[NFCI][StaticDataLayout] Get rid of section prefix validation in codegen (llvm#162349)

The section prefix validation was initially added when global variable's
section prefix is only added in the codegen pass.

Now the optimizer pass MemProfUse can annotate data section prefix by
making use of data access profiles, so we can remove the validation.
Also calls `setSectionPrefix` which returns whether section prefix is
updated.

This is the 3rd patch as a split of
llvm#155337

Author: mingmingl-llvm

llvm/lib/CodeGen/StaticDataAnnotator.cpp

@@ -78,19 +78,8 @@ bool StaticDataAnnotator::runOnModule(Module &M) {
     if (!llvm::memprof::IsAnnotationOK(GV))
       continue;
 
-    // The implementation below assumes prior passes don't set section prefixes,
-    // and specifically do 'assign' rather than 'update'. So report error if a
-    // section prefix is already set.
-    if (auto maybeSectionPrefix = GV.getSectionPrefix();
-        maybeSectionPrefix && !maybeSectionPrefix->empty())
-      llvm::report_fatal_error("Global variable " + GV.getName() +
-                               " already has a section prefix " +
-                               *maybeSectionPrefix);
-
     StringRef SectionPrefix = SDPI->getConstantSectionPrefix(&GV, PSI);
-    if (SectionPrefix.empty())
-      continue;
-
+    // setSectionPrefix returns true if the section prefix is updated.
     Changed |= GV.setSectionPrefix(SectionPrefix);
   }
 

llvm/test/CodeGen/X86/global-variable-partition-with-dap.ll

@@ -1,16 +1,15 @@
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
-;; A minimal test case. llc will crash if global variables already has a section
-;; prefix. Subsequent PRs will expand on this test case to test the hotness
-;; reconciliation implementation.
-
-; RUN: not llc -mtriple=x86_64-unknown-linux-gnu -relocation-model=pic \
+;; A minimal test case. Subsequent PRs will expand on this test case
+;; (e.g., with more functions, variables and profiles) and test the hotness
+;; reconcillation implementation.
+; RUN: llc -mtriple=x86_64-unknown-linux-gnu -relocation-model=pic \
 ; RUN:     -partition-static-data-sections=true \
 ; RUN:     -data-sections=true  -unique-section-names=false \
-; RUN:     %s -o - 2>&1 | FileCheck %s --check-prefix=ERR
+; RUN:     %s -o - 2>&1 | FileCheck %s --check-prefix=IR
 
-; ERR: Global variable hot_bss already has a section prefix hot
+; IR: .section .bss.hot.,"aw"
 
 @hot_bss = internal global i32 0, !section_prefix !17