Don't emit relax relocs like R_X86_64_REX_GOTPCRELX on X86 target for OPENMP internal vars.

[UmeshKalappa0]

For kernel modules (where -fno-pic and no-pie is implicit ) having "R_X86_64_REX_GOTPCRELX " relocs burden the kernel loader to handle the same like https://godbolt.org/z/hhh7ozojz.

Solution : Mark the OpenMP internal variables with dso_local conditionally for no-pic and no-pie ,then

1. reset the dso_local for thread_local and weak linkage internal vars.

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Author: None (UmeshKalappa0)

Changes

For kernel modules (where -fno-pic and no-pie is implicit ) having "R_X86_64_REX_GOTPCRELX " relocs burden the kernel loader to handle the same like https://godbolt.org/z/hhh7ozojz.

Solution : Mark the OpenMP internal variables with dso_local conditionally for no-pic and no-pie ,then

1. reset the dso_local for thread_local and weak linkage internal vars.

---

Full diff: https://github.com/llvm/llvm-project/pull/75564.diff

1 Files Affected:

• (added) clang/test/OpenMP/gomp_critical_dso_local_var.c (+23)

diff --git a/clang/test/OpenMP/gomp_critical_dso_local_var.c b/clang/test/OpenMP/gomp_critical_dso_local_var.c
new file mode 100644
index 00000000000000..915f6773bf67bf
--- /dev/null
+++ b/clang/test/OpenMP/gomp_critical_dso_local_var.c
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -fopenmp -x c -emit-llvm %s -o - | FileCheck %s --check-prefix=DSO_LOCAL
+
+// DSO_LOCAL-DAG: @.gomp_critical_user_.var = common dso_local global [8 x i32] zeroinitializer, align 8
+int omp_critical_test()
+{
+  int sum;
+  int known_sum;
+
+  sum=0;
+#pragma omp parallel
+  {
+    int mysum=0;
+    int i;
+#pragma omp for
+    for (i = 0; i < 1000; i++)
+      mysum = mysum + i;
+#pragma omp critical
+    sum = mysum +sum;
+  }
+  known_sum = 999 * 1000 / 2;
+  return (known_sum == sum);
+}
+

[efriedma-quic]

Scattering around setDSOLocal(false) makes the logic hard to understand. I'd strongly prefer to fix the initial setting of dso_local when we create the global variable. We can refactor the code to make that work.

[UmeshKalappa0]

Scattering around setDSOLocal(false) makes the logic hard to understand. I'd strongly prefer to fix the initial setting of dso_local when we create the global variable. We can refactor the code to make that work.

@efriedma-quic ,thank you for the suggestions and was not sure about adding dso_local for openmp weak linkage vars ,but from the weak semantics point ,its ok to add the dso_local for no-pic /no-pie code ,so updated changes accordingly .

[mahtohappy]

Hi @UmeshKalappa0 why did you close this? This is still needed for us internally.