[Attributor] AAPointerInfo can model non-escaping call uses

If a call base use will not capture a pointer we can approximate the effects. This is important especially for readnone/only uses. Even may-write uses are not too bad with reachability in place. Capturing is the problem as we loose track of update sides.
llvm · Oct 5, 2022 · 93e51fa · 93e51fa
1 parent 1940c49
commit 93e51fa
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Showing 3 changed files with 37 additions and 10 deletions.
diff --git a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -1530,13 +1530,35 @@ 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);
+      if (!Arg->getParent()->isDeclaration())
+        return indicatePessimisticFixpoint();
+    }
+
+    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,
+                 AA::OffsetAndSize::Unknown, Changed, nullptr,
+                 AA::OffsetAndSize::Unknown);
+    return Changed;
   }
 
   /// See AbstractAttribute::trackStatistics()

diff --git a/llvm/test/Transforms/Attributor/heap_to_stack_gpu.ll b/llvm/test/Transforms/Attributor/heap_to_stack_gpu.ll
@@ -350,6 +350,7 @@ define void @test11() {
 
 ; TEST 12
 define i32 @irreducible_cfg(i32 %0) {
+;
 ; CHECK-LABEL: define {{[^@]+}}@irreducible_cfg
 ; CHECK-SAME: (i32 [[TMP0:%.*]]) {
 ; CHECK-NEXT:    [[TMP2:%.*]] = call noalias i8* @malloc(i64 noundef 4)

diff --git a/llvm/test/Transforms/Attributor/value-simplify-pointer-info-struct.ll b/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 }
 ;.