[llvm] ValueTracking: Skip threadlocal.address in computeKnownBits (PR #88435)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-analysis

Author: Matthias Braun (MatzeB)

<details>
<summary>Changes</summary>

Look through `llvm.threadlocal.address` intrinsic when computing known bits in ValueTracking.

This improves issue #<!-- -->87437

---
Full diff: https://github.com/llvm/llvm-project/pull/88435.diff


2 Files Affected:

- (modified) llvm/lib/Analysis/ValueTracking.cpp (+4) 
- (added) llvm/test/Analysis/ValueTracking/knownbits-tls.ll (+32) 


``````````diff
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 3a10de72a27562..c7aec8518044f3 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1686,6 +1686,10 @@ static void computeKnownBitsFromOperator(const Operator *I,
           Known.Zero.setBitsFrom(KnownZeroFirstBit);
         break;
       }
+      case Intrinsic::threadlocal_address: {
+        computeKnownBits(II->getArgOperand(0), Known, Depth + 1, Q);
+        break;
+      }
       case Intrinsic::vscale: {
         if (!II->getParent() || !II->getFunction())
           break;
diff --git a/llvm/test/Analysis/ValueTracking/knownbits-tls.ll b/llvm/test/Analysis/ValueTracking/knownbits-tls.ll
new file mode 100644
index 00000000000000..203777c33f8486
--- /dev/null
+++ b/llvm/test/Analysis/ValueTracking/knownbits-tls.ll
@@ -0,0 +1,32 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -S -passes=instcombine < %s | FileCheck %s
+
+target datalayout = "p:64:64"
+
+ at tlsvar_align32 = thread_local global i32 3, align 32
+
+define i1 @lowbits_zero() {
+; CHECK-LABEL: define i1 @lowbits_zero() {
+; CHECK-NEXT:    ret i1 true
+;
+  %p = call ptr @llvm.threadlocal.address(ptr @tlsvar_align32)
+  %p_int = ptrtoint ptr %p to i64
+  %lowbits = and i64 %p_int, 31
+  %lowbits_zero = icmp eq i64 %lowbits, 0
+  ret i1 %lowbits_zero
+}
+
+define i1 @lowbits_unknown() {
+; CHECK-LABEL: define i1 @lowbits_unknown() {
+; CHECK-NEXT:    [[P:%.*]] = call ptr @llvm.threadlocal.address.p0(ptr @tlsvar_align32)
+; CHECK-NEXT:    [[P_INT:%.*]] = ptrtoint ptr [[P]] to i64
+; CHECK-NEXT:    [[LOWBITS:%.*]] = and i64 [[P_INT]], 32
+; CHECK-NEXT:    [[LOWBITS_ZERO:%.*]] = icmp eq i64 [[LOWBITS]], 0
+; CHECK-NEXT:    ret i1 [[LOWBITS_ZERO]]
+;
+  %p = call ptr @llvm.threadlocal.address(ptr @tlsvar_align32)
+  %p_int = ptrtoint ptr %p to i64
+  %lowbits = and i64 %p_int, 63
+  %lowbits_zero = icmp eq i64 %lowbits, 0
+  ret i1 %lowbits_zero
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/88435