[SamplePGO] Handle FS discriminators in SampleProfileMatcher (#90858)

Currently the code uses FunctionSamples::getCallSiteIdentifier which
will sometimes incorrectly guess that FSAFDO discriminators are probe
based and will convert them incorrectly.

This change doesn't affect builds which don't use FSAFDO, it only fixes
sample profile matching with FS discriminators.

The test for this is manually updated to use discriminator value 15,
which is a perfectly valid base discriminator in the FS world, but
satisfies `isPseudoProbeDiscriminator`, so
`getBaseDiscriminatorFromDiscriminator` will incorrectly extract the
probe index from it.

Note: this change only affects how the base discriminators will be
extracted when doing stale profile matching in the IR-level sample
profile loader. It doesn't add stale profile matching to the MIR-level
FS profile loader pass.

llvm/lib/Transforms/IPO/SampleProfileMatcher.cpp

@@ -37,7 +37,8 @@ void SampleProfileMatcher::findIRAnchors(
       DIL = DIL->getInlinedAt();
     } while (DIL->getInlinedAt());
 
-    LineLocation Callsite = FunctionSamples::getCallSiteIdentifier(DIL);
+    LineLocation Callsite = FunctionSamples::getCallSiteIdentifier(
+        DIL, FunctionSamples::ProfileIsFS);
     StringRef CalleeName = PrevDIL->getSubprogramLinkageName();
     return std::make_pair(Callsite, CalleeName);
   };
@@ -82,7 +83,8 @@ void SampleProfileMatcher::findIRAnchors(
         if (DIL->getInlinedAt()) {
           IRAnchors.emplace(FindTopLevelInlinedCallsite(DIL));
         } else {
-          LineLocation Callsite = FunctionSamples::getCallSiteIdentifier(DIL);
+          LineLocation Callsite = FunctionSamples::getCallSiteIdentifier(
+              DIL, FunctionSamples::ProfileIsFS);
           StringRef CalleeName = GetCanonicalCalleeName(dyn_cast<CallBase>(&I));
           IRAnchors.emplace(Callsite, CalleeName);
         }

llvm/test/Transforms/SampleProfile/Inputs/non-probe-stale-profile-matching.prof

@@ -10,12 +10,12 @@ main:9229397:0
  7: 0
  2: foo:1479916
   1: 47663
-  1.1: 46683 bar:43238
+  1.15: 46683 bar:43238
   2: 4519 bar:4932
   3: 48723
  4: foo:1505537
   1: 48604
-  1.1: 46965 bar:44479
+  1.15: 46965 bar:44479
   2: 4613 bar:4967
   3: 49087
 bar:2333388:196222

llvm/test/Transforms/SampleProfile/non-probe-stale-profile-matching.ll

@@ -1,6 +1,6 @@
 ; REQUIRES: x86_64-linux
 ; REQUIRES: asserts
-; RUN: opt < %s -passes=sample-profile -sample-profile-file=%S/Inputs/non-probe-stale-profile-matching.prof --salvage-stale-profile -S --debug-only=sample-profile,sample-profile-matcher,sample-profile-impl 2>&1 | FileCheck %s
+; RUN: opt < %s -passes=sample-profile -sample-profile-file=%S/Inputs/non-probe-stale-profile-matching.prof --salvage-stale-profile -S --debug-only=sample-profile,sample-profile-matcher,sample-profile-impl -profile-isfs 2>&1 | FileCheck %s
 
 ; The profiled source code:
 
@@ -51,7 +51,7 @@
 ; CHECK: Run stale profile matching for bar
 
 ; CHECK: Run stale profile matching for foo
-; CHECK: Callsite with callee:bar is matched from 1.1 to 1.1
+; CHECK: Callsite with callee:bar is matched from 1.15 to 1.15
 ; CHECK: Callsite with callee:bar is matched from 2 to 2
 
 ; CHECK: Run stale profile matching for main
@@ -183,7 +183,7 @@ attributes #3 = { mustprogress nocallback nofree nosync nounwind willreturn memo
 !15 = !DILocation(line: 7, column: 9, scope: !14)
 !16 = !DILocation(line: 7, column: 7, scope: !14)
 !17 = !DILocation(line: 7, column: 23, scope: !18)
-!18 = !DILexicalBlockFile(scope: !14, file: !10, discriminator: 2)
+!18 = !DILexicalBlockFile(scope: !14, file: !10, discriminator: 15)
 !19 = !DILocation(line: 7, column: 15, scope: !18)
 !20 = !DILocation(line: 8, column: 21, scope: !14)
 !21 = !DILocation(line: 8, column: 15, scope: !14)
@@ -201,7 +201,7 @@ attributes #3 = { mustprogress nocallback nofree nosync nounwind willreturn memo
 !33 = !DILocation(line: 14, column: 8, scope: !25)
 !34 = !DILocation(line: 14, scope: !25)
 !35 = !DILocation(line: 14, column: 21, scope: !36)
-!36 = !DILexicalBlockFile(scope: !25, file: !10, discriminator: 2)
+!36 = !DILexicalBlockFile(scope: !25, file: !10, discriminator: 15)
 !37 = !DILocation(line: 14, column: 3, scope: !36)
 !38 = !DILocation(line: 14, column: 3, scope: !39)
 !39 = !DILexicalBlockFile(scope: !25, file: !10, discriminator: 4)