[SYCL][ESIMD] Relax LowerESIMDSlmReservation assert (#11035)

We may end up with the basic block containing the slm_init call having
multiple predecessors, causing an assert. This pattern will not cause
any problems as the slm_init size is the same, so just skip these basic
blocks.

Signed-off-by: Sarnie, Nick <[email protected]>

Author: sarnex

llvm/lib/SYCLLowerIR/ESIMD/LowerESIMDSlmReservation.cpp

@@ -330,6 +330,14 @@ class ScopedCallGraph {
       // Do preorder traversal so that successors are visited after the parent.
       while (Wl.size() > 0) {
         BasicBlock *BB = Wl.pop_back_val();
+
+        // If we have already visited this BB but it
+        // made it into the worklist, that means this BB
+        // has multiple predecessors. We already processed the first one
+        // so just skip it.
+        if (Visited.contains(BB))
+          continue;
+
         Visited.insert(BB);
 
         for (Instruction &I : *BB) {

llvm/test/SYCLLowerIR/ESIMD/slm_init_same_bb.ll

@@ -0,0 +1,49 @@
+; This test confirms we don't assert for a single slm_init call
+; in a basic block with two predecessors.
+;
+; RUN: opt < %s -passes=LowerESIMD -S | 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"
+
+@__spirv_BuiltInGlobalInvocationId = external dso_local local_unnamed_addr addrspace(1) constant <3 x i64>, align 32
+
+; Function Attrs: convergent nounwind
+declare dso_local spir_func void @_Z16__esimd_slm_initj(i32 noundef) local_unnamed_addr
+
+; Function Attrs: nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: readwrite)
+declare void @llvm.assume(i1 noundef)
+
+; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) 
+
+; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture)
+
+; Function Attrs: convergent norecurse nounwind
+define weak_odr dso_local spir_kernel void @foo() local_unnamed_addr #0 !sycl_explicit_simd !0  {
+entry:
+  %x.i = alloca i32, align 4
+  %0 = load i64, ptr addrspace(1) @__spirv_BuiltInGlobalInvocationId, align 32
+  %cmp.i.i = icmp ult i64 %0, 2147483648
+  tail call void @llvm.assume(i1 %cmp.i.i)
+  %tobool.not.i = icmp eq i64 %0, 0
+  br i1 %tobool.not.i, label %foo.exit, label %if.then.i
+
+if.then.i:                                        ; preds = %entry
+  call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %x.i)
+  %1 = addrspacecast ptr %x.i to ptr addrspace(4)
+  store volatile i32 0, ptr addrspace(4) %1, align 4
+  call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %x.i)
+  br label %foo.exit
+
+; CHECK: foo.exit:
+; CHECK-NEXT: ret void
+foo.exit: ; preds = %entry, %if.then.i
+  tail call spir_func void @_Z16__esimd_slm_initj(i32 noundef 100) #4
+  ret void
+}
+
+attributes #0 = { convergent norecurse nounwind "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "sycl-module-id"="test.cpp" "sycl-optlevel"="2" "uniform-work-group-size"="true" }
+
+!0 = !{}