[Inline] Copy "null-pointer-is-valid" attribute in caller.

[manojgupta]

Summary

Normally, inling does not happen if caller does not have
"null-pointer-is-valid"="true" attibute but callee has it.

However, alwaysinline may force callee to be inlined.
In this case, if the caller has the "null-pointer-is-valid"="true"
attribute, copy the attribute to caller.

[lebedev.ri]

Congrats on D50000 :)

[efriedma]

LGTM

[manojgupta]

In D50000#1180760, @lebedev.ri wrote:

Congrats on D50000 :)

🎉🎉🎉

include/llvm/IR/Attributes.td

 def : MergeRule<"setAND<UnsafeFPMathAttr>">;
 def : MergeRule<"setOR<NoImplicitFloatAttr>">;
 def : MergeRule<"setOR<NoJumpTablesAttr>">;
 def : MergeRule<"setOR<ProfileSampleAccurateAttr>">;
 def : MergeRule<"adjustCallerSSPLevel">;
 def : MergeRule<"adjustCallerStackProbes">;
 def : MergeRule<"adjustCallerStackProbeSize">;
 def : MergeRule<"adjustMinLegalVectorWidth">;
+def : MergeRule<"adjustNullPointerValidAttr">;

lib/IR/Attributes.cpp

if (Caller.hasFnAttribute("min-legal-vector-width")) {
         Caller.addFnAttr(Callee.getFnAttribute("min-legal-vector-width"));
       }
     } else {
       Caller.addFnAttr(Callee.getFnAttribute("min-legal-vector-width"));
     }
   }
 }
 
+/// If the inlined function has "null-pointer-is-valid=true" attribute,
+/// set this attribute in the caller post inlining.
+static void
+adjustNullPointerValidAttr(Function &Caller, const Function &Callee) {
+  if (Callee.nullPointerIsDefined() && !Caller.nullPointerIsDefined()) {
+    Caller.addFnAttr(Callee.getFnAttribute("null-pointer-is-valid"));
+  }
+}
+
+
 #define GET_ATTR_COMPAT_FUNC
 #include "AttributesCompatFunc.inc"
 
 bool AttributeFuncs::areInlineCompatible(const Function &Caller,
                                          const Function &Callee) {
   return hasCompatibleFnAttrs(Caller, Callee);
 }
 
 void AttributeFuncs::mergeAttributesForInlining(Function &Caller,
                                                 const Function &Callee) {
   mergeFnAttrs(Caller, Callee);
 }

test/Transforms/Inline/attributes.ll

 
 define i32 @test_no-use-jump-tables3(i32 %i) "no-jump-tables"="true" {
   %1 = call i32 @no-use-jump-tables_callee1(i32 %i)
   ret i32 %1
 ; CHECK: @test_no-use-jump-tables3(i32 %i) [[NOUSEJUMPTABLES]] {
 ; CHECK-NEXT: ret i32
 }
 
-; Calle with "null-pointer-is-valid"="true" attribute should not be inlined
-; into a caller without this attribute. Exception: alwaysinline callee
-; can still be inlined.
+; Callee with "null-pointer-is-valid"="true" attribute should not be inlined
+; into a caller without this attribute.
+; Exception: alwaysinline callee can still be inlined but
+; "null-pointer-is-valid"="true" should get copied to caller.
 
 define i32 @null-pointer-is-valid_callee0(i32 %i) "null-pointer-is-valid"="true" {
   ret i32 %i
 ; CHECK: @null-pointer-is-valid_callee0(i32 %i)
 ; CHECK-NEXT: ret i32
 }
 
 define i32 @null-pointer-is-valid_callee1(i32 %i) alwaysinline "null-pointer-is-valid"="true" {
   ret i32 %i
 ; CHECK: @null-pointer-is-valid_callee1(i32 %i)
 ; CHECK-NEXT: ret i32
 }
 
 define i32 @null-pointer-is-valid_callee2(i32 %i)  {
   ret i32 %i
 ; CHECK: @null-pointer-is-valid_callee2(i32 %i)
 ; CHECK-NEXT: ret i32
 }
 
+; No inlining since caller does not have "null-pointer-is-valid"="true" attribute.
 define i32 @test_null-pointer-is-valid0(i32 %i) {
   %1 = call i32 @null-pointer-is-valid_callee0(i32 %i)
   ret i32 %1
 ; CHECK: @test_null-pointer-is-valid0(
 ; CHECK: call i32 @null-pointer-is-valid_callee0
 ; CHECK-NEXT: ret i32
 }
 
-define i32 @test_null-pointer-is-valid1(i32 %i) {
+; alwaysinline should force inlining even when caller does not have
+; "null-pointer-is-valid"="true" attribute. However, the attribute should be
+; copied to caller.
+define i32 @test_null-pointer-is-valid1(i32 %i) "null-pointer-is-valid"="false" {
   %1 = call i32 @null-pointer-is-valid_callee1(i32 %i)
   ret i32 %1
-; CHECK: @test_null-pointer-is-valid1(
+; CHECK: @test_null-pointer-is-valid1(i32 %i) [[NULLPOINTERISVALID:#[0-9]+]] {
 ; CHECK-NEXT: ret i32
 }
 
+; Can inline since both caller and callee have "null-pointer-is-valid"="true"
+; attribute.
 define i32 @test_null-pointer-is-valid2(i32 %i) "null-pointer-is-valid"="true" {
   %1 = call i32 @null-pointer-is-valid_callee2(i32 %i)
   ret i32 %1
-; CHECK: @test_null-pointer-is-valid2(
+; CHECK: @test_null-pointer-is-valid2(i32 %i) [[NULLPOINTERISVALID]] {
 ; CHECK-NEXT: ret i32
 }
 
 ; CHECK: attributes [[FPMAD_FALSE]] = { "less-precise-fpmad"="false" }
 ; CHECK: attributes [[FPMAD_TRUE]] = { "less-precise-fpmad"="true" }
 ; CHECK: attributes [[NOIMPLICITFLOAT]] = { noimplicitfloat }
 ; CHECK: attributes [[NOUSEJUMPTABLES]] = { "no-jump-tables"="true" }
+; CHECK: attributes [[NULLPOINTERISVALID]] = { "null-pointer-is-valid"="true" }