[memprof] Add a test to verify callstack order.

[snehasish]

Summary

We add to ensure that we are observing the correct callstack order in memprof
during symbolization. There was some confusion whether the order of
DIFrame objects were reversed but in reality the leaf function is at
index 0 so no code changes are required.

[snehasish]

Rebase, lint and fix test invocation.

[tejohnson]

llvm/test/tools/llvm-profdata/memprof-inline.test

39

These are printed during a debug run of what tool and with what options?

[snehasish]

Address comments.

[snehasish]

Updated the test documentation. PTAL, thanks!

[tejohnson]

lgtm

llvm/lib/ProfileData/RawMemProfReader.cpp

for (const uint64_t VAddr : Entry.getSecond()) {
       if (DI.getFrame(0).FunctionName == DILineInfo::BadString ||
           isRuntimePath(DI.getFrame(0).FileName)) {
         AllVAddrsToDiscard.insert(VAddr);
         continue;
       }
 
       for (size_t I = 0; I < DI.getNumberOfFrames(); I++) {
         const auto &Frame = DI.getFrame(I);
+        LLVM_DEBUG(
+            // Print out the name to guid mapping for debugging.
+            llvm::dbgs() << "FunctionName: " << Frame.FunctionName << " GUID: "
+                         << Function::getGUID(trimSuffix(Frame.FunctionName))
+                         << "\n";);
         SymbolizedFrame[VAddr].emplace_back(
             // We use the function guid which we expect to be a uint64_t. At
             // this time, it is the lower 64 bits of the md5 of the function
             // name. Any suffix with .llvm. is trimmed since these are added by
             // thinLTO global promotion. At the time the profile is consumed,
             // these suffixes will not be present.
             Function::getGUID(trimSuffix(Frame.FunctionName)),
             Frame.Line - Frame.StartLine, Frame.Column,

llvm/test/tools/llvm-profdata/memprof-inline.test

+REQUIRES: x86_64-linux
+
+The input raw profile test has been generated from the following source code:
+
+```
+#include <stdlib.h>
+#include <string.h>
+
+__attribute__((always_inline))
+void qux(int x) {
+  char *ptr = malloc(x);
+  memset(ptr, 0, x);
+  free(ptr);
+}
+
+__attribute__((noinline))
+void foo(int x){ qux(x); }
+
+__attribute__((noinline))
+void bar(int x) { foo(x); }
+
+int main(int argc, char **argv) {
+  bar(argc);
+  return 0;
+}
+```
+
+Compile and run with the following commands:
+
+```
+bin/clang -fuse-ld=lld -Wl,--no-rosegment -gmlt -fdebug-info-for-profiling \
+          -fmemory-profile -mno-omit-leaf-frame-pointer -fno-omit-frame-pointer \
+          -fno-optimize-sibling-calls -m64 -Wl,-build-id inline.c -o memprof-inline.exe
+
+env MEMPROF_OPTIONS=log_path=stdout ./memprof-inline.exe > inline.memprofraw
+```
+
+From a debug run we collect the name to guid mappings to ensure that the
+ordering we observe is as expected.
+
+```
+build-dbg/bin/llvm-profdata show --memory --debug-only=memprof \
+          inline.memprofraw --profiled-binary memprof-inline.exe
+
+FunctionName: qux GUID: 15505678318020221912
+FunctionName: foo GUID: 6699318081062747564
+FunctionName: bar GUID: 16434608426314478903
+FunctionName: main GUID: 15822663052811949562
+
+[..omit output here which is checked below..]
+```
+
+RUN: llvm-profdata show --memory %p/Inputs/inline.memprofraw --profiled-binary %p/Inputs/memprof-inline.exe
+
+CHECK:  MemprofProfile:
+CHECK-NEXT:  -
+CHECK-NEXT:  Header:
+CHECK-NEXT:    Version: 1
+CHECK-NEXT:    TotalSizeBytes: 880
+CHECK-NEXT:    NumSegments: 9
+CHECK-NEXT:    NumMibInfo: 2
+CHECK-NEXT:    NumStackOffsets: 2
+CHECK-NEXT:  Records:
+CHECK-NEXT:  -
+CHECK-NEXT:    Callstack:
+CHECK-NEXT:    -
+CHECK-NEXT:      Function: 15505678318020221912
+CHECK-NEXT:      LineOffset: 1
+CHECK-NEXT:      Column: 15
+CHECK-NEXT:      Inline: 0
+CHECK-NEXT:    -
+CHECK-NEXT:      Function: 6699318081062747564
+CHECK-NEXT:      LineOffset: 0
+CHECK-NEXT:      Column: 18
+CHECK-NEXT:      Inline: 1
+CHECK-NEXT:    -
+CHECK-NEXT:      Function: 16434608426314478903
+CHECK-NEXT:      LineOffset: 0
+CHECK-NEXT:      Column: 19
+CHECK-NEXT:      Inline: 0
+CHECK-NEXT:    -
+CHECK-NEXT:      Function: 15822663052811949562
+CHECK-NEXT:      LineOffset: 1
+CHECK-NEXT:      Column: 3
+CHECK-NEXT:      Inline: 0
+CHECK-NEXT:    MemInfoBlock:
+CHECK-NEXT:      AllocCount: 1
+CHECK-NEXT:      TotalAccessCount: 1
+CHECK-NEXT:      MinAccessCount: 1
+CHECK-NEXT:      MaxAccessCount: 1
+CHECK-NEXT:      TotalSize: 1
+CHECK-NEXT:      MinSize: 1
+CHECK-NEXT:      MaxSize: 1
+CHECK-NEXT:      AllocTimestamp: 894
+CHECK-NEXT:      DeallocTimestamp: 894
+CHECK-NEXT:      TotalLifetime: 0
+CHECK-NEXT:      MinLifetime: 0
+CHECK-NEXT:      MaxLifetime: 0
+CHECK-NEXT:      AllocCpuId: 23
+CHECK-NEXT:      DeallocCpuId: 23
+CHECK-NEXT:      NumMigratedCpu: 0
+CHECK-NEXT:      NumLifetimeOverlaps: 0
+CHECK-NEXT:      NumSameAllocCpu: 0
+CHECK-NEXT:      NumSameDeallocCpu: 0
+CHECK-NEXT:      DataTypeId: {{[0-9]+}}
+