[Attributor] Bail early if AAMemoryLocation cannot derive anything

Before this change we looked through all memory operations in a function
even if the first was an unknown call that could do anything. This did
cost a lot of time but there is little use to do so. We also avoid
creating AAs for things that we would have looked at in case no other AA
will; that is the reason for the test changes.

Running only the attributor-cgscc pass on a IR version of
`llvm-test-suite/MultiSource/Applications/SPASS/clause.c` reduced the
time we spend in `AAMemoryLocation::update` from 4% total to
0.9% (disclaimer: no accurate measurements).

Author: jdoerfert

llvm/lib/Transforms/IPO/AttributorAttributes.cpp

@@ -6628,7 +6628,9 @@ struct AAMemoryLocationFunction final : public AAMemoryLocationImpl {
       LLVM_DEBUG(dbgs() << "[AAMemoryLocation] Accessed locations for " << I
                         << ": " << getMemoryLocationsAsStr(MLK) << "\n");
       removeAssumedBits(inverseLocation(MLK, false, false));
-      return true;
+      // Stop once only the valid bit set in the *not assumed location*, thus
+      // once we don't actually exclude any memory locations in the state.
+      return getAssumedNotAccessedLocation() != VALID_STATE;
     };
 
     if (!A.checkForAllReadWriteInstructions(CheckRWInst, *this))

llvm/test/Transforms/Attributor/dereferenceable-1.ll

@@ -280,6 +280,7 @@ define void @f7_2(i1 %c) {
 ; CHECK-SAME: (i1 [[C:%.*]])
 ; CHECK-NEXT:    [[PTR:%.*]] = tail call nonnull align 4 dereferenceable(4) i32* @unkown_ptr()
 ; CHECK-NEXT:    [[A:%.*]] = tail call i32 @unkown_f(i32* nonnull align 4 dereferenceable(4) [[PTR]])
+; CHECK-NEXT:    [[ARG_A_0:%.*]] = load i32, i32* [[PTR]], align 4
 ; CHECK-NEXT:    [[B:%.*]] = tail call i32 @unkown_f(i32* nonnull align 4 dereferenceable(4) [[PTR]])
 ; CHECK-NEXT:    br i1 [[C]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
 ; CHECK:       if.true:

llvm/test/Transforms/Attributor/heap_to_stack.ll

@@ -450,10 +450,11 @@ 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:%.*]] = bitcast i32* [[TMP3]] to i8*
-; IS________OPM-NEXT:    call void @free(i8* nocapture [[TMP16]])
-; IS________OPM-NEXT:    [[TMP17:%.*]] = load i32, i32* [[TMP3]], align 4
-; IS________OPM-NEXT:    ret i32 [[TMP17]]
+; 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 [[TMP17]])
+; IS________OPM-NEXT:    [[TMP18:%.*]] = load i32, i32* [[TMP3]], align 4
+; IS________OPM-NEXT:    ret i32 [[TMP18]]
 ;
 ; IS________NPM-LABEL: define {{[^@]+}}@irreducible_cfg
 ; IS________NPM-SAME: (i32 [[TMP0:%.*]])

llvm/test/Transforms/Attributor/liveness.ll

@@ -1920,7 +1920,7 @@ define i32 @main() {
 ; CHECK-NEXT:    [[INC]] = add nuw nsw i32 [[G_0]], 1
 ; CHECK-NEXT:    br label [[FOR_COND_0]]
 ; CHECK:       for.end.0:
-; CHECK-NEXT:    [[CALL:%.*]] = call noalias i8* @malloc(i64 8)
+; CHECK-NEXT:    [[CALL:%.*]] = call i8* @malloc(i64 8)
 ; CHECK-NEXT:    store i8* [[CALL]], i8** bitcast (%struct.a** @e to i8**), align 8
 ; CHECK-NEXT:    [[B:%.*]] = bitcast i8* [[CALL]] to %struct.a**
 ; CHECK-NEXT:    store %struct.a* null, %struct.a** [[B]], align 8

llvm/test/Transforms/Attributor/noreturn_async.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes --check-attributes
-; RUN: opt -attributor  -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=2 -S < %s | FileCheck %s
+; RUN: opt -attributor  -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=1 -S < %s | FileCheck %s
 ;
 ; This file is the same as noreturn_sync.ll but with a personality which
 ; indicates that the exception handler *can* catch asynchronous exceptions. As