[Attributor] Teach AANoCapture to use information in-flight more aggressively
AAReturnedValues, AAMemoryBehavior, and AANoUnwind, can provide
information that helps during the tracking or even justifies no-capture.
We now use this information and enable no-capture in some test cases
designed a long while a ago for these cases.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@375382 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/Attributor.cpp b/lib/Transforms/IPO/Attributor.cpp
index 11a54bd..e7b7404 100644
--- a/lib/Transforms/IPO/Attributor.cpp
+++ b/lib/Transforms/IPO/Attributor.cpp
@@ -2939,7 +2939,7 @@
// Check what state the associated function can actually capture.
if (F)
- determineFunctionCaptureCapabilities(*F, *this);
+ determineFunctionCaptureCapabilities(IRP, *F, *this);
else
indicatePessimisticFixpoint();
}
@@ -2965,7 +2965,8 @@
/// Set the NOT_CAPTURED_IN_MEM and NOT_CAPTURED_IN_RET bits in \p Known
/// depending on the ability of the function associated with \p IRP to capture
/// state in memory and through "returning/throwing", respectively.
- static void determineFunctionCaptureCapabilities(const Function &F,
+ static void determineFunctionCaptureCapabilities(const IRPosition &IRP,
+ const Function &F,
IntegerState &State) {
// TODO: Once we have memory behavior attributes we should use them here.
@@ -2987,6 +2988,21 @@
// exceptions and doesn not return values.
if (F.doesNotThrow() && F.getReturnType()->isVoidTy())
State.addKnownBits(NOT_CAPTURED_IN_RET);
+
+ // Check existing "returned" attributes.
+ int ArgNo = IRP.getArgNo();
+ if (F.doesNotThrow() && ArgNo >= 0) {
+ for (unsigned u = 0, e = F.arg_size(); u< e; ++u)
+ if (F.hasParamAttribute(u, Attribute::Returned)) {
+ if (u == ArgNo)
+ State.removeAssumedBits(NOT_CAPTURED_IN_RET);
+ else if (F.onlyReadsMemory())
+ State.addKnownBits(NO_CAPTURE);
+ else
+ State.addKnownBits(NOT_CAPTURED_IN_RET);
+ break;
+ }
+ }
}
/// See AbstractState::getAsStr().
@@ -3158,15 +3174,54 @@
const Function *F =
getArgNo() >= 0 ? IRP.getAssociatedFunction() : IRP.getAnchorScope();
assert(F && "Expected a function!");
- const auto &IsDeadAA = A.getAAFor<AAIsDead>(*this, IRPosition::function(*F));
+ const IRPosition &FnPos = IRPosition::function(*F);
+ const auto &IsDeadAA = A.getAAFor<AAIsDead>(*this, FnPos);
AANoCapture::StateType T;
- // TODO: Once we have memory behavior attributes we should use them here
- // similar to the reasoning in
- // AANoCaptureImpl::determineFunctionCaptureCapabilities(...).
- // TODO: Use the AAReturnedValues to learn if the argument can return or
- // not.
+ // Readonly means we cannot capture through memory.
+ const auto &FnMemAA = A.getAAFor<AAMemoryBehavior>(*this, FnPos);
+ if (FnMemAA.isAssumedReadOnly()) {
+ T.addKnownBits(NOT_CAPTURED_IN_MEM);
+ if (FnMemAA.isKnownReadOnly())
+ addKnownBits(NOT_CAPTURED_IN_MEM);
+ }
+
+ // Make sure all returned values are different than the underlying value.
+ // TODO: we could do this in a more sophisticated way inside
+ // AAReturnedValues, e.g., track all values that escape through returns
+ // directly somehow.
+ auto CheckReturnedArgs = [&](const AAReturnedValues &RVAA) {
+ bool SeenConstant = false;
+ for (auto &It : RVAA.returned_values()) {
+ if (isa<Constant>(It.first)) {
+ if (SeenConstant)
+ return false;
+ SeenConstant = true;
+ } else if (!isa<Argument>(It.first) ||
+ It.first == getAssociatedArgument())
+ return false;
+ }
+ return true;
+ };
+
+ const auto &NoUnwindAA = A.getAAFor<AANoUnwind>(*this, FnPos);
+ if (NoUnwindAA.isAssumedNoUnwind()) {
+ bool IsVoidTy = F->getReturnType()->isVoidTy();
+ const AAReturnedValues *RVAA =
+ IsVoidTy ? nullptr : &A.getAAFor<AAReturnedValues>(*this, FnPos);
+ if (IsVoidTy || CheckReturnedArgs(*RVAA)) {
+ T.addKnownBits(NOT_CAPTURED_IN_RET);
+ if (T.isKnown(NOT_CAPTURED_IN_MEM))
+ return ChangeStatus::UNCHANGED;
+ if (NoUnwindAA.isKnownNoUnwind() &&
+ (IsVoidTy || RVAA->getState().isAtFixpoint())) {
+ addKnownBits(NOT_CAPTURED_IN_RET);
+ if (isKnown(NOT_CAPTURED_IN_MEM))
+ return indicateOptimisticFixpoint();
+ }
+ }
+ }
// Use the CaptureTracker interface and logic with the specialized tracker,
// defined in AACaptureUseTracker, that can look at in-flight abstract
diff --git a/test/Transforms/FunctionAttrs/arg_nocapture.ll b/test/Transforms/FunctionAttrs/arg_nocapture.ll
index 18050db..7afaab6 100644
--- a/test/Transforms/FunctionAttrs/arg_nocapture.ll
+++ b/test/Transforms/FunctionAttrs/arg_nocapture.ll
@@ -405,35 +405,33 @@
;
; Make sure the returned flag on %r is strong enough to justify nocapture on %b but **not** on %r.
;
-; FIXME: The "returned" information is not propagated to the fullest extend causing us to miss "nocapture" on %b in the following:
-; CHECK: define i32* @not_captured_by_readonly_call_not_returned_either1(i32* readonly %b, i32* readonly returned %r)
+; CHECK: define i32* @not_captured_by_readonly_call_not_returned_either1(i32* nocapture readonly %b, i32* readonly returned %r)
;
-; CHECK: define i32* @not_captured_by_readonly_call_not_returned_either2(i32* readonly %b, i32* readonly returned %r)
-; CHECK: define i32* @not_captured_by_readonly_call_not_returned_either3(i32* readonly %b, i32* readonly returned %r)
+; CHECK: define i32* @not_captured_by_readonly_call_not_returned_either2(i32* nocapture readonly %b, i32* readonly returned %r)
+; CHECK: define i32* @not_captured_by_readonly_call_not_returned_either3(i32* nocapture readonly %b, i32* readonly returned %r)
;
-; FIXME: The "nounwind" information is not derived to the fullest extend causing us to miss "nocapture" on %b in the following:
-; CHECK: define i32* @not_captured_by_readonly_call_not_returned_either4(i32* readonly %b, i32* readonly returned %r)
-define i32* @not_captured_by_readonly_call_not_returned_either1(i32* %b, i32* returned %r) #0 {
+; CHECK: define i32* @not_captured_by_readonly_call_not_returned_either4(i32* nocapture readonly %b, i32* readonly returned %r)
+define i32* @not_captured_by_readonly_call_not_returned_either1(i32* %b, i32* returned %r) {
entry:
%call = call i32* @readonly_unknown(i32* %b, i32* %r) nounwind
ret i32* %call
}
declare i32* @readonly_unknown_r1a(i32*, i32* returned) readonly
-define i32* @not_captured_by_readonly_call_not_returned_either2(i32* %b, i32* %r) #0 {
+define i32* @not_captured_by_readonly_call_not_returned_either2(i32* %b, i32* %r) {
entry:
%call = call i32* @readonly_unknown_r1a(i32* %b, i32* %r) nounwind
ret i32* %call
}
declare i32* @readonly_unknown_r1b(i32*, i32* returned) readonly nounwind
-define i32* @not_captured_by_readonly_call_not_returned_either3(i32* %b, i32* %r) #0 {
+define i32* @not_captured_by_readonly_call_not_returned_either3(i32* %b, i32* %r) {
entry:
%call = call i32* @readonly_unknown_r1b(i32* %b, i32* %r)
ret i32* %call
}
-define i32* @not_captured_by_readonly_call_not_returned_either4(i32* %b, i32* %r) #0 {
+define i32* @not_captured_by_readonly_call_not_returned_either4(i32* %b, i32* %r) nounwind {
entry:
%call = call i32* @readonly_unknown_r1a(i32* %b, i32* %r)
ret i32* %call
diff --git a/test/Transforms/FunctionAttrs/arg_returned.ll b/test/Transforms/FunctionAttrs/arg_returned.ll
index 3fe960c..d927cdf 100644
--- a/test/Transforms/FunctionAttrs/arg_returned.ll
+++ b/test/Transforms/FunctionAttrs/arg_returned.ll
@@ -1,5 +1,5 @@
; RUN: opt -functionattrs -S < %s | FileCheck %s --check-prefix=FNATTR
-; RUN: opt -attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=6 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
+; RUN: opt -attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=7 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
; RUN: opt -attributor -attributor-manifest-internal -attributor-disable=false -functionattrs -S < %s | FileCheck %s --check-prefix=BOTH
;
; Test cases specifically designed for the "returned" argument attribute.
diff --git a/test/Transforms/FunctionAttrs/nocapture.ll b/test/Transforms/FunctionAttrs/nocapture.ll
index e058084..f8927a6 100644
--- a/test/Transforms/FunctionAttrs/nocapture.ll
+++ b/test/Transforms/FunctionAttrs/nocapture.ll
@@ -39,6 +39,20 @@
ret i1 1 ; escaping value not caught by def-use chaining.
}
+; c4b is c4 but without the escaping part
+; FNATTR: define i1 @c4b(i32* %q, i32 %bitno)
+; ATTRIBUTOR: define i1 @c4b(i32* nocapture readnone %q, i32 %bitno)
+define i1 @c4b(i32* %q, i32 %bitno) {
+ %tmp = ptrtoint i32* %q to i32
+ %tmp2 = lshr i32 %tmp, %bitno
+ %bit = trunc i32 %tmp2 to i1
+ br i1 %bit, label %l1, label %l0
+l0:
+ ret i1 0 ; not escaping!
+l1:
+ ret i1 0 ; not escaping!
+}
+
@lookup_table = global [2 x i1] [ i1 0, i1 1 ]
; FNATTR: define i1 @c5(i32* %q, i32 %bitno)
@@ -331,5 +345,20 @@
ret void
}
+declare i8* @unknownpi8pi8(i8*,i8* returned)
+define i8* @test_returned1(i8* %A, i8* returned %B) nounwind readonly {
+; ATTRIBUTOR: define i8* @test_returned1(i8* nocapture readonly %A, i8* readonly returned %B)
+entry:
+ %p = call i8* @unknownpi8pi8(i8* %A, i8* %B)
+ ret i8* %p
+}
+
+define i8* @test_returned2(i8* %A, i8* %B) {
+; ATTRIBUTOR: define i8* @test_returned2(i8* nocapture readonly %A, i8* readonly returned %B)
+entry:
+ %p = call i8* @unknownpi8pi8(i8* %A, i8* %B) nounwind readonly
+ ret i8* %p
+}
+
declare i8* @llvm.launder.invariant.group.p0i8(i8*)
declare i8* @llvm.strip.invariant.group.p0i8(i8*)
diff --git a/test/Transforms/FunctionAttrs/nonnull.ll b/test/Transforms/FunctionAttrs/nonnull.ll
index 84d6720..9a7eb11 100644
--- a/test/Transforms/FunctionAttrs/nonnull.ll
+++ b/test/Transforms/FunctionAttrs/nonnull.ll
@@ -220,7 +220,7 @@
define dso_local noalias i32* @f3(i32* %arg) {
; FIXME: missing nonnull. It should be nonnull @f3(i32* nonnull readonly %arg)
-; ATTRIBUTOR: define dso_local noalias i32* @f3(i32* readonly %arg)
+; ATTRIBUTOR: define dso_local noalias i32* @f3(i32* nocapture readonly %arg)
bb:
; FIXME: missing nonnull. It should be @f1(i32* nonnull readonly %arg)
; ATTRIBUTOR: %tmp = call i32* @f1(i32* readonly %arg)
diff --git a/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll b/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll
index 5f9e477..6fbc545 100644
--- a/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll
+++ b/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll
@@ -1,4 +1,4 @@
-; RUN: opt -functionattrs -enable-nonnull-arg-prop -attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=7 -S < %s | FileCheck %s
+; RUN: opt -functionattrs -enable-nonnull-arg-prop -attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=8 -S < %s | FileCheck %s
;
; This is an evolved example to stress test SCC parameter attribute propagation.
; The SCC in this test is made up of the following six function, three of which
