[llvm] GlobalsModRef, ValueTracking: Look through threadlocal.address intrinsic (PR #88418)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-analysis

Author: Matthias Braun (MatzeB)

<details>
<summary>Changes</summary>

Analyses should typically look through `threadlocal.address` intrinsic to get at the underlying `GlobalValue`. This fixes `GlobalsAAResult::AnalyzeUsesOfPointer` and `llvm::getUnderlyingObject`.

---
Full diff: https://github.com/llvm/llvm-project/pull/88418.diff


3 Files Affected:

- (modified) llvm/lib/Analysis/GlobalsModRef.cpp (+8) 
- (modified) llvm/lib/Analysis/ValueTracking.cpp (+6) 
- (modified) llvm/test/Analysis/GlobalsModRef/nonescaping-noalias.ll (+19) 


``````````diff
diff --git a/llvm/lib/Analysis/GlobalsModRef.cpp b/llvm/lib/Analysis/GlobalsModRef.cpp
index 527f19b194eeb9..1ceb1b26294183 100644
--- a/llvm/lib/Analysis/GlobalsModRef.cpp
+++ b/llvm/lib/Analysis/GlobalsModRef.cpp
@@ -344,6 +344,14 @@ bool GlobalsAAResult::AnalyzeUsesOfPointer(Value *V,
       if (AnalyzeUsesOfPointer(I, Readers, Writers, OkayStoreDest))
         return true;
     } else if (auto *Call = dyn_cast<CallBase>(I)) {
+      if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+        if (II->getIntrinsicID() == Intrinsic::threadlocal_address &&
+            V == II->getArgOperand(0)) {
+          if (AnalyzeUsesOfPointer(II, Readers, Writers))
+            return true;
+          continue;
+        }
+      }
       // Make sure that this is just the function being called, not that it is
       // passing into the function.
       if (Call->isDataOperand(&U)) {
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 3a10de72a27562..d25ebd80d2411d 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -6269,6 +6269,12 @@ const Value *llvm::getUnderlyingObject(const Value *V, unsigned MaxLookup) {
           continue;
         }
       } else if (auto *Call = dyn_cast<CallBase>(V)) {
+        if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(V)) {
+          if (II->getIntrinsicID() == Intrinsic::threadlocal_address) {
+            V = II->getArgOperand(0);
+            continue;
+          }
+        }
         // CaptureTracking can know about special capturing properties of some
         // intrinsics like launder.invariant.group, that can't be expressed with
         // the attributes, but have properties like returning aliasing pointer.
diff --git a/llvm/test/Analysis/GlobalsModRef/nonescaping-noalias.ll b/llvm/test/Analysis/GlobalsModRef/nonescaping-noalias.ll
index d109b3b8748ba7..f28e73c48b3e8e 100644
--- a/llvm/test/Analysis/GlobalsModRef/nonescaping-noalias.ll
+++ b/llvm/test/Analysis/GlobalsModRef/nonescaping-noalias.ll
@@ -22,6 +22,25 @@ entry:
   ret i32 %v
 }
 
+ at g1_tls = internal thread_local global i32 0
+
+define i32 @test1_tls(ptr %param) {
+; Ensure that we can fold a store to a load of a global across a store to
+; a parameter when the global is non-escaping.
+;
+; CHECK-LABEL: @test1_tls(
+; CHECK: %p = call ptr @llvm.threadlocal.address.p0(ptr @g1_tls)
+; CHECK: store i32 42, ptr %p
+; CHECK-NOT: load i32
+; CHECK: ret i32 42
+entry:
+  %p = call ptr @llvm.threadlocal.address(ptr @g1_tls)
+  store i32 42, ptr %p
+  store i32 7, ptr %param
+  %v = load i32, ptr %p
+  ret i32 %v
+}
+
 declare ptr @f()
 
 define i32 @test2() {

``````````

</details>


https://github.com/llvm/llvm-project/pull/88418