[SYCL] Do not crash if no matching store found in SYCLMutatePrintfAddrspacePass (#15658)

In SYCLMutatePrintfAddrspacePass, when analyzing a format pointer to
printf, do not crash when analyzing backwards through load/stores if no
matching store is found.

---------

Signed-off-by: Lu, John <[email protected]>

Author: LU-JOHN

llvm/lib/SYCLLowerIR/MutatePrintfAddrspace.cpp

@@ -160,9 +160,12 @@ Value *stripToMemorySource(Value *V) {
   Value *MemoryAccess = V;
   if (auto *LI = dyn_cast<LoadInst>(MemoryAccess)) {
     Value *LoadSource = LI->getPointerOperand();
-    auto *Store = cast<StoreInst>(*llvm::find_if(
-        LoadSource->users(), [](User *U) { return isa<StoreInst>(U); }));
-    MemoryAccess = Store->getValueOperand();
+    auto Users = LoadSource->users();
+    auto I = llvm::find_if(Users, [](User *U) { return isa<StoreInst>(U); });
+    if (I != Users.end()) {
+      auto *Store = cast<StoreInst>(*I);
+      MemoryAccess = Store->getValueOperand();
+    }
   }
   return MemoryAccess->stripPointerCastsAndAliases();
 }

llvm/test/SYCLLowerIR/printf_addrspace/no_matching_store.ll

@@ -0,0 +1,47 @@
+;; This test is derived from generic_as_variadic_no_opt.ll.
+;; This test ensures that when SYCLMutatePrintfAddrspace analyzes a load
+;; of the format pointer for a printf, it will not crash if a
+;; corresponding store is not found.
+
+; RUN: not opt < %s -passes=SYCLMutatePrintfAddrspace -S 2>&1 | FileCheck %s
+
+target datalayout = "e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-n8:16:32:64"
+target triple = "spir64-unknown-unknown"
+
+$_ZN2cl4sycl3ext6oneapi12experimental6printfIcJfEEEiPKT_DpT0_ = comdat any
+
+; CHECK: error: experimental::printf requires format string to reside in constant address space. The compiler wasn't able to automatically convert your format string into constant address space when processing builtin _Z18__spirv_ocl_printf{{.*}} called in function {{.*}}.
+
+; Function Attrs: convergent mustprogress noinline norecurse optnone
+define linkonce_odr dso_local spir_func i32 @_ZN2cl4sycl3ext6oneapi12experimental6printfIcJfEEEiPKT_DpT0_(ptr addrspace(4) %__format, float %args) #2 comdat {
+entry:
+  %retval = alloca i32, align 4
+  %__format.addr = alloca ptr addrspace(4), align 8
+  %args.addr = alloca float, align 4
+  %retval.ascast = addrspacecast ptr %retval to ptr addrspace(4)
+  %__format.addr.ascast = addrspacecast ptr %__format.addr to ptr addrspace(4)
+  %args.addr.ascast = addrspacecast ptr %args.addr to ptr addrspace(4)
+;  Remove store to ensure SYCLMutatePrintfAddrspace will not crash.
+;  store ptr addrspace(4) %__format, ptr addrspace(4) %__format.addr.ascast, align 8
+  store float %args, ptr addrspace(4) %args.addr.ascast, align 4  
+  %0 = load ptr addrspace(4), ptr addrspace(4) %__format.addr.ascast, align 8
+  %1 = load float, ptr addrspace(4) %args.addr.ascast, align 4
+  %call = call spir_func i32 (ptr addrspace(4), ...) @_Z18__spirv_ocl_printfPKcz(ptr addrspace(4) %0, float %1) #8
+  ret i32 %call
+}
+
+; Function Attrs: convergent
+declare dso_local spir_func i32 @_Z18__spirv_ocl_printfPKcz(ptr addrspace(4), ...) #7
+
+attributes #2 = { convergent mustprogress noinline norecurse optnone "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+attributes #7 = { convergent "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+attributes #8 = { convergent }
+
+!llvm.module.flags = !{!0, !1}
+!opencl.spir.version = !{!2}
+!spirv.Source = !{!3}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 7, !"frame-pointer", i32 2}
+!2 = !{i32 1, i32 2}
+!3 = !{i32 4, i32 100000}