[SystemZ][z/OS] Fix incorrect codegen for ADA_ENTRY pseudo instruction (#101415)

The current MCInstBuilder for generating an ALGFI when loading something
from the ADA is incorrect and will crash the compiler.

r0 must also be excluded from the registers returned as the result,
since it is treated as the value "0" on z/OS.

Also add some tests to properly test the paths where LLILF and ALGFI are
generated.

---------

Co-authored-by: Tony Tao <[email protected]>

Author: tltao

llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp

@@ -346,9 +346,10 @@ void SystemZAsmPrinter::emitInstruction(const MachineInstr *MI) {
             *OutStreamer,
             MCInstBuilder(SystemZ::LLILF).addReg(TargetReg).addImm(Disp));
       } else
-        EmitToStreamer(
-            *OutStreamer,
-            MCInstBuilder(SystemZ::ALGFI).addReg(TargetReg).addImm(Disp));
+        EmitToStreamer(*OutStreamer, MCInstBuilder(SystemZ::ALGFI)
+                                         .addReg(TargetReg)
+                                         .addReg(TargetReg)
+                                         .addImm(Disp));
       Disp = 0;
       Op = Op0;
     }

llvm/lib/Target/SystemZ/SystemZInstrInfo.td

@@ -298,13 +298,13 @@ let Predicates = [IsTargetXPLINK64] in {
   }
 
   let hasNoSchedulingInfo = 1, Defs = [CC] in {
-    def ADA_ENTRY : Alias<12, (outs GR64:$Reg), (ins adasym:$addr,
+    def ADA_ENTRY : Alias<12, (outs ADDR64:$Reg), (ins adasym:$addr,
                               ADDR64:$ADA, imm64:$Offset),
                             [(set i64:$Reg, (z_ada_entry i64:$addr,
                               i64:$ADA, i64:$Offset))]>;
   }
   let mayLoad = 1, AddedComplexity = 20, hasNoSchedulingInfo = 1, Defs = [CC] in {
-    def ADA_ENTRY_VALUE : Alias<12, (outs GR64:$Reg), (ins adasym:$addr,
+    def ADA_ENTRY_VALUE : Alias<12, (outs ADDR64:$Reg), (ins adasym:$addr,
                               ADDR64:$ADA, imm64:$Offset),
                             [(set i64:$Reg, (z_load (z_ada_entry
                               iPTR:$addr, iPTR:$ADA, i64:$Offset)))]>;

llvm/test/CodeGen/SystemZ/Large/large-ada-01.py

@@ -0,0 +1,30 @@
+# Test code generation for retrieving function descriptors
+# from the ADA when the ADA is extremely large and forces the
+# generation of a different instruction sequence
+# RUN: %python %s | llc -mtriple=s390x-ibm-zos -O2 | FileCheck %s
+
+# CHECK: llilf	1, {{[0-9]+}}
+# CHECK-NEXT: la	1, 0(1,8)
+
+from __future__ import print_function
+
+num_calls = 35000
+
+print("define hidden signext i32 @main() {")
+print("entry:")
+
+for i in range(num_calls):
+    print("  call void @foo%d()" % i)
+
+print("  call void @bar(ptr noundef @foo)")
+print("ret i32 0")
+print("}")
+
+for i in range(num_calls):
+    print("declare void @foo%d(...)" % i)
+
+print("declare void @bar(ptr noundef)")
+print("define internal void @foo() {")
+print("entry:")
+print("  ret void")
+print("  }")

llvm/test/CodeGen/SystemZ/Large/large-ada-02.py

@@ -0,0 +1,33 @@
+# Test code generation for retrieving function descriptors
+# from the ADA when the ADA is extremely large and forces the
+# generation of a different instruction sequence
+# RUN: %python %s | llc -mtriple=s390x-ibm-zos -O2 | FileCheck %s
+
+# CHECK: algfi	8, {{[0-9]+}}
+# CHECK: la	8, 0(8)
+
+from __future__ import print_function
+
+num_calls = 35000
+
+print("define hidden signext i32 @main() {")
+print("entry:")
+
+for i in range(num_calls):
+    print("  call void @foo%d()" % i)
+
+# This is added to force the use of register r8 to generate
+# la 8, 0(8) which generates the algfi instruction
+print('%0 = call ptr asm " LGR $0,$1\0A", "=r,{r8}"(ptr nonnull @foo)')
+print("  call void @bar(ptr noundef %0)")
+print("ret i32 0")
+print("}")
+
+for i in range(num_calls):
+    print("declare void @foo%d(...)" % i)
+
+print("declare void @bar(ptr noundef)")
+print("define internal void @foo() {")
+print("entry:")
+print("  ret void")
+print("  }")