[flang-commits] [flang] [openmp] [OpenMP] [Flang] Fix Issue llvm#76121 (PR #82221)

[chandan singh via flang-commits]

https://github.com/chandankds updated https://github.com/llvm/llvm-project/pull/82221

>From 9b1ea42bd38b4ede10460bef569e80f30a73d115 Mon Sep 17 00:00:00 2001
From: chandan singh <chandankds at gmail.com>
Date: Mon, 19 Feb 2024 12:21:37 +0530
Subject: [PATCH 1/2] [OpenMP] [Flang] Fix Issue llvm#76121

Root cause: Segmentation fault is caused by null pointer dereference inside the __kmpc_fork_call_if function at https://github.com/llvm/llvm-project/blob/main/openmp/runtime/src/z_Linux_asm.S#L1186 . __kmpc_fork_call_if is missing case to handle argc=0 .

Fix: Added a check inside the __kmp_invoke_microtask function to handle the case when argc is 0.
---
 openmp/runtime/src/z_Linux_asm.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/openmp/runtime/src/z_Linux_asm.S b/openmp/runtime/src/z_Linux_asm.S
index 14987c298fa5f9..b44d9fb316a05c 100644
--- a/openmp/runtime/src/z_Linux_asm.S
+++ b/openmp/runtime/src/z_Linux_asm.S
@@ -1150,6 +1150,9 @@ KMP_LABEL(kmp_invoke_pass_parms):	// put 1st - 6th parms to pkfn in registers.
 	movq	%rdi, %rbx	// pkfn -> %rbx
 	leaq	__gtid(%rbp), %rdi // &gtid -> %rdi (store 1st parm to pkfn)
 	leaq	__tid(%rbp), %rsi  // &tid -> %rsi (store 2nd parm to pkfn)
+	// Check if argc is 0
+	cmpq $0, %rax
+	je KMP_LABEL(kmp_no_args) // Jump ahead
 
 	movq	%r8, %r11	// p_argv -> %r11
 
@@ -1195,6 +1198,7 @@ KMP_LABEL(kmp_1_exit):
 	cmovnsq	(%r11), %rdx	// p_argv[0] -> %rdx (store 3rd parm to pkfn)
 #endif // KMP_MIC
 
+	KMP_LABEL(kmp_no_args):
 	call	*%rbx		// call (*pkfn)();
 	movq	$1, %rax	// move 1 into return register;
 

>From 4f4fae3f9d4e28602461c0ffe882d1ed84002e39 Mon Sep 17 00:00:00 2001
From: Singh <chasingh at amd.com>
Date: Sun, 3 Mar 2024 08:21:21 +0530
Subject: [PATCH 2/2] Create parallel_do_if_false.f90

---
 flang/test/Runtime/parallel_do_if_false.f90 | 27 +++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 flang/test/Runtime/parallel_do_if_false.f90

diff --git a/flang/test/Runtime/parallel_do_if_false.f90 b/flang/test/Runtime/parallel_do_if_false.f90
new file mode 100644
index 00000000000000..f15a697eb5868d
--- /dev/null
+++ b/flang/test/Runtime/parallel_do_if_false.f90
@@ -0,0 +1,27 @@
+!RUN: %flang %s -o %t -fopenmp  && %t | FileCheck %s
+PROGRAM parallel_do_if
+
+        USE OMP_LIB
+
+        INTEGER :: I
+
+        INTEGER :: N = 0
+
+        INTEGER, PARAMETER :: NI = 1
+
+        !$OMP PARALLEL DO IF(.false.)
+
+        DO I = 1, NI
+
+        IF (omp_in_parallel() .EQV. .false.) THEN               
+                !CHECK: PASS
+                PRINT *, "PASS"
+        ELSE
+                PRINT *, "FAIL"
+
+        END IF
+
+        END DO
+        !$OMP END PARALLEL DO
+
+END PROGRAM