[XRay][Arm] Repair XRay table emission on Arm32 and add tests to identify such problem earlier

[rSerge]

Summary

Emission of XRay table was occasionally disabled for Arm32, but this bug was not then detected because earlier (also by mistake) testing of XRay was occasionally disabled on 32-bit Arm targets. This patch should fix that problem and detect such problems in the future.
This patch is one of a series, see also

• https://reviews.llvm.org/D28623

[dberris]

LGTM -- thanks @rSerge.

[rSerge]

Please, note that this change can stay in mainline if https://reviews.llvm.org/D28623 is reverted because that one is real build-breaker.

[rSerge]

Just submitting the same changes trying to workaround a glitch in Arcanist...

[rSerge]

Again in mainline at revision 292516.

llvm/trunk/lib/Target/ARM/ARMAsmPrinter.cpp

if (Subtarget->isTargetCOFF()) {
     OutStreamer->EmitCOFFSymbolStorageClass(Scl);
     OutStreamer->EmitCOFFSymbolType(Type);
     OutStreamer->EndCOFFSymbolDef();
   }
 
   // Emit the rest of the function body.
   EmitFunctionBody();
 
+  // Emit the XRay table for this function.
+  emitXRayTable();
+
   // If we need V4T thumb mode Register Indirect Jump pads, emit them.
   // These are created per function, rather than per TU, since it's
   // relatively easy to exceed the thumb branch range within a TU.
   if (! ThumbIndirectPads.empty()) {
     OutStreamer->EmitAssemblerFlag(MCAF_Code16);
     EmitAlignment(1);
     for (unsigned i = 0, e = ThumbIndirectPads.size(); i < e; i++) {
       OutStreamer->EmitLabel(ThumbIndirectPads[i].second);

llvm/trunk/test/CodeGen/ARM/xray-armv6-attribute-instrumentation.ll

 ; CHECK-NEXT:  mov  r0, r0
 ; CHECK-NEXT:  mov  r0, r0
 ; CHECK-NEXT:  mov  r0, r0
 ; CHECK-NEXT:  mov  r0, r0
 ; CHECK-NEXT:  mov  r0, r0
 ; CHECK-LABEL: Ltmp1:
 ; CHECK-NEXT:  bx lr
 }
+; CHECK:       .p2align 4
+; CHECK-NEXT:  .long {{.*}}Lxray_synthetic_0
+; CHECK-NEXT:  .section {{.*}}xray_instr_map{{.*}}
+; CHECK-LABEL: Lxray_synthetic_0:
+; CHECK:       .long {{.*}}Lxray_sled_0
+; CHECK:       .long {{.*}}Lxray_sled_1

llvm/trunk/test/CodeGen/ARM/xray-armv7-attribute-instrumentation.ll

 ; CHECK-NEXT:  nop
 ; CHECK-NEXT:  nop
 ; CHECK-NEXT:  nop
 ; CHECK-NEXT:  nop
 ; CHECK-NEXT:  nop
 ; CHECK-LABEL: Ltmp1:
 ; CHECK-NEXT:  bx lr
 }
+; CHECK:       .p2align 4
+; CHECK-NEXT:  .long {{.*}}Lxray_synthetic_0
+; CHECK-NEXT:  .section {{.*}}xray_instr_map{{.*}}
+; CHECK-LABEL: Lxray_synthetic_0:
+; CHECK:       .long {{.*}}Lxray_sled_0
+; CHECK:       .long {{.*}}Lxray_sled_1