docs/ReleaseNotes.md
@@ -212,6 +212,7 @@ Changes to the RISC-V Backend
 * `-mtune=andes-45-series` was added.
 * Adds assembler support for the Andes `XAndesvbfhcvt` (Andes Vector BFLOAT16 Conversion extension).
 * `-mcpu=andes-ax45mpv` was added.
+* Removed -mattr=+no-rvc-hints that could be used to disable parsing and generation of RVC hints.
 
 Changes to the WebAssembly Backend
 ----------------------------------
diff --git a/llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp b/llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp
@@ -292,7 +292,7 @@ void RISCVAsmPrinter::emitNTLHint(const MachineInstr *MI) {
     NontemporalMode += 0b10;
 
   MCInst Hint;
-  if (STI->hasStdExtZca() && STI->enableRVCHintInstrs())
+  if (STI->hasStdExtZca())
     Hint.setOpcode(RISCV::C_ADD_HINT);
   else
     Hint.setOpcode(RISCV::ADD);
diff --git a/llvm/lib/Target/RISCV/RISCVFeatures.td b/llvm/lib/Target/RISCV/RISCVFeatures.td
@@ -373,13 +373,6 @@ def HasStdExtZhinx : Predicate<"Subtarget->hasStdExtZhinx()">,
 def NoStdExtZhinx : Predicate<"!Subtarget->hasStdExtZhinx()">;
 
 // Compressed Extensions
-def FeatureNoRVCHints
-    : SubtargetFeature<"no-rvc-hints", "EnableRVCHintInstrs", "false",
-                       "Disable RVC Hint Instructions.">;
-def HasRVCHints : Predicate<"Subtarget->enableRVCHintInstrs()">,
-                  AssemblerPredicate<(all_of(not FeatureNoRVCHints)),
-                                     "RVC Hint Instructions">;
-
 def FeatureStdExtZca
     : RISCVExtension<1, 0,
                      "part of the C extension, excluding compressed "
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
@@ -1726,7 +1726,7 @@ unsigned RISCVInstrInfo::getInstSizeInBytes(const MachineInstr &MI) const {
   if (!MI.memoperands_empty()) {
     MachineMemOperand *MMO = *(MI.memoperands_begin());
     if (STI.hasStdExtZihintntl() && MMO->isNonTemporal()) {
-      if (STI.hasStdExtZca() && STI.enableRVCHintInstrs()) {
+      if (STI.hasStdExtZca()) {
         if (isCompressibleInst(MI, STI))
           return 4; // c.ntl.all + c.load/c.store
         return 6;   // c.ntl.all + load/store
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoC.td b/llvm/lib/Target/RISCV/RISCVInstrInfoC.td
@@ -608,7 +608,7 @@ def C_UNIMP : RVInst16<(outs), (ins), "c.unimp", "", [], InstFormatOther>,
 // HINT Instructions
 //===----------------------------------------------------------------------===//
 
-let Predicates = [HasStdExtZca, HasRVCHints], hasSideEffects = 0, mayLoad = 0,
+let Predicates = [HasStdExtZca], hasSideEffects = 0, mayLoad = 0,
     mayStore = 0 in {
 
 def C_NOP_HINT : RVInst16CI<0b000, 0b01, (outs), (ins simm6nonzero:$imm),
@@ -691,24 +691,24 @@ def C_SRAI64_HINT : RVInst16CB<0b100, 0b01, (outs GPRC:$rd),
   let Inst{12} = 0;
 }
 
-} // Predicates = [HasStdExtZca, HasRVCHints], hasSideEffects = 0, mayLoad = 0,
+} // Predicates = [HasStdExtZca], hasSideEffects = 0, mayLoad = 0,
   // mayStore = 0
 
 //===----------------------------------------------------------------------===//
 // Assembler Pseudo Instructions
 //===----------------------------------------------------------------------===//
 
-let Predicates = [HasStdExtZca, HasRVCHints] in {
+let Predicates = [HasStdExtZca] in {
 // Just a different syntax for the c.nop hint: c.addi x0, simm6 vs c.nop simm6.
 def : InstAlias<"c.addi x0, $imm", (C_NOP_HINT simm6nonzero:$imm), 0>;
 }
 
-let Predicates = [HasStdExtC, HasRVCHints, HasStdExtZihintntl] in {
+let Predicates = [HasStdExtC, HasStdExtZihintntl] in {
 def : InstAlias<"c.ntl.p1", (C_ADD_HINT X0, X2)>;
 def : InstAlias<"c.ntl.pall", (C_ADD_HINT X0, X3)>;
 def : InstAlias<"c.ntl.s1", (C_ADD_HINT X0, X4)>;
 def : InstAlias<"c.ntl.all", (C_ADD_HINT X0, X5)>;
-} // Predicates = [HasStdExtC, HasRVCHints, HasStdExtZihintntl]
+} // Predicates = [HasStdExtC, HasStdExtZihintntl]
 
 let EmitPriority = 0 in {
 let Predicates = [HasStdExtZca] in {
diff --git a/llvm/test/CodeGen/RISCV/features-info.ll b/llvm/test/CodeGen/RISCV/features-info.ll
@@ -61,7 +61,6 @@
 ; CHECK-NEXT:   m                                - 'M' (Integer Multiplication and Division).
 ; CHECK-NEXT:   mips-p8700                       - MIPS p8700 processor.
 ; CHECK-NEXT:   no-default-unroll                - Disable default unroll preference..
-; CHECK-NEXT:   no-rvc-hints                     - Disable RVC Hint Instructions..
 ; CHECK-NEXT:   no-sink-splat-operands           - Disable sink splat operands to enable .vx, .vf,.wx, and .wf instructions.
 ; CHECK-NEXT:   no-trailing-seq-cst-fence        - Disable trailing fence for seq-cst store..
 ; CHECK-NEXT:   optimized-nf2-segment-load-store - vlseg2eN.v and vsseg2eN.v are implemented as a wide memory op and shuffle.
diff --git a/llvm/test/MC/Disassembler/RISCV/c_lui_disasm.txt b/llvm/test/MC/Disassembler/RISCV/c_lui_disasm.txt
@@ -10,265 +10,197 @@
 # RUN: llvm-mc --disassemble -triple=riscv32  -mattr=+c -mattr=+Zcmop \
 # RUN:     -M no-aliases --show-encoding < %s | \
 # RUN:   FileCheck --check-prefixes=GOOD,MOP %s
-#
-# RUN: llvm-mc --disassemble -triple=riscv32  -mattr=+c -mattr=+no-rvc-hints \
-# RUN:     -M no-aliases --show-encoding < %s 2>&1 | \
-# RUN:   FileCheck --check-prefix=NOHINTS %s
 
 # BAD: invalid instruction encoding
-# NOHINTS: invalid instruction encoding
 0x01 0x60
 
 # GOOD: c.lui zero, 1
-# NOHINTS: invalid instruction encoding
 0x05 0x60
 
 # GOOD: c.lui zero, 2
-# NOHINTS: invalid instruction encoding
 0x09 0x60
 
 # GOOD: c.lui zero, 3
-# NOHINTS: invalid instruction encoding
 0x0D 0x60
 
 # GOOD: c.lui zero, 4
-# NOHINTS: invalid instruction encoding
 0x11 0x060
 
 # GOOD: c.lui zero, 5
-# NOHINTS: invalid instruction encoding
 0x15 0x60
 
 # GOOD: c.lui zero, 6
-# NOHINTS: invalid instruction encoding
 0x19 0x60
 
 # GOOD: c.lui zero, 7
-# NOHINTS: invalid instruction encoding
 0x1D 0x60
 
 # GOOD: c.lui zero, 8
-# NOHINTS: invalid instruction encoding
 0x21 0x60
 
 # GOOD: c.lui zero, 9
-# NOHINTS: invalid instruction encoding
 0x25 0x60
 
 # GOOD: c.lui zero, 10
-# NOHINTS: invalid instruction encoding
 0x29 0x60
 
 # GOOD: c.lui zero, 11
-# NOHINTS: invalid instruction encoding
 0x2D 0x60
 
 # GOOD: c.lui zero, 12
-# NOHINTS: invalid instruction encoding
 0x31 0x60
 
 # GOOD: c.lui zero, 13
-# NOHINTS: invalid instruction encoding
 0x35 0x60
 
 # GOOD: c.lui zero, 14
-# NOHINTS: invalid instruction encoding
 0x39 0x60
 
 # GOOD: c.lui zero, 15
-# NOHINTS: invalid instruction encoding
 0x3D 0x60
 
 # GOOD: c.lui zero, 16
-# NOHINTS: invalid instruction encoding
 0x41 0x60
 
 # GOOD: c.lui zero, 17
-# NOHINTS: invalid instruction encoding
 0x45 0x60
 
 # GOOD: c.lui zero, 18
-# NOHINTS: invalid instruction encoding
 0x49 0x60
 
 # GOOD: c.lui zero, 19
-# NOHINTS: invalid instruction encoding
 0x4D 0x60
 
 # GOOD: c.lui zero, 20
-# NOHINTS: invalid instruction encoding
 0x51 0x60
 
 # GOOD: c.lui zero, 21
-# NOHINTS: invalid instruction encoding
 0x55 0x60
 
 # GOOD: c.lui zero, 22
-# NOHINTS: invalid instruction encoding
 0x59 0x60
 
 # GOOD: c.lui zero, 23
-# NOHINTS: invalid instruction encoding
 0x5D 0x60
 
 # GOOD: c.lui zero, 24
-# NOHINTS: invalid instruction encoding
 0x61 0x60
 
 # GOOD: c.lui zero, 25
-# NOHINTS: invalid instruction encoding
 0x65 0x60
 
 # GOOD: c.lui zero, 26
-# NOHINTS: invalid instruction encoding
 0x69 0x60
 
 # GOOD: c.lui zero, 27
-# NOHINTS: invalid instruction encoding
 0x6D 0x60
 
 # GOOD: c.lui zero, 28
-# NOHINTS: invalid instruction encoding
 0x71 0x60
 
 # GOOD: c.lui zero, 29
-# NOHINTS: invalid instruction encoding
 0x75 0x60
 
 # GOOD: c.lui zero, 30
-# NOHINTS: invalid instruction encoding
 0x79 0x60
 
 # GOOD: c.lui zero, 31
-# NOHINTS: invalid instruction encoding
 0x7D 0x60
 
 # GOOD: c.lui zero, 1048544
-# NOHINTS: invalid instruction encoding
 0x01 0x70
 
 # GOOD: c.lui zero, 1048545
-# NOHINTS: invalid instruction encoding
 0x05 0x70
 
 # GOOD: c.lui zero, 1048546
-# NOHINTS: invalid instruction encoding
 0x09 0x70
 
 # GOOD: c.lui zero, 1048547
-# NOHINTS: invalid instruction encoding
 0x0D 0x70
 
 # GOOD: c.lui zero, 1048548
-# NOHINTS: invalid instruction encoding
 0x11 0x70
 
 # GOOD: c.lui zero, 1048549
-# NOHINTS: invalid instruction encoding
 0x15 0x70
 
 # GOOD: c.lui zero, 1048550
-# NOHINTS: invalid instruction encoding
 0x19 0x70
 
 # GOOD: c.lui zero, 1048551
-# NOHINTS: invalid instruction encoding
 0x1D 0x70
 
 # GOOD: c.lui zero, 1048552
-# NOHINTS: invalid instruction encoding
 0x21 0x70
 
 # GOOD: c.lui zero, 1048553
-# NOHINTS: invalid instruction encoding
 0x25 0x70
 
 # GOOD: c.lui zero, 1048554
-# NOHINTS: invalid instruction encoding
 0x29 0x70
 
 # GOOD: c.lui zero, 1048555
-# NOHINTS: invalid instruction encoding
 0x2D 0x70
 
 # GOOD: c.lui zero, 1048556
-# NOHINTS: invalid instruction encoding
 0x31 0x70
 
 # GOOD: c.lui zero, 1048557
-# NOHINTS: invalid instruction encoding
 0x35 0x70
 
 # GOOD: c.lui zero, 1048558
-# NOHINTS: invalid instruction encoding
 0x39 0x70
 
 # GOOD: c.lui zero, 1048559
-# NOHINTS: invalid instruction encoding
 0x3D 0x70
 
 # GOOD: c.lui zero, 1048560
-# NOHINTS: invalid instruction encoding
 0x41 0x70
 
 # GOOD: c.lui zero, 1048561
-# NOHINTS: invalid instruction encoding
 0x45 0x70
 
 # GOOD: c.lui zero, 1048562
-# NOHINTS: invalid instruction encoding
 0x49 0x70
 
 # GOOD: c.lui zero, 1048563
-# NOHINTS: invalid instruction encoding
 0x4D 0x70
 
 # GOOD: c.lui zero, 1048564
-# NOHINTS: invalid instruction encoding
 0x51 0x70
 
 # GOOD: c.lui zero, 1048565
-# NOHINTS: invalid instruction encoding
 0x55 0x70
 
 # GOOD: c.lui zero, 1048566
-# NOHINTS: invalid instruction encoding
 0x59 0x70
 
 # GOOD: c.lui zero, 1048567
-# NOHINTS: invalid instruction encoding
 0x5D 0x70
 
 # GOOD: c.lui zero, 1048568
-# NOHINTS: invalid instruction encoding
 0x61 0x70
 
 # GOOD: c.lui zero, 1048569
-# NOHINTS: invalid instruction encoding
 0x65 0x70
 
 # GOOD: c.lui zero, 1048570
-# NOHINTS: invalid instruction encoding
 0x69 0x70
 
 # GOOD: c.lui zero, 1048571
-# NOHINTS: invalid instruction encoding
 0x6D 0x70
 
 # GOOD: c.lui zero, 1048572
-# NOHINTS: invalid instruction encoding
 0x71 0x70
 
 # GOOD: c.lui zero, 1048573
-# NOHINTS: invalid instruction encoding
 0x75 0x70
 
 # GOOD: c.lui zero, 1048574
-# NOHINTS: invalid instruction encoding
 0x79 0x70
 
 # GOOD: c.lui zero, 1048575
-# NOHINTS: invalid instruction encoding
 0x7D 0x70
 
 # BAD: invalid instruction encoding
diff --git a/llvm/test/MC/RISCV/rv32c-invalid.s b/llvm/test/MC/RISCV/rv32c-invalid.s
@@ -1,6 +1,6 @@
-# RUN: not llvm-mc -triple=riscv32 -mattr=+c -mattr=+no-rvc-hints < %s 2>&1 \
+# RUN: not llvm-mc -triple=riscv32 -mattr=+c < %s 2>&1 \
 # RUN:     | FileCheck %s
-# RUN: not llvm-mc -triple=riscv32 -mattr=+zca -mattr=+no-rvc-hints < %s 2>&1 \
+# RUN: not llvm-mc -triple=riscv32 -mattr=+zca < %s 2>&1 \
 # RUN:     | FileCheck %s
 
 ## GPRC
@@ -23,16 +23,10 @@ c.lwsp  x0, 4(sp) # CHECK: :[[@LINE]]:9: error: register must be a GPR excluding
 c.lwsp  zero, 4(sp) # CHECK: :[[@LINE]]:9: error: register must be a GPR excluding zero (x0)
 c.jr  x0 # CHECK: :[[@LINE]]:7: error: register must be a GPR excluding zero (x0)
 c.jalr  zero # CHECK: :[[@LINE]]:9: error: register must be a GPR excluding zero (x0)
-c.addi  x0, x0, 1 # CHECK: :[[@LINE]]:13: error: immediate must be zero
-c.li  zero, 2 # CHECK: :[[@LINE]]:1: error: instruction requires the following: RVC Hint Instructions{{$}}
-c.slli  zero, zero, 4 # CHECK: :[[@LINE]]:15: error: invalid operand for instruction
-c.mv  zero, s0 # CHECK: :[[@LINE]]:1: error: instruction requires the following: RVC Hint Instructions{{$}}
 c.mv  ra, x0 # CHECK: :[[@LINE]]:11: error: register must be a GPR excluding zero (x0)
 c.add  ra, ra, x0 # CHECK: :[[@LINE]]:16: error: invalid operand for instruction
-c.add  zero, zero, sp # CHECK: :[[@LINE]]:14: error: invalid operand for instruction
 
 ## GPRNoX0X2
-c.lui x0, 4 # CHECK: :[[@LINE]]:1: error: instruction requires the following: RVC Hint Instructions{{$}}
 c.lui x2, 4 # CHECK: :[[@LINE]]:7: error: register must be a GPR excluding zero (x0) and sp (x2){{$}}
 
 ## SP
@@ -57,7 +51,6 @@ c.andi a0, %lo(foo) # CHECK: :[[@LINE]]:12: error: immediate must be an integer
 c.andi a0, %hi(foo) # CHECK: :[[@LINE]]:12: error: immediate must be an integer in the range [-32, 31]
 
 ## simm6nonzero
-c.addi t0, 0 # CHECK: :[[@LINE]]:1: error: instruction requires the following: RVC Hint Instructions{{$}}
 c.addi t0, -33 # CHECK: :[[@LINE]]:12: error: immediate must be non-zero in the range [-32, 31]
 c.addi t0, 32 # CHECK: :[[@LINE]]:12: error: immediate must be non-zero in the range [-32, 31]
 c.addi t0, foo # CHECK: :[[@LINE]]:12: error: immediate must be non-zero in the range [-32, 31]
