[XRay][AArch64] Implemented a test for the compile-time sleds emitted, and fixed a bug in the jump instruction

[rSerge]

Summary

This patch adds a test for the assembly code emitted with XRay instrumentation. It also fixes a bug where the operand of a jump instruction must be not the number of bytes to jump over, but rather the number of 4-byte instructions.

[dberris]

lib/Target/AArch64/AArch64AsmPrinter.cpp

228

Why not just write out the actual number of instructions? i.e. why not just: .addImm(8) ?

test/CodeGen/AArch64/xray-attribute-instrumentation.ll

26

You might want to make sure that the xray_instr_map section is written out and that you're seeing the references to the correct labels?

[rSerge]

lib/Target/AArch64/AArch64AsmPrinter.cpp

228

Ok, changing. I just thought that it's more convenient to think in bytes and show that that number is shifted by 2.

test/CodeGen/AArch64/xray-attribute-instrumentation.ll

26

Changing.

[rSerge]

Implemented the requests in code review comments.

lib/Target/AArch64/AArch64AsmPrinter.cpp

void AArch64AsmPrinter::EmitSled(const MachineInstr &MI, SledKind Kind)
   //   LDP X0, X30, [SP], #16 ; pop X0 and the link register from the stack
   //
   OutStreamer->EmitCodeAlignment(4);
   auto CurSled = OutContext.createTempSymbol("xray_sled_", true);
   OutStreamer->EmitLabel(CurSled);
   auto Target = OutContext.createTempSymbol();
 
   // Emit "B #32" instruction, which jumps over the next 28 bytes.
-  EmitToStreamer(*OutStreamer, MCInstBuilder(AArch64::B).addImm(32));
+  // The operand has to be the number of 4-byte instructions to jump over,
+  // including the current instruction.
+  EmitToStreamer(*OutStreamer, MCInstBuilder(AArch64::B).addImm(32 >> 2));
 
   for (int8_t I = 0; I < NoopsInSledCount; I++)
     EmitToStreamer(*OutStreamer, MCInstBuilder(AArch64::HINT).addImm(0));
 
   OutStreamer->EmitLabel(Target);
   recordSled(CurSled, MI, Kind);
 }
 

test/CodeGen/AArch64/xray-attribute-instrumentation.ll

+; RUN: llc -filetype=asm -o - -mtriple=aarch64-unknown-linux-gnu < %s | FileCheck %s
+
+define i32 @foo() nounwind noinline uwtable "function-instrument"="xray-always" {
+; CHECK-LABEL: Lxray_sled_0:
+; CHECK-NEXT:  b  #32
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-LABEL: Ltmp0:
+  ret i32 0
+; CHECK-LABEL: Lxray_sled_1:
+; CHECK-NEXT:  b  #32
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-NEXT:  nop
+; CHECK-LABEL: Ltmp1:
+; CHECK-NEXT:  ret
+}