[PGO] Check that PGOOpt exists before using PGOOpt->ColdOptType (#89139)

This means that the pass is unusable without some sort of profile. We
can revisit this decision later if we want to support running this pass
without a profile.

Author: aeubanks

llvm/lib/Passes/PassBuilderPipelines.cpp

@@ -1169,7 +1169,7 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
   if (EnableSyntheticCounts && !PGOOpt)
     MPM.addPass(SyntheticCountsPropagation());
 
-  if (EnablePGOForceFunctionAttrs)
+  if (EnablePGOForceFunctionAttrs && PGOOpt)
     MPM.addPass(PGOForceFunctionAttrsPass(PGOOpt->ColdOptType));
 
   MPM.addPass(AlwaysInlinerPass(/*InsertLifetimeIntrinsics=*/true));

llvm/test/Instrumentation/PGOForceFunctionAttrs/basic.ll

@@ -5,6 +5,7 @@
 
 ; Should be no changes without profile data
 ; RUN: opt < %s -passes=pgo-force-function-attrs                                  -S -pgo-cold-func-opt=minsize | FileCheck %s --check-prefixes=NONE,CHECK
+; RUN: opt < %s -passes='default<O2>' -enable-pgo-force-function-attrs            -S -pgo-cold-func-opt=minsize | FileCheck %s --check-prefixes=O2
 
 ; NONE-NOT: Function Attrs:
 ; OPTSIZE: Function Attrs: optsize{{$}}
@@ -37,6 +38,9 @@
 ; CHECK-NOT: Function Attrs: {{.*}}minsize
 ; CHECK-NOT: Function Attrs: {{.*}}optnone
 
+; O2: define void @cold_attr(){{.*}} #[[ATTR:[0-9]+]]
+; O2-NOT: #[[ATTR]] = {{.*}}minsize
+
 @s = global i32 0
 
 define void @cold() !prof !27 {