[clang] [compiler-rt] [llvm] [XRay][RISCV] RISCV support for XRay (PR #117368)

[Min-Yih Hsu via cfe-commits]

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@@ -453,11 +475,71 @@ bool RISCVAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
   SetupMachineFunction(MF);
   emitFunctionBody();
 
+  // Emit the XRay table
+  emitXRayTable();
+
   if (EmittedOptionArch)
     RTS.emitDirectiveOptionPop();
   return false;
 }
 
+void RISCVAsmPrinter::LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr *MI) {
+  emitSled(MI, SledKind::FUNCTION_ENTER);
+}
+
+void RISCVAsmPrinter::LowerPATCHABLE_FUNCTION_EXIT(const MachineInstr *MI) {
+  emitSled(MI, SledKind::FUNCTION_EXIT);
+}
+
+void RISCVAsmPrinter::LowerPATCHABLE_TAIL_CALL(const MachineInstr *MI) {
+  emitSled(MI, SledKind::TAIL_CALL);
+}
+
+void RISCVAsmPrinter::emitSled(const MachineInstr *MI, SledKind Kind) {
+  // We want to emit the jump instruction and the nops constituting the sled.
+  // The format is as follows:
+  // .Lxray_sled_N
+  //   ALIGN
+  //   J .tmpN
+  //   29 or 37 C.NOP instructions
+  // .tmpN
+
+  // The following variable holds the count of the number of NOPs to be patched
+  // in for XRay instrumentation during compilation.
+  // Note that RV64 and RV32 each has a sled of 76 and 60 bytes, respectively.
+  // Assuming we're using JAL to jump to .tmpN, then we only need
+  // (76 - 4)/2 = 36 NOPs for RV64 and (60 - 4)/2 = 28 for RV32. However, there
+  // is a chance that we'll use C.JAL instead, so an additional NOP is needed.
+  const uint8_t NoopsInSledCount =
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mshockwave wrote:

Done.

https://github.com/llvm/llvm-project/pull/117368