diff --git a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
--- a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
@@ -1422,6 +1422,11 @@
     Align AlignCandidate = getFunctionParamOptimizedAlign(F, ETy, DL);
     ParamByValAlign = std::max(ParamByValAlign, AlignCandidate);
 
+    // Enforce minumum alignment of 4 to work around ptxas miscompile
+    // for sm_50+. See corresponding alignment adjustment in
+    // emitFunctionParamList() for details.
+    ParamByValAlign = std::max(ParamByValAlign, Align(4));
+
     O << ".param .align " << ParamByValAlign.value() << " .b8 ";
     O << "_";
     O << "[" << Outs[OIdx].Flags.getByValSize() << "]";
diff --git a/llvm/test/CodeGen/NVPTX/call_bitcast_byval.ll b/llvm/test/CodeGen/NVPTX/call_bitcast_byval.ll
--- a/llvm/test/CodeGen/NVPTX/call_bitcast_byval.ll
+++ b/llvm/test/CodeGen/NVPTX/call_bitcast_byval.ll
@@ -37,9 +37,9 @@
   %fp = call ptr @usefp(ptr @callee)
   ; CHECK: .param .align 4 .b8 param0[4];
   ; CHECK: st.param.v2.b16 [param0+0]
-  ; CHECK: .callprototype ()_ (.param .align 2 .b8 _[4]);
+  ; CHECK: .callprototype ()_ (.param .align 4 .b8 _[4]);
   call void %fp(ptr byval(%"class.complex") null)
   ret void
 }
 
-declare %complex_half @_Z20__spirv_GroupCMulKHRjjN5__spv12complex_halfE()
+declare %complex_half @_Z20__spirv_GroupCMulKHRjjN5__spv12complex_halfE(i32, i32, ptr byval(%"class.complex"))
diff --git a/llvm/test/CodeGen/NVPTX/param-align.ll b/llvm/test/CodeGen/NVPTX/param-align.ll
--- a/llvm/test/CodeGen/NVPTX/param-align.ll
+++ b/llvm/test/CodeGen/NVPTX/param-align.ll
@@ -43,3 +43,24 @@
   call void @t4(ptr byval(i8) %x)
   ret void
 }
+
+;;; Make sure we adjust alignment for a function prototype
+;;; in case of an inderec call.
+
+declare ptr @getfp(i32 %n)
+%struct.half2 = type { half, half }
+define ptx_device void @t6() {
+; CHECK: .func t6
+  %fp = call ptr @getfp(i32 0)
+; CHECK: prototype_2 : .callprototype ()_ (.param .align 8 .b8 _[8]);
+  call void %fp(ptr byval(double) null);
+
+  %fp2 = call ptr @getfp(i32 1)
+; CHECK: prototype_4 : .callprototype ()_ (.param .align 4 .b8 _[4]);
+  call void %fp(ptr byval(%struct.half2) null);
+
+  %fp3 = call ptr @getfp(i32 2)
+; CHECK: prototype_6 : .callprototype ()_ (.param .align 4 .b8 _[1]);
+  call void %fp(ptr byval(i8) null);
+  ret void
+}