[ESIMD] ESIMDOptimizeVecArgCallConv: allow more IR patterns. (#6919)

Allow all-zero GEPs in optimized ptr param use-def chains.

Signed-off-by: Konstantin S Bobrovsky <konstantin.s.bobrovsky@intel.com>

llvm/include/llvm/SYCLLowerIR/ESIMD/ESIMDUtils.h

@@ -68,16 +68,34 @@ inline void assert_and_diag(bool Condition, StringRef Msg,
 /// Tells if this value is a bit cast or address space cast.
 bool isCast(const Value *V);
 
+/// Tells if this value is a GEP instructions with all zero indices.
+bool isZeroGEP(const Value *V);
+
 /// Climbs up the use-def chain of given value until a value which is not a
 /// bit cast or address space cast is met.
 const Value *stripCasts(const Value *V);
 Value *stripCasts(Value *V);
 
+/// Climbs up the use-def chain of given value until a value is met which is
+/// neither of:
+/// - bit cast
+/// - address space cast
+/// - GEP instruction with all zero indices
+const Value *stripCastsAndZeroGEPs(const Value *V);
+Value *stripCastsAndZeroGEPs(Value *V);
+
 /// Collects uses of given value "looking through" casts. I.e. if a use is a
 /// cast (chain), then uses of the result of the cast (chain) are collected.
 void collectUsesLookThroughCasts(const Value *V,
                                  SmallPtrSetImpl<const Use *> &Uses);
 
+/// Collects uses of given pointer-typed value "looking through" casts and GEPs
+/// with all zero indices - those pointer transformation instructions which
+/// don't change pointed-to value. E.g. if a use is a cast (chain), then uses of
+/// the result of the cast (chain) are collected.
+void collectUsesLookThroughCastsAndZeroGEPs(const Value *V,
+                                            SmallPtrSetImpl<const Use *> &Uses);
+
 /// Unwraps a presumably simd* type to extract the native vector type encoded
 /// in it. Returns nullptr if failed to do so.
 Type *getVectorTyOrNull(StructType *STy);

llvm/lib/SYCLLowerIR/ESIMD/ESIMDOptimizeVecArgCallConv.cpp

@@ -76,7 +76,7 @@ getMemTypeIfSameAddressLoadsStores(SmallPtrSetImpl<const Use *> &Uses,
   if (Uses.size() == 0) {
     return nullptr;
   }
-  Value *Addr = esimd::stripCasts((*Uses.begin())->get());
+  Value *Addr = esimd::stripCastsAndZeroGEPs((*Uses.begin())->get());
 
   for (const auto *UU : Uses) {
     const User *U = UU->getUser();
@@ -92,7 +92,7 @@ getMemTypeIfSameAddressLoadsStores(SmallPtrSetImpl<const Use *> &Uses,
     }
 
     if (const auto *SI = dyn_cast<StoreInst>(U)) {
-      if (esimd::stripCasts(SI->getPointerOperand()) != Addr) {
+      if (esimd::stripCastsAndZeroGEPs(SI->getPointerOperand()) != Addr) {
         // the pointer escapes into memory
         return nullptr;
       }
@@ -167,7 +167,7 @@ Type *getPointedToTypeIfOptimizeable(const Argument &FormalParam) {
   //   }
   {
     SmallPtrSet<const Use *, 4> Uses;
-    esimd::collectUsesLookThroughCasts(&FormalParam, Uses);
+    esimd::collectUsesLookThroughCastsAndZeroGEPs(&FormalParam, Uses);
     bool LoadMet = 0;
     bool StoreMet = 0;
     ContentT = getMemTypeIfSameAddressLoadsStores(Uses, LoadMet, StoreMet);
@@ -225,14 +225,14 @@ Type *getPointedToTypeIfOptimizeable(const Argument &FormalParam) {
     if (!Call || (Call->getCalledFunction() != F)) {
       return nullptr;
     }
-    auto ArgNo = FormalParam.getArgNo();
-    Value *ActualParam = esimd::stripCasts(Call->getArgOperand(ArgNo));
+    Value *ActualParam = esimd::stripCastsAndZeroGEPs(
+        Call->getArgOperand(FormalParam.getArgNo()));
 
     if (!IsSret && !isa<AllocaInst>(ActualParam)) {
       return nullptr;
     }
     SmallPtrSet<const Use *, 4> Uses;
-    esimd::collectUsesLookThroughCasts(ActualParam, Uses);
+    esimd::collectUsesLookThroughCastsAndZeroGEPs(ActualParam, Uses);
     bool LoadMet = 0;
     bool StoreMet = 0;
 

llvm/lib/SYCLLowerIR/ESIMD/ESIMDUtils.cpp

@@ -89,6 +89,11 @@ bool isCast(const Value *V) {
   return (Opc == Instruction::BitCast) || (Opc == Instruction::AddrSpaceCast);
 }
 
+bool isZeroGEP(const Value *V) {
+  const auto *GEPI = dyn_cast<GetElementPtrInst>(V);
+  return GEPI && GEPI->hasAllZeroIndices();
+}
+
 const Value *stripCasts(const Value *V) {
   if (!V->getType()->isPtrOrPtrVectorTy())
     return V;
@@ -110,6 +115,30 @@ Value *stripCasts(Value *V) {
   return const_cast<Value *>(stripCasts(const_cast<const Value *>(V)));
 }
 
+const Value *stripCastsAndZeroGEPs(const Value *V) {
+  if (!V->getType()->isPtrOrPtrVectorTy())
+    return V;
+  // Even though we don't look through PHI nodes, we could be called on an
+  // instruction in an unreachable block, which may be on a cycle.
+  SmallPtrSet<const Value *, 4> Visited;
+  Visited.insert(V);
+
+  do {
+    if (isCast(V)) {
+      V = cast<Operator>(V)->getOperand(0);
+    } else if (isZeroGEP(V)) {
+      V = cast<GetElementPtrInst>(V)->getOperand(0);
+    }
+    assert(V->getType()->isPtrOrPtrVectorTy() && "Unexpected operand type!");
+  } while (Visited.insert(V).second);
+  return V;
+}
+
+Value *stripCastsAndZeroGEPs(Value *V) {
+  return const_cast<Value *>(
+      stripCastsAndZeroGEPs(const_cast<const Value *>(V)));
+}
+
 void collectUsesLookThroughCasts(const Value *V,
                                  SmallPtrSetImpl<const Use *> &Uses) {
   for (const Use &U : V->uses()) {
@@ -123,6 +152,21 @@ void collectUsesLookThroughCasts(const Value *V,
   }
 }
 
+void collectUsesLookThroughCastsAndZeroGEPs(
+    const Value *V, SmallPtrSetImpl<const Use *> &Uses) {
+  assert(V->getType()->isPtrOrPtrVectorTy() && "pointer type expected");
+
+  for (const Use &U : V->uses()) {
+    Value *VV = U.getUser();
+
+    if (isCast(VV) || isZeroGEP(VV)) {
+      collectUsesLookThroughCastsAndZeroGEPs(VV, Uses);
+    } else {
+      Uses.insert(&U);
+    }
+  }
+}
+
 Type *getVectorTyOrNull(StructType *STy) {
   Type *Res = nullptr;
   while (STy && (STy->getStructNumElements() == 1)) {

llvm/test/SYCLLowerIR/ESIMD/vec_arg_call_conv.ll

@@ -255,6 +255,38 @@ entry:
   ret void
 }
 
+;----- Test4: IR contains all-zero GEP instructions in parameter use-def chains
+; Based on Test2.
+define dso_local spir_func void @_Z23callee__sret__x_param_x1(ptr addrspace(4) noalias sret(%"class.sycl::_V1::ext::intel::esimd::simd.2") align 32 %agg.result, i32 noundef %i, ptr noundef %x, i32 noundef %j) local_unnamed_addr #3 !sycl_explicit_simd !8 !intel_reqd_sub_group_size !9 {
+; CHECK: define dso_local spir_func <8 x i32> @_Z23callee__sret__x_param_x1(i32 noundef %{{.*}}, <8 x i32> %{{.*}}, i32 noundef %{{.*}})
+entry:
+  %x.ascast = addrspacecast ptr %x to ptr addrspace(4)
+  %add = add nsw i32 %i, %j
+  %splat.splatinsert.i.i.i = insertelement <8 x i32> poison, i32 %add, i64 0
+  %splat.splat.i.i.i = shufflevector <8 x i32> %splat.splatinsert.i.i.i, <8 x i32> poison, <8 x i32> zeroinitializer
+  %M_data.i.i.i = getelementptr inbounds %"class.sycl::_V1::ext::intel::esimd::detail::simd_obj_impl.3", ptr addrspace(4) %x.ascast, i64 0, i32 0
+  %call.i.i.i1 = load <8 x i32>, ptr addrspace(4) %M_data.i.i.i, align 32
+  %add.i.i.i.i.i = add <8 x i32> %call.i.i.i1, %splat.splat.i.i.i
+  store <8 x i32> %add.i.i.i.i.i, ptr addrspace(4) %agg.result, align 32
+  ret void
+}
+
+;----- Test4 caller.
+; Function Attrs: convergent noinline norecurse
+define dso_local spir_func void @_Z21test__sret__x_param_x1(ptr addrspace(4) noalias sret(%"class.sycl::_V1::ext::intel::esimd::simd.2") align 32 %agg.result, ptr noundef %x) local_unnamed_addr #3 !sycl_explicit_simd !8 !intel_reqd_sub_group_size !9 {
+; CHECK: define dso_local spir_func <8 x i32> @_Z21test__sret__x_param_x1(<8 x i32> %{{.*}})
+entry:
+  %agg.tmp = alloca %"class.sycl::_V1::ext::intel::esimd::simd.2", align 32
+  %agg.tmp.ascast = addrspacecast ptr %agg.tmp to ptr addrspace(4)
+  %x.ascast = addrspacecast ptr %x to ptr addrspace(4)
+  %M_data.i.i.i = getelementptr inbounds %"class.sycl::_V1::ext::intel::esimd::detail::simd_obj_impl.3", ptr addrspace(4) %x.ascast, i64 0, i32 0
+  %call.i.i.i1 = load <8 x i32>, ptr addrspace(4) %M_data.i.i.i, align 32
+  store <8 x i32> %call.i.i.i1, ptr addrspace(4) %agg.tmp.ascast, align 32
+  call spir_func void @_Z23callee__sret__x_param_x1(ptr addrspace(4) sret(%"class.sycl::_V1::ext::intel::esimd::simd.2") align 32 %agg.result, i32 noundef 2, ptr noundef nonnull %agg.tmp, i32 noundef 1) #7
+; CHECK:  %{{.*}} = call spir_func <8 x i32> @_Z23callee__sret__x_param_x1(i32 2, <8 x i32> %{{.*}}, i32 1)
+  ret void
+}
+
 attributes #0 = { convergent noinline norecurse "frame-pointer"="all" "min-legal-vector-width"="512" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "sycl-module-id"="../opaque_ptr.cpp" }
 attributes #1 = { alwaysinline convergent "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
 attributes #2 = { convergent noinline norecurse "frame-pointer"="all" "min-legal-vector-width"="12288" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "sycl-module-id"="../opaque_ptr.cpp" }