[llvm] 62ba528 - [Systemz/z/OS] Centralize emitting the call type information

[Kai Nacke via llvm-commits]

Author: Kai Nacke
Date: 2022-02-14T12:00:50-05:00
New Revision: 62ba528a686924965b4cca7d140a2c148cca310f

URL: https://github.com/llvm/llvm-project/commit/62ba528a686924965b4cca7d140a2c148cca310f
DIFF: https://github.com/llvm/llvm-project/commit/62ba528a686924965b4cca7d140a2c148cca310f.diff

LOG: [Systemz/z/OS] Centralize emitting the call type information

With XPLINK, a no-op with information about the call type is emitted
after each call instruction. Centralizing it has the advantage that it is
easy to document all cases, and it makes it easier to extend it later
(e.g. dynamic stack allocation, 32 bit mode).
Also add a test checking the call types emitted so far.

Reviewed By: uweigand

Differential Revision: https://reviews.llvm.org/D119557

Added: 
    llvm/test/CodeGen/SystemZ/call-zos-02.ll

Modified: 
    llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp
    llvm/lib/Target/SystemZ/SystemZAsmPrinter.h

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp b/llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp
index 84b337685c148..5c255967bc870 100644
--- a/llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp
@@ -124,6 +124,18 @@ static MCInst lowerSubvectorStore(const MachineInstr *MI, unsigned Opcode) {
     .addImm(0);
 }
 
+// The XPLINK ABI requires that a no-op encoding the call type is emitted after
+// each call to a subroutine. This information can be used by the called
+// function to determine its entry point, e.g. for generating a backtrace. The
+// call type is encoded as a register number in the bcr instruction. See
+// enumeration CallType for the possible values.
+void SystemZAsmPrinter::emitCallInformation(CallType CT) {
+  EmitToStreamer(*OutStreamer,
+                 MCInstBuilder(SystemZ::BCRAsm)
+                     .addImm(0)
+                     .addReg(SystemZMC::GR64Regs[static_cast<unsigned>(CT)]));
+}
+
 void SystemZAsmPrinter::emitInstruction(const MachineInstr *MI) {
   SystemZMCInstLower Lower(MF->getContext(), *this);
   MCInst LoweredMI;
@@ -234,18 +246,14 @@ void SystemZAsmPrinter::emitInstruction(const MachineInstr *MI) {
                        .addReg(SystemZ::R7D)
                        .addExpr(Lower.getExpr(MI->getOperand(0),
                                               MCSymbolRefExpr::VK_PLT)));
-    EmitToStreamer(
-        *OutStreamer,
-        MCInstBuilder(SystemZ::BCRAsm).addImm(0).addReg(SystemZ::R3D));
+    emitCallInformation(CallType::BRASL7);
     return;
 
   case SystemZ::CallBASR_XPLINK64:
     EmitToStreamer(*OutStreamer, MCInstBuilder(SystemZ::BASR)
                                      .addReg(SystemZ::R7D)
                                      .addReg(MI->getOperand(0).getReg()));
-    EmitToStreamer(
-        *OutStreamer,
-        MCInstBuilder(SystemZ::BCRAsm).addImm(0).addReg(SystemZ::R0D));
+    emitCallInformation(CallType::BASR76);
     return;
 
   case SystemZ::CallBRASL:

diff  --git a/llvm/lib/Target/SystemZ/SystemZAsmPrinter.h b/llvm/lib/Target/SystemZ/SystemZAsmPrinter.h
index 80d68d1b93ff7..7839938f5ae5f 100644
--- a/llvm/lib/Target/SystemZ/SystemZAsmPrinter.h
+++ b/llvm/lib/Target/SystemZ/SystemZAsmPrinter.h
@@ -33,6 +33,18 @@ class LLVM_LIBRARY_VISIBILITY SystemZAsmPrinter : public AsmPrinter {
     return static_cast<SystemZTargetStreamer *>(TS);
   }
 
+  /// Call type information for XPLINK.
+  enum class CallType {
+    BASR76 = 0,   // b'x000' == BASR  r7,r6
+    BRAS7 = 1,    // b'x001' == BRAS  r7,ep
+    RESVD_2 = 2,  // b'x010'
+    BRASL7 = 3,   // b'x011' == BRASL r7,ep
+    RESVD_4 = 4,  // b'x100'
+    RESVD_5 = 5,  // b'x101'
+    BALR1415 = 6, // b'x110' == BALR  r14,r15
+    BASR33 = 7,   // b'x111' == BASR  r3,r3
+  };
+
 public:
   SystemZAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
       : AsmPrinter(TM, std::move(Streamer)), SM(*this) {}
@@ -54,6 +66,7 @@ class LLVM_LIBRARY_VISIBILITY SystemZAsmPrinter : public AsmPrinter {
   void emitFunctionEntryLabel() override;
 
 private:
+  void emitCallInformation(CallType CT);
   void LowerFENTRY_CALL(const MachineInstr &MI, SystemZMCInstLower &MCIL);
   void LowerSTACKMAP(const MachineInstr &MI);
   void LowerPATCHPOINT(const MachineInstr &MI, SystemZMCInstLower &Lower);

diff  --git a/llvm/test/CodeGen/SystemZ/call-zos-02.ll b/llvm/test/CodeGen/SystemZ/call-zos-02.ll
new file mode 100644
index 0000000000000..29e3e275bedc4
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/call-zos-02.ll
@@ -0,0 +1,17 @@
+; RUN: llc --mtriple=s390x-ibm-zos --show-mc-encoding < %s | FileCheck %s
+
+define internal signext i32 @caller() {
+entry:
+  ret i32 0
+}
+
+
+define hidden signext i32 @caller2() {
+entry:
+; CHECK-LABEL:   caller2:
+; CHECK:         brasl 7, caller at PLT   * encoding: [0xc0,0x75,A,A,A,A]
+; CHECK-NEXT:    * fixup A - offset: 2, value: caller at PLT+2, kind: FK_390_PC32DBL
+; CHECK-NEXT:    bcr     0, 3          * encoding: [0x07,0x03]
+  %call = call signext i32 @caller()
+  ret i32 %call
+}