[flang] [llvm] [OpenMP][][LLVM] Update alloca IP after `PrivCB` in `OMPIRBUIlder` (PR #93920)

[Kareem Ergawy via llvm-commits]

https://github.com/ergawy created https://github.com/llvm/llvm-project/pull/93920

Fixes a crash uncovered by [pr77666.f90](https://github.com/llvm/llvm-test-suite/blob/main/Fortran/gfortran/regression/gomp/pr77666.f90) in the test suite.

In particular, whenever `PrivCB` (the callback responsible for generating privatizaiton logic for an OMP variable) generates a multi-block privatization region, the insertion point diverges: the BB component of the IP can become a different BB from the parent block of the instruction iterator component of the IP. This PR updates the IP to make sure that the BB is the parent block of the instruction iterator.

>From e4dfb33701e9b2cb68e84a3851169beb48404413 Mon Sep 17 00:00:00 2001
From: ergawy <kareem.ergawy at amd.com>
Date: Thu, 30 May 2024 23:16:39 -0500
Subject: [PATCH] [OpenMP][][LLVM] Update alloca IP after `PrivCB` in
 `OMPIRBUIlder`

Fixes a crash uncovered by [pr77666.f90](https://github.com/llvm/llvm-test-suite/blob/main/Fortran/gfortran/regression/gomp/pr77666.f90) in the test suite.

In particular, whenever `PrivCB` (the callback responsible for
generating privatizaiton logic for an OMP variable) generates a
multi-block privatization region, the insertion point diverges: the BB
component of the IP can become a different BB from the parent block of
the instruction iterator component of the IP. This PR updates the IP to
make sure that the BB is the parent block of the instruction iterator.
---
 ...rivatization-lower-allocatable-to-llvm.f90 | 20 +++++++++++++++++++
 llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp     |  3 +++
 2 files changed, 23 insertions(+)
 create mode 100644 flang/test/Lower/OpenMP/delayed-privatization-lower-allocatable-to-llvm.f90

diff --git a/flang/test/Lower/OpenMP/delayed-privatization-lower-allocatable-to-llvm.f90 b/flang/test/Lower/OpenMP/delayed-privatization-lower-allocatable-to-llvm.f90
new file mode 100644
index 0000000000000..0363494c59ecf
--- /dev/null
+++ b/flang/test/Lower/OpenMP/delayed-privatization-lower-allocatable-to-llvm.f90
@@ -0,0 +1,20 @@
+! RUN: %flang -S -emit-llvm -fopenmp -mmlir --openmp-enable-delayed-privatization \
+! RUN:   -o - %s 2>&1 | FileCheck %s
+
+subroutine foo(x)
+  integer, allocatable :: x, y
+!$omp parallel private(x, y)
+  x = y
+!$omp end parallel
+end
+
+! CHECK-LABEL: define void @foo_
+! CHECK:         ret void
+! CHECK-NEXT:  }
+
+! CHECK-LABEL: define internal void @foo_..omp_par
+! CHECK-DAG:     call ptr @malloc
+! CHECK-DAG:     call ptr @malloc
+! CHECK-DAG:     call void @free
+! CHECK-DAG:     call void @free
+! CHECK:       }
diff --git a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
index cb4de9c8876dc..eab41eb8a35b2 100644
--- a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
+++ b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
@@ -1583,6 +1583,9 @@ IRBuilder<>::InsertPoint OpenMPIRBuilder::createParallel(
     } else {
       Builder.restoreIP(
           PrivCB(InnerAllocaIP, Builder.saveIP(), V, *Inner, ReplacementValue));
+      InnerAllocaIP = {InnerAllocaIP.getPoint()->getParent(),
+                       InnerAllocaIP.getPoint()};
+
       assert(ReplacementValue &&
              "Expected copy/create callback to set replacement value!");
       if (ReplacementValue == &V)