[XRay] Make the xray_instr_map section specification more correct

Summary:
We also add a test to show what currently happens when we create a
section per function and emit an xray_instr_map. This illustrates the
relationship (or lack thereof) between the per-function section and the
xray_instr_map section.

We also change the code generation slightly so that we don't always
create group sections, but rather only do so if a function where the
table is associated with is in a group.

Also in this change:

  - Remove the "merge" flag on the xray_instr_map section.
  - Test that we're generating the right table for comdat and non-comdat functions.

Reviewers: echristo, majnemer

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D23104

llvm-svn: 277580

1 files changed, 11 insertions, 4 deletions

diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 906e3427b2f..18f9b3e2e2a 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -1096,11 +1096,18 @@ void X86AsmPrinter::EmitXRayTable() {
   if (Sleds.empty())
     return;
   if (Subtarget->isTargetELF()) {
-    auto *Section = OutContext.getELFSection(
-        "xray_instr_map", ELF::SHT_PROGBITS,
-        ELF::SHF_ALLOC | ELF::SHF_GROUP | ELF::SHF_MERGE, 0,
-        CurrentFnSym->getName());
     auto PrevSection = OutStreamer->getCurrentSectionOnly();
+    auto Fn = MF->getFunction();
+    MCSection *Section = nullptr;
+    if (Fn->hasComdat()) {
+      Section = OutContext.getELFSection("xray_instr_map", ELF::SHT_PROGBITS,
+                                         ELF::SHF_ALLOC | ELF::SHF_GROUP, 0,
+                                         Fn->getComdat()->getName());
+      OutStreamer->SwitchSection(Section);
+    } else {
+      Section = OutContext.getELFSection("xray_instr_map", ELF::SHT_PROGBITS,
+                                         ELF::SHF_ALLOC);
+    }
     OutStreamer->SwitchSection(Section);
     for (const auto &Sled : Sleds) {
       OutStreamer->EmitSymbolValue(Sled.Sled, 8);