[llvm] [Attributor] Fix an issue that an access is skipped by mistake (PR #101862)

[Shilei Tian via llvm-commits]

https://github.com/shiltian updated https://github.com/llvm/llvm-project/pull/101862

>From 8c53a8baa0a39f08364ae6f3646d11b08738658e Mon Sep 17 00:00:00 2001
From: Shilei Tian <i at tianshilei.me>
Date: Sat, 3 Aug 2024 23:30:59 -0400
Subject: [PATCH] [Attributor] Fix an issue that an access is skipped by
 mistake

When we check if an access can be skipped, there is a case that an
inter-procedural interference access exists after a dominant write. Currently we
rely on `AAInterFnReachability` to tell if the access can be reachable. If it is
not, we can safely skip the access. However, it is based on an assumption that
the AA exists. It is possible that the AA doesn't exist. In this case, we can't
safely assume the acess can be skipped because we have to assume the access can
reach. This can happen when `AAInterFnReachability` is not in the allowed AA
list when creating the attributor, such as AMDGPUAttributor.
---
 .../Transforms/IPO/AttributorAttributes.cpp   |  2 +-
 .../indirect-call-set-from-other-function.ll  | 73 +++++++++++++++++++
 2 files changed, 74 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/CodeGen/AMDGPU/indirect-call-set-from-other-function.ll

diff --git a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
index cd31c4be1c1da..1a551faec6dff 100644
--- a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
+++ b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -1331,7 +1331,7 @@ struct AAPointerInfoImpl
         // itself either.
         bool Inserted = ExclusionSet.insert(&I).second;
 
-        if (!FnReachabilityAA ||
+        if (FnReachabilityAA &&
             !FnReachabilityAA->instructionCanReach(
                 A, *LeastDominatingWriteInst,
                 *Acc.getRemoteInst()->getFunction(), &ExclusionSet))
diff --git a/llvm/test/CodeGen/AMDGPU/indirect-call-set-from-other-function.ll b/llvm/test/CodeGen/AMDGPU/indirect-call-set-from-other-function.ll
new file mode 100644
index 0000000000000..f419d89a7f0a4
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/indirect-call-set-from-other-function.ll
@@ -0,0 +1,73 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --check-globals
+; RUN: opt -S -mtriple=amdgcn-amd-amdhsa -passes=amdgpu-attributor %s -o - | FileCheck %s
+
+ at g_fn = addrspace(1) global ptr null
+
+;.
+; CHECK: @g_fn = addrspace(1) global ptr null
+;.
+define void @set_fn(ptr %fn) {
+; CHECK-LABEL: define {{[^@]+}}@set_fn
+; CHECK-SAME: (ptr [[FN:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    store ptr [[FN]], ptr addrspace(1) @g_fn, align 8
+; CHECK-NEXT:    ret void
+;
+entry:
+  store ptr %fn, ptr addrspace(1) @g_fn
+  ret void
+}
+
+define void @get_fn(ptr %fn) {
+; CHECK-LABEL: define {{[^@]+}}@get_fn
+; CHECK-SAME: (ptr [[FN:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[LOAD:%.*]] = load ptr, ptr addrspace(1) @g_fn, align 8
+; CHECK-NEXT:    store ptr [[LOAD]], ptr [[FN]], align 8
+; CHECK-NEXT:    ret void
+;
+entry:
+  %load = load ptr, ptr addrspace(1) @g_fn
+  store ptr %load, ptr %fn
+  ret void
+}
+
+define void @foo() {
+; CHECK-LABEL: define {{[^@]+}}@foo
+; CHECK-SAME: () #[[ATTR1:[0-9]+]] {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[FN:%.*]] = alloca ptr, align 8, addrspace(5)
+; CHECK-NEXT:    store ptr null, ptr addrspace(5) [[FN]], align 8
+; CHECK-NEXT:    [[FN_CAST:%.*]] = addrspacecast ptr addrspace(5) [[FN]] to ptr
+; CHECK-NEXT:    call void @get_fn(ptr [[FN_CAST]])
+; CHECK-NEXT:    [[LOAD:%.*]] = load ptr, ptr addrspace(5) [[FN]], align 8
+; CHECK-NEXT:    [[TOBOOL:%.*]] = icmp ne ptr [[LOAD]], null
+; CHECK-NEXT:    br i1 [[TOBOOL]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    [[LOAD_1:%.*]] = load ptr, ptr addrspace(5) [[FN]], align 8
+; CHECK-NEXT:    call void [[LOAD_1]]()
+; CHECK-NEXT:    br label [[IF_END]]
+; CHECK:       if.end:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %fn = alloca ptr, addrspace(5)
+  store ptr null, ptr addrspace(5) %fn
+  %fn.cast = addrspacecast ptr addrspace(5) %fn to ptr
+  call void @get_fn(ptr %fn.cast)
+  %load = load ptr, ptr addrspace(5) %fn
+  %tobool = icmp ne ptr %load, null
+  br i1 %tobool, label %if.then, label %if.end
+
+if.then:
+  %load.1 = load ptr, ptr addrspace(5) %fn
+  call void %load.1()
+  br label %if.end
+
+if.end:
+  ret void
+}
+;.
+; CHECK: attributes #[[ATTR0]] = { "amdgpu-no-agpr" "amdgpu-no-completion-action" "amdgpu-no-default-queue" "amdgpu-no-dispatch-id" "amdgpu-no-dispatch-ptr" "amdgpu-no-heap-ptr" "amdgpu-no-hostcall-ptr" "amdgpu-no-implicitarg-ptr" "amdgpu-no-lds-kernel-id" "amdgpu-no-multigrid-sync-arg" "amdgpu-no-queue-ptr" "amdgpu-no-workgroup-id-x" "amdgpu-no-workgroup-id-y" "amdgpu-no-workgroup-id-z" "amdgpu-no-workitem-id-x" "amdgpu-no-workitem-id-y" "amdgpu-no-workitem-id-z" "amdgpu-waves-per-eu"="4,10" "uniform-work-group-size"="false" }
+; CHECK: attributes #[[ATTR1]] = { "amdgpu-waves-per-eu"="4,10" "uniform-work-group-size"="false" }
+;.