[PATCH] D135708: [NVPTX] Fix alignment for arguments of function pointer calls

[Andrew Savonichev via Phabricator via llvm-commits]

asavonic created this revision.
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Alignment of function arguments can be increased only if we can do
this for all call sites. Therefore we do not increase it for external
functions, and now we skip functions that have address taken, to avoid
any issues with functions pointers.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D135708

Files:
  llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
  llvm/test/CodeGen/NVPTX/call_bitcast_byval.ll


Index: llvm/test/CodeGen/NVPTX/call_bitcast_byval.ll
===================================================================
--- llvm/test/CodeGen/NVPTX/call_bitcast_byval.ll
+++ llvm/test/CodeGen/NVPTX/call_bitcast_byval.ll
@@ -13,16 +13,34 @@
 %"class.sycl::_V1::detail::half_impl::half" = type { half }
 %complex_half = type { half, half }
 
+; CHECK: .param .align 4 .b8 param2[4];
+; CHECK: st.param.v2.b16         [param2+0], {%h2, %h1};
+; CHECK: .param .align 2 .b8 retval0[4];
+; CHECK: call.uni (retval0),
+; CHECK-NEXT: _Z20__spirv_GroupCMulKHRjjN5__spv12complex_halfE,
 define weak_odr void @foo() {
 entry:
   %call.i.i.i = tail call %"class.complex" bitcast (%complex_half ()* @_Z20__spirv_GroupCMulKHRjjN5__spv12complex_halfE to %"class.complex" (i32, i32, %"class.complex"*)*)(i32 0, i32 0, %"class.complex"* byval(%"class.complex") null)
   ret void
 }
 
-declare %complex_half @_Z20__spirv_GroupCMulKHRjjN5__spv12complex_halfE()
+;; Function pointers can escape, so we have to use a conservative
+;; alignment for a function that has address taken.
+;;
+declare i8* @usefp(i8* %fp)
+; CHECK: .func callee(
+; CHECK-NEXT: .param .align 4 .b8 callee_param_0[4]
+define internal void @callee(%"class.complex"* byval(%"class.complex") %byval_arg) {
+  ret void
+}
+define void @boom() {
+  %fp = call i8* @usefp(i8* bitcast (void (%"class.complex"*)* @callee to i8*))
+  %cast = bitcast i8* %fp to void (%"class.complex"*)*
+  ; CHECK: .param .align 4 .b8 param0[4];
+  ; CHECK: st.param.v2.b16 [param0+0]
+  ; CHECK: .callprototype ()_ (.param .align 2 .b8 _[4]);
+  call void %cast(%"class.complex"* byval(%"class.complex") null)
+  ret void
+}
 
-; CHECK: .param .align 4 .b8 param2[4];
-; CHECK: st.param.v2.b16         [param2+0], {%h2, %h1};
-; CHECK: .param .align 2 .b8 retval0[4];
-; CHECK: call.uni (retval0),
-; CHECK-NEXT: _Z20__spirv_GroupCMulKHRjjN5__spv12complex_halfE,
+declare %complex_half @_Z20__spirv_GroupCMulKHRjjN5__spv12complex_halfE()
Index: llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
===================================================================
--- llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
+++ llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
@@ -4326,8 +4326,13 @@
   const uint64_t ABITypeAlign = DL.getABITypeAlign(ArgTy).value();
 
   // If a function has linkage different from internal or private, we
-  // must use default ABI alignment as external users rely on it.
-  if (!(F && F->hasLocalLinkage()))
+  // must use default ABI alignment as external users rely on it. Same
+  // for a function that may be called from a function pointer.
+  if (!F || !F->hasLocalLinkage()) ||
+      F->hasAddressTaken(/*Users=*/nullptr,
+                         /*IgnoreCallbackUses=*/false,
+                         /*IgnoreAssumeLikeCalls=*/true,
+                         /*IngoreLLVMUsed=*/true))
     return Align(ABITypeAlign);
 
   assert(!isKernelFunction(*F) && "Expect kernels to have non-local linkage");


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