[sycl-post-link] Do not treat declarations as entry points (#4927)

If declaration is treated as entry point, then we will create a
device image which claims that it contains particular kernel,
while it actually doesn't - that leads to errors at runtime.

Kernel declarations can appear in input modules as a side
effect of #4409. The PR postponed removal of
`@llvm.used` variable from input modules, which results
in kernel declarations left in modules after split between
SYCL and ESIMD kernels.

Author: AlexeySachkov

llvm/test/tools/sycl-post-link/split-with-kernel-declarations.ll

@@ -0,0 +1,74 @@
+; Purpose of this test is to check that sycl-post-link does not treat
+; declarations as entry points.
+
+; RUN: sycl-post-link -split=source -symbols -S %s -o %t.table
+; RUN: FileCheck %s -input-file=%t.table --check-prefix CHECK-PER-SOURCE-TABLE
+; RUN: FileCheck %s -input-file=%t_0.sym --check-prefix CHECK-PER-SOURCE-SYM0
+; RUN: FileCheck %s -input-file=%t_1.sym --check-prefix CHECK-PER-SOURCE-SYM1
+;
+; RUN: sycl-post-link -split=kernel -symbols -S %s -o %t1.table
+; RUN: FileCheck %s -input-file=%t1.table --check-prefix CHECK-PER-KERNEL-TABLE
+; RUN: FileCheck %s -input-file=%t1_0.sym --check-prefix CHECK-PER-KERNEL-SYM0
+; RUN: FileCheck %s -input-file=%t1_1.sym --check-prefix CHECK-PER-KERNEL-SYM1
+; RUN: FileCheck %s -input-file=%t1_2.sym --check-prefix CHECK-PER-KERNEL-SYM2
+
+; With per-source split, there should be two device images
+; CHECK-PER-SOURCE-TABLE: [Code|Properties|Symbols]
+; CHECK-PER-SOURCE-TABLE: {{.*}}_0.ll|{{.*}}_0.prop|{{.*}}_0.sym
+; CHECK-PER-SOURCE-TABLE-NEXT: {{.*}}_1.ll|{{.*}}_1.prop|{{.*}}_1.sym
+; CHECK-PER-SOURCE-TABLE-EMPTY:
+;
+; CHECK-PER-SOURCE-SYM0-NOT: _ZTS4mainE10TU1_kernel1
+; CHECK-PER-SOURCE-SYM0: _ZTSZ4mainE11TU0_kernel0
+; CHECK-PER-SOURCE-SYM0-NEXT: _ZTSZ4mainE11TU0_kernel1
+; CHECK-PER-SOURCE-SYM0-EMPTY:
+;
+; CHECK-PER-SOURCE-SYM1-NOT: _ZTS4mainE10TU1_kernel1
+; CHECK-PER-SOURCE-SYM1: _ZTSZ4mainE10TU1_kernel0
+; CHECK-PER-SOURCE-SYM1-EMPTY:
+
+; With per-kernel split, there should be three device images
+; CHECK-PER-KERNEL-TABLE: [Code|Properties|Symbols]
+; CHECK-PER-KERNEL-TABLE: {{.*}}_0.ll|{{.*}}_0.prop|{{.*}}_0.sym
+; CHECK-PER-KERNEL-TABLE-NEXT: {{.*}}_1.ll|{{.*}}_1.prop|{{.*}}_1.sym
+; CHECK-PER-KERNEL-TABLE-NEXT: {{.*}}_2.ll|{{.*}}_2.prop|{{.*}}_2.sym
+; CHECK-PER-KERNEL-TABLE-EMPTY:
+;
+; CHECK-PER-KERNEL-SYM0-NOT: _ZTS4mainE10TU1_kernel1
+; CHECK-PER-KERNEL-SYM0: _ZTSZ4mainE10TU1_kernel0
+; CHECK-PER-KERNEL-SYM0-EMPTY:
+;
+; CHECK-PER-KERNEL-SYM1-NOT: _ZTS4mainE10TU1_kernel1
+; CHECK-PER-KERNEL-SYM1: _ZTSZ4mainE11TU0_kernel0
+; CHECK-PER-KERNEL-SYM1-EMPTY:
+;
+; CHECK-PER-KERNEL-SYM2-NOT: _ZTS4mainE10TU1_kernel1
+; CHECK-PER-KERNEL-SYM2: _ZTSZ4mainE11TU0_kernel1
+; CHECK-PER-KERNEL-SYM2-EMPTY:
+
+target datalayout = "e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024"
+target triple = "spir64-unknown-linux"
+
+define spir_kernel void @_ZTSZ4mainE11TU0_kernel0() #0 {
+entry:
+  ret void
+}
+
+define spir_kernel void @_ZTSZ4mainE11TU0_kernel1() #0 {
+entry:
+  ret void
+}
+
+define spir_kernel void @_ZTSZ4mainE10TU1_kernel0() #1 {
+  ret void
+}
+
+declare spir_kernel void @_ZTS4mainE10TU1_kernel1() #1
+
+attributes #0 = { "sycl-module-id"="TU1.cpp" }
+attributes #1 = { "sycl-module-id"="TU2.cpp" }
+
+!opencl.spir.version = !{!0, !0}
+!spirv.Source = !{!1, !1}
+!0 = !{i32 1, i32 2}
+!1 = !{i32 4, i32 100000}

llvm/tools/sycl-post-link/sycl-post-link.cpp

@@ -288,6 +288,11 @@ bool isSpirvSyclBuiltin(StringRef FName) {
 }
 
 bool isEntryPoint(const Function &F) {
+  // Skip declarations, if any: they should not be included into KernelModuleMap
+  // or otherwise we will end up with incorrectly generated list of symbols.
+  if (F.isDeclaration())
+    return false;
+
   // Kernels are always considered to be entry points
   if (CallingConv::SPIR_KERNEL == F.getCallingConv())
     return true;