[Attributor] AAPointerInfo should allow "harmless" uses

If a call base use will not capture a pointer we can approximate the
effects. This is important especially for readnone/only uses.

llvm/lib/Transforms/IPO/AttributorAttributes.cpp

@@ -1517,13 +1517,32 @@ struct AAPointerInfoCallSiteArgument final : AAPointerInfoFloating {
     //       sense to specialize attributes for call sites arguments instead of
     //       redirecting requests to the callee argument.
     Argument *Arg = getAssociatedArgument();
-    if (!Arg)
+    if (Arg) {
+      const IRPosition &ArgPos = IRPosition::argument(*Arg);
+      auto &ArgAA =
+          A.getAAFor<AAPointerInfo>(*this, ArgPos, DepClassTy::REQUIRED);
+      if (ArgAA.getState().isValidState())
+        return translateAndAddState(A, ArgAA, 0, *cast<CallBase>(getCtxI()),
+                                    /* FromCallee */ true);
+    }
+
+    const auto &NoCaptureAA =
+        A.getAAFor<AANoCapture>(*this, getIRPosition(), DepClassTy::OPTIONAL);
+
+    if (!NoCaptureAA.isAssumedNoCapture())
       return indicatePessimisticFixpoint();
-    const IRPosition &ArgPos = IRPosition::argument(*Arg);
-    auto &ArgAA =
-        A.getAAFor<AAPointerInfo>(*this, ArgPos, DepClassTy::REQUIRED);
-    return translateAndAddState(A, ArgAA, 0, *cast<CallBase>(getCtxI()),
-                                /* FromCallee */ true);
+
+    bool IsKnown = false;
+    if (AA::isAssumedReadNone(A, getIRPosition(), *this, IsKnown))
+      return ChangeStatus::UNCHANGED;
+    bool ReadOnly = AA::isAssumedReadOnly(A, getIRPosition(), *this, IsKnown);
+
+    ChangeStatus Changed = ChangeStatus::UNCHANGED;
+    handleAccess(A, *getCtxI(), getAssociatedValue(), nullptr,
+                 ReadOnly ? AccessKind::AK_MAY_READ
+                          : AccessKind::AK_MAY_READ_WRITE,
+                 0, Changed, nullptr, AA::OffsetAndSize::Unknown);
+    return Changed;
   }
 
   /// See AbstractAttribute::trackStatistics()

llvm/test/Transforms/Attributor/heap_to_stack_gpu.ll

@@ -407,11 +407,10 @@ define i32 @irreducible_cfg(i32 %0) {
 ; IS________OPM-NEXT:    [[TMP14]] = add nsw i32 [[DOT1]], 1
 ; IS________OPM-NEXT:    br label [[TMP8]]
 ; IS________OPM:       15:
-; IS________OPM-NEXT:    [[TMP16:%.*]] = load i32, i32* [[TMP3]], align 4
-; IS________OPM-NEXT:    [[TMP17:%.*]] = bitcast i32* [[TMP3]] to i8*
-; IS________OPM-NEXT:    call void @free(i8* nocapture noundef [[TMP17]])
-; IS________OPM-NEXT:    [[TMP18:%.*]] = load i32, i32* [[TMP3]], align 4
-; IS________OPM-NEXT:    ret i32 [[TMP18]]
+; IS________OPM-NEXT:    [[TMP16:%.*]] = bitcast i32* [[TMP3]] to i8*
+; IS________OPM-NEXT:    call void @free(i8* nocapture noundef [[TMP16]])
+; IS________OPM-NEXT:    [[TMP17:%.*]] = load i32, i32* [[TMP3]], align 4
+; IS________OPM-NEXT:    ret i32 [[TMP17]]
 ;
 ; IS________NPM-LABEL: define {{[^@]+}}@irreducible_cfg
 ; IS________NPM-SAME: (i32 [[TMP0:%.*]]) {
@@ -439,10 +438,9 @@ define i32 @irreducible_cfg(i32 %0) {
 ; IS________NPM-NEXT:    [[TMP14]] = add nsw i32 [[DOT1]], 1
 ; IS________NPM-NEXT:    br label [[TMP8]]
 ; IS________NPM:       15:
-; IS________NPM-NEXT:    [[TMP16:%.*]] = load i32, i32* [[TMP3]], align 4
 ; IS________NPM-NEXT:    call void @free(i8* nocapture noundef [[TMP2]])
-; IS________NPM-NEXT:    [[TMP17:%.*]] = load i32, i32* [[TMP3]], align 4
-; IS________NPM-NEXT:    ret i32 [[TMP17]]
+; IS________NPM-NEXT:    [[TMP16:%.*]] = load i32, i32* [[TMP3]], align 4
+; IS________NPM-NEXT:    ret i32 [[TMP16]]
 ;
   %2 = call noalias i8* @malloc(i64 4)
   %3 = bitcast i8* %2 to i32*

llvm/test/Transforms/Attributor/pointer-info.ll

@@ -21,13 +21,12 @@ define void @foo(i8* %ptr) {
 ;
 ; IS__CGSCC____: Function Attrs: nofree nosync nounwind readnone willreturn
 ; IS__CGSCC____-LABEL: define {{[^@]+}}@foo
-; IS__CGSCC____-SAME: (i8* nocapture nofree writeonly [[PTR:%.*]]) #[[ATTR0:[0-9]+]] {
+; IS__CGSCC____-SAME: (i8* nocapture nofree readnone [[PTR:%.*]]) #[[ATTR0:[0-9]+]] {
 ; IS__CGSCC____-NEXT:  entry:
 ; IS__CGSCC____-NEXT:    [[TMP0:%.*]] = alloca [[STRUCT_TEST_A:%.*]], align 8
 ; IS__CGSCC____-NEXT:    br label [[CALL_BR:%.*]]
 ; IS__CGSCC____:       call.br:
 ; IS__CGSCC____-NEXT:    [[TMP1:%.*]] = getelementptr inbounds [[STRUCT_TEST_A]], %struct.test.a* [[TMP0]], i64 0, i32 2
-; IS__CGSCC____-NEXT:    store i8* [[PTR]], i8** [[TMP1]], align 8
 ; IS__CGSCC____-NEXT:    tail call void @bar(%struct.test.a* noalias nocapture nofree noundef nonnull readnone byval([[STRUCT_TEST_A]]) align 8 dereferenceable(24) [[TMP0]]) #[[ATTR2:[0-9]+]]
 ; IS__CGSCC____-NEXT:    ret void
 ;

llvm/test/Transforms/Attributor/value-simplify-pointer-info-struct.ll

@@ -29,13 +29,15 @@ target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16
 ;
 @GlobalS = internal constant %struct.S { i32 42, double 3.140000e+00, ptr null }, align 8
 
+declare void @harmless_use(ptr nocapture readonly) nofree norecurse nosync nounwind readnone willreturn nocallback
+
 ;.
 ; CHECK: @[[GLOBALS:[a-zA-Z0-9_$"\\.-]+]] = internal constant [[STRUCT_S:%.*]] { i32 42, double 3.140000e+00, ptr null }, align 8
 ;.
 define i32 @testOneFieldGlobalS() {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind readnone willreturn
 ; CHECK-LABEL: define {{[^@]+}}@testOneFieldGlobalS
-; CHECK-SAME: () #[[ATTR0:[0-9]+]] {
+; CHECK-SAME: () #[[ATTR1:[0-9]+]] {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br label [[IF_END:%.*]]
 ; CHECK:       if.then:
@@ -54,6 +56,7 @@ define i32 @testOneFieldGlobalS() {
 ;
 entry:
   %i = load i32, ptr @GlobalS, align 8
+  call void @harmless_use(ptr @GlobalS)
   %cmp = icmp ne i32 %i, 42
   br i1 %cmp, label %if.then, label %if.end
 
@@ -89,7 +92,7 @@ if.end7:                                          ; preds = %if.then5, %if.end4
 define i32 @testOneFieldGlobalS_type_mismatch() {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind readnone willreturn
 ; CHECK-LABEL: define {{[^@]+}}@testOneFieldGlobalS_type_mismatch
-; CHECK-SAME: () #[[ATTR0]] {
+; CHECK-SAME: () #[[ATTR1]] {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[I:%.*]] = load double, ptr @GlobalS, align 8
 ; CHECK-NEXT:    [[IC:%.*]] = fptosi double [[I]] to i32
@@ -155,7 +158,7 @@ if.end7:                                          ; preds = %if.then5, %if.end4
 define i32 @testOneFieldGlobalS_byte_offset_wrong() {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind readnone willreturn
 ; CHECK-LABEL: define {{[^@]+}}@testOneFieldGlobalS_byte_offset_wrong
-; CHECK-SAME: () #[[ATTR0]] {
+; CHECK-SAME: () #[[ATTR1]] {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[I:%.*]] = load i32, ptr getelementptr inbounds (i32, ptr @GlobalS, i32 1), align 8
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[I]], 42
@@ -217,5 +220,6 @@ if.end7:                                          ; preds = %if.then5, %if.end4
   ret i32 %r.2
 }
 ;.
-; CHECK: attributes #[[ATTR0]] = { nofree norecurse nosync nounwind readnone willreturn }
+; CHECK: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree norecurse nosync nounwind readnone willreturn }
+; CHECK: attributes #[[ATTR1]] = { nofree norecurse nosync nounwind readnone willreturn }
 ;.

llvm/test/Transforms/OpenMP/parallel_deletion.ll

@@ -279,6 +279,7 @@ entry:
 ;
 ; FIXME: We do not realize that `a` is dead and all accesses to it can be removed
 ;        making the parallel regions readonly and deletable.
+;        This is still true except the (non-atomic) reduction update is already deleted.
 define void @delete_parallel_2() {
 ; CHECK-LABEL: define {{[^@]+}}@delete_parallel_2() {
 ; CHECK-NEXT:  entry:
@@ -553,10 +554,6 @@ define internal void @.omp_outlined..6(i32* noalias %.global_tid., i32* noalias
 ; CHECK-NEXT:    i32 2, label [[DOTOMP_REDUCTION_CASE2:%.*]]
 ; CHECK-NEXT:    ]
 ; CHECK:       .omp.reduction.case1:
-; CHECK-NEXT:    [[TMP5:%.*]] = load i32, i32* [[A]], align 4
-; CHECK-NEXT:    [[TMP6:%.*]] = load i32, i32* [[A1]], align 4
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[TMP5]], [[TMP6]]
-; CHECK-NEXT:    store i32 [[ADD]], i32* [[A]], align 4
 ; CHECK-NEXT:    call void @__kmpc_end_reduce_nowait(%struct.ident_t* noundef nonnull @[[GLOB2]], i32 [[TMP2]], [8 x i32]* noundef nonnull @.gomp_critical_user_.reduction.var)
 ; CHECK-NEXT:    br label [[DOTOMP_REDUCTION_DEFAULT]]
 ; CHECK:       .omp.reduction.case2: