[RISCV] Support resumable non-maskable interrupt handlers (#148134)

futog · lenary · web-flow · commit 1454db130a7e · 2025-08-04T10:54:50.000+02:00
The `rnmi` interrupt attribute value has been added for the `Smrnmi`
extension.

---------

Co-authored-by: Sam Elliott &lt;sam@lenary.co.uk&gt;
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
@@ -198,6 +198,9 @@ LoongArch Support
 RISC-V Support
 ^^^^^^^^^^^^^^
 
+- Add support for `__attribute__((interrupt("rnmi")))` to be used with the `Smrnmi` extension.
+  With this the `Smrnmi` extension is fully supported.
+
 CUDA/HIP Language Changes
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
@@ -2361,6 +2361,7 @@ def RISCVInterrupt : InheritableAttr, TargetSpecificAttr<TargetRISCV> {
                                    [
                                      "supervisor",
                                      "machine",
+                                     "rnmi",
                                      "qci-nest",
                                      "qci-nonest",
                                      "SiFive-CLIC-preemptible",
@@ -2369,6 +2370,7 @@ def RISCVInterrupt : InheritableAttr, TargetSpecificAttr<TargetRISCV> {
                                    [
                                      "supervisor",
                                      "machine",
+                                     "rnmi",
                                      "qcinest",
                                      "qcinonest",
                                      "SiFiveCLICPreemptible",
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
@@ -2905,10 +2905,13 @@ the backend to generate appropriate function entry/exit code so that it can be
 used directly as an interrupt service routine.
 
 Permissible values for this parameter are ``machine``, ``supervisor``,
-``qci-nest``, ``qci-nonest``, ``SiFive-CLIC-preemptible``, and
+``rnmi``, ``qci-nest``, ``qci-nonest``, ``SiFive-CLIC-preemptible``, and
 ``SiFive-CLIC-stack-swap``. If there is no parameter, then it defaults to
 ``machine``.
 
+The ``rnmi`` value is used for resumable non-maskable interrupts. It requires the
+standard Smrnmi extension.
+
 The ``qci-nest`` and ``qci-nonest`` values require Qualcomm's Xqciint extension
 and are used for Machine-mode Interrupts and Machine-mode Non-maskable
 interrupts. These use the following instructions from Xqciint to save and
diff --git a/clang/lib/CodeGen/Targets/RISCV.cpp b/clang/lib/CodeGen/Targets/RISCV.cpp
@@ -817,6 +817,9 @@ class RISCVTargetCodeGenInfo : public TargetCodeGenInfo {
       case RISCVInterruptAttr::supervisor:
         Kind = "supervisor";
         break;
+      case RISCVInterruptAttr::rnmi:
+        Kind = "rnmi";
+        break;
       case RISCVInterruptAttr::qcinest:
         Kind = "qci-nest";
         break;
diff --git a/clang/lib/Sema/SemaRISCV.cpp b/clang/lib/Sema/SemaRISCV.cpp
@@ -1552,9 +1552,11 @@ void SemaRISCV::handleInterruptAttr(Decl *D, const ParsedAttr &AL) {
       HasSiFiveCLICType = true;
       break;
     case RISCVInterruptAttr::supervisor:
+    case RISCVInterruptAttr::rnmi:
     case RISCVInterruptAttr::qcinest:
     case RISCVInterruptAttr::qcinonest:
-      // "supervisor" and "qci-(no)nest" cannot be combined with any other types
+      // "supervisor", "rnmi" and "qci-(no)nest" cannot be combined with any
+      // other types
       HasUnaryType = true;
       break;
     }
@@ -1608,6 +1610,14 @@ void SemaRISCV::handleInterruptAttr(Decl *D, const ParsedAttr &AL) {
         return;
       }
     } break;
+    case RISCVInterruptAttr::rnmi: {
+      if (!HasFeature("smrnmi")) {
+        Diag(AL.getLoc(),
+             diag::err_riscv_attribute_interrupt_requires_extension)
+            << RISCVInterruptAttr::ConvertInterruptTypeToStr(Type) << "Smrnmi";
+        return;
+      }
+    } break;
     default:
       break;
     }
diff --git a/clang/test/Sema/riscv-interrupt-attr-rnmi.c b/clang/test/Sema/riscv-interrupt-attr-rnmi.c
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -triple riscv32-unknown-elf -target-feature +smrnmi -emit-llvm -DCHECK_IR < %s | FileCheck %s
+// RUN: %clang_cc1 %s -triple riscv32-unknown-elf -target-feature +smrnmi -verify=enabled,both -fsyntax-only
+// RUN: %clang_cc1 %s -triple riscv32-unknown-elf -verify=disabled,both -fsyntax-only
+// RUN: %clang_cc1 %s -triple riscv32-unknown-elf -target-feature -srnmi -verify=disabled,both -fsyntax-only
+
+#if defined(CHECK_IR)
+// CHECK-LABEL: foo_rnmi_interrupt() #0
+// CHECK: ret void
+__attribute__((interrupt("rnmi")))
+void foo_rnmi_interrupt(void) {}
+
+// CHECK-LABEL: @foo_rnmi_rnmi_interrupt() #0
+// CHECK: ret void
+__attribute__((interrupt("rnmi", "rnmi")))
+void foo_rnmi_rnmi_interrupt(void) {}
+
+// CHECK: attributes #0
+// CHECK: "interrupt"="rnmi"
+#else
+
+__attribute__((interrupt("rnmi"))) void test_rnmi(void) {} // disabled-error {{RISC-V 'interrupt' attribute 'rnmi' requires extension 'Smrnmi'}}
+__attribute__((interrupt("rnmi", "rnmi"))) void test_rnmi_rnmi(void) {} // disabled-error {{RISC-V 'interrupt' attribute 'rnmi' requires extension 'Smrnmi'}}
+
+__attribute__((interrupt("rnmi", "supervisor"))) void foo_rnmi_supervisor(void) {}  // both-error {{RISC-V 'interrupt' attribute contains invalid combination of interrupt types}}
+__attribute__((interrupt("rnmi", "machine"))) void foo_rnmi_machine(void) {}  // both-error {{RISC-V 'interrupt' attribute contains invalid combination of interrupt types}}
+
+__attribute__((interrupt("RNMI"))) void test_RNMI(void) {} // both-warning {{'interrupt' attribute argument not supported: "RNMI"}}
+#endif
diff --git a/llvm/docs/RISCVUsage.rst b/llvm/docs/RISCVUsage.rst
@@ -136,7 +136,7 @@ on support follow.
      ``Smepmp``        Supported
      ``Smmpm``         Supported
      ``Smnpm``         Supported
-     ``Smrnmi``        Assembly Support
+     ``Smrnmi``        Supported
      ``Smstateen``     Assembly Support
      ``Ssaia``         Supported
      ``Ssccfg``        Supported
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -22550,6 +22550,7 @@ SDValue RISCVTargetLowering::LowerFormalArguments(
     constexpr StringLiteral SupportedInterruptKinds[] = {
         "machine",
         "supervisor",
+        "rnmi",
         "qci-nest",
         "qci-nonest",
         "SiFive-CLIC-preemptible",
@@ -22567,6 +22568,8 @@ SDValue RISCVTargetLowering::LowerFormalArguments(
       reportFatalUsageError(
           "'SiFive-CLIC-*' interrupt kinds require XSfmclic extension");
 
+    if (Kind == "rnmi" && !Subtarget.hasStdExtSmrnmi())
+      reportFatalUsageError("'rnmi' interrupt kind requires Srnmi extension");
     const TargetFrameLowering *TFI = Subtarget.getFrameLowering();
     if (Kind.starts_with("SiFive-CLIC-preemptible") && TFI->hasFP(MF))
       reportFatalUsageError("'SiFive-CLIC-preemptible' interrupt kinds cannot "
@@ -23212,7 +23215,11 @@ RISCVTargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
 
     if (Kind == "supervisor")
       RetOpc = RISCVISD::SRET_GLUE;
-    else if (Kind == "qci-nest" || Kind == "qci-nonest") {
+    else if (Kind == "rnmi") {
+      assert(STI.hasFeature(RISCV::FeatureStdExtSmrnmi) &&
+             "Need Smrnmi extension for rnmi");
+      RetOpc = RISCVISD::MNRET_GLUE;
+    } else if (Kind == "qci-nest" || Kind == "qci-nonest") {
       assert(STI.hasFeature(RISCV::FeatureVendorXqciint) &&
              "Need Xqciint for qci-(no)nest");
       RetOpc = RISCVISD::QC_C_MILEAVERET_GLUE;
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.td b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
@@ -75,6 +75,8 @@ def riscv_sret_glue : RVSDNode<"SRET_GLUE", SDTNone,
                                [SDNPHasChain, SDNPOptInGlue]>;
 def riscv_mret_glue : RVSDNode<"MRET_GLUE", SDTNone,
                                [SDNPHasChain, SDNPOptInGlue]>;
+def riscv_mnret_glue : RVSDNode<"MNRET_GLUE", SDTNone,
+                                [SDNPHasChain, SDNPOptInGlue]>;
 def riscv_mileaveret_glue : RVSDNode<"QC_C_MILEAVERET_GLUE", SDTNone,
                                      [SDNPHasChain, SDNPOptInGlue]>;
 
@@ -935,7 +937,6 @@ def MRET : Priv<"mret", 0b0011000>, Sched<[]> {
   let rs1 = 0;
   let rs2 = 0b00010;
 }
-} // isBarrier = 1, isReturn = 1, isTerminator = 1
 
 let Predicates = [HasStdExtSmrnmi] in {
 def MNRET : Priv<"mnret", 0b0111000>, Sched<[]> {
@@ -944,6 +945,8 @@ def MNRET : Priv<"mnret", 0b0111000>, Sched<[]> {
   let rs2 = 0b00010;
 }
 }// Predicates = [HasStdExtSmrnmi]
+} // isBarrier = 1, isReturn = 1, isTerminator = 1
+
 
 def WFI : Priv<"wfi", 0b0001000>, Sched<[]> {
   let rd = 0;
@@ -1801,6 +1804,8 @@ def : Pat<(riscv_call texternalsym:$func), (PseudoCALL texternalsym:$func)>;
 
 def : Pat<(riscv_sret_glue), (SRET)>;
 def : Pat<(riscv_mret_glue), (MRET)>;
+let Predicates = [HasStdExtSmrnmi] in
+def : Pat<(riscv_mnret_glue), (MNRET)>;
 
 let isCall = 1, Defs = [X1] in {
 let Predicates = [NoStdExtZicfilp] in
diff --git a/llvm/test/CodeGen/RISCV/rnmi-interrupt-attr-error.ll b/llvm/test/CodeGen/RISCV/rnmi-interrupt-attr-error.ll
@@ -0,0 +1,9 @@
+; RUN: not llc -mtriple riscv32-unknown-elf -mattr=-smrnmi -o - %s 2>&1 \
+; RUN:   | FileCheck %s
+; RUN: not llc -mtriple riscv64-unknown-elf -mattr=-smrnmi -o - %s 2>&1 \
+; RUN:   | FileCheck %s
+
+; CHECK: LLVM ERROR: 'rnmi' interrupt kind requires Srnmi extension
+define void @test_rnmi() "interrupt"="rnmi" {
+  ret void
+}
diff --git a/llvm/test/CodeGen/RISCV/rnmi-interrupt-attr.ll b/llvm/test/CodeGen/RISCV/rnmi-interrupt-attr.ll
