[PATCH] Fix for incorrect breakpoint set in case of flang compiled binary

["Sharma, Alok Kumar" <AlokKumar.Sharma@amd.com>]

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Hi All,

I request you all to please review this patch. Below are the details.

Problem Description:
Currently, GDB is not able to set a breakpoint at subprogram post
prologue for flang generated binaries. This is due to clang having
two line notes one before and another after the prologue.
Resolution:
 Now the end of prologue is determined using symbol table, which was
the way for clang generated binaries already. Since clang and flang
both share same back-end it is true for flang as well.

gdb/ChangeLog

      * amd64-tdep.c (amd64_skip_prologue): Using symbol table
      to find the end of prologue for flang compiled binaries.
      * arm-tdep.c (arm_skip_prologue): Likewise.
      * i386-tdep.c (i386_skip_prologue): Likewise.

gdb/testsuite/ChangeLog

      * gdb.fortran/vla-type.exp: Skip commands not required for
      the Flang compiled binaries after prologue fix.

Regards,
Alok

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From 6f578b992c789196478742b71af6b75fb76573f3 Mon Sep 17 00:00:00 2001
From: Alok Kumar Sharma <AlokKumar.Sharma@amd.com>
Date: Mon, 17 Aug 2020 17:04:11 +0530
Subject: [PATCH] Fix for incorrect breakpoint set in case of flang compiled
 binary

  Currently, GDB is not able to set a breakpoint at subprogram post
prologue for flang generated binaries. This is due to clang having
two line notes one before and another after the prologue.
  Now the end of prologue is determined using symbol table, which was
the way for clang generated binaries already. Since clang and flang
both share same back-end it is true for flang as well.

gdb/ChangeLog

      * amd64-tdep.c (amd64_skip_prologue): Using symbol table
      to find the end of prologue for flang compiled binaries.
      * arm-tdep.c (arm_skip_prologue): Likewise.
      * i386-tdep.c (i386_skip_prologue): Likewise.

gdb/testsuite/ChangeLog

      * gdb.fortran/vla-type.exp: Skip commands not required for
      the Flang compiled binaries after prologue fix.

Change-Id: I5609f979315effc213feeb6dde6a01a024e0c487
---
 gdb/ChangeLog                          | 7 +++++++
 gdb/amd64-tdep.c                       | 5 +++--
 gdb/arm-tdep.c                         | 3 ++-
 gdb/i386-tdep.c                        | 5 +++--
 gdb/testsuite/ChangeLog                | 5 +++++
 gdb/testsuite/gdb.fortran/vla-type.exp | 8 ++++++--
 6 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 3e733a73f0..3eb07cb5d0 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2020-08-14  Alok Kumar Sharma  <AlokKumar.Sharma@amd.com>
+
+	* amd64-tdep.c (amd64_skip_prologue): Using symbol table
+	to find the end of prologue for flang compiled binaries.
+	* arm-tdep.c (arm_skip_prologue): Likewise.
+	* i386-tdep.c (i386_skip_prologue): Likewise.
+
 2020-08-17  Tom de Vries  <tdevries@suse.de>
 
 	PR gdb/26393
diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
index 768fe63bdd..6f05f60548 100644
--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -2547,12 +2547,13 @@ amd64_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR start_pc)
 	= skip_prologue_using_sal (gdbarch, func_addr);
       struct compunit_symtab *cust = find_pc_compunit_symtab (func_addr);
 
-      /* Clang always emits a line note before the prologue and another
+      /* Clang/Flang always emit a line note before the prologue and another
 	 one after.  We trust clang to emit usable line notes.  */
       if (post_prologue_pc
 	  && (cust != NULL
 	      && COMPUNIT_PRODUCER (cust) != NULL
-	      && startswith (COMPUNIT_PRODUCER (cust), "clang ")))
+	      && (startswith (COMPUNIT_PRODUCER (cust), "clang ")
+	          || startswith(COMPUNIT_PRODUCER(cust), " F90 Flang"))))
         return std::max (start_pc, post_prologue_pc);
     }
 
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 9cedcc8575..27a8b519ed 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -1351,7 +1351,8 @@ arm_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
 	  && (cust == NULL
 	      || COMPUNIT_PRODUCER (cust) == NULL
 	      || startswith (COMPUNIT_PRODUCER (cust), "GNU ")
-	      || startswith (COMPUNIT_PRODUCER (cust), "clang ")))
+	      || startswith (COMPUNIT_PRODUCER (cust), "clang ")
+	      || startswith (COMPUNIT_PRODUCER (cust), " F90 Flang")))
 	return post_prologue_pc;
 
       if (post_prologue_pc != 0)
diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index 9b905c1996..4c1cf3acd7 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -1847,12 +1847,13 @@ i386_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR start_pc)
 	= skip_prologue_using_sal (gdbarch, func_addr);
       struct compunit_symtab *cust = find_pc_compunit_symtab (func_addr);
 
-      /* Clang always emits a line note before the prologue and another
+      /* Clang/Flang always emit a line note before the prologue and another
 	 one after.  We trust clang to emit usable line notes.  */
       if (post_prologue_pc
 	  && (cust != NULL
 	      && COMPUNIT_PRODUCER (cust) != NULL
-	      && startswith (COMPUNIT_PRODUCER (cust), "clang ")))
+	      && (startswith (COMPUNIT_PRODUCER (cust), "clang ")
+                  || startswith (COMPUNIT_PRODUCER (cust), " F90 Flang"))))
         return std::max (start_pc, post_prologue_pc);
     }
  
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index f0b7949fd6..9d6e42ad39 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-08-14  Alok Kumar Sharma  <AlokKumar.Sharma@amd.com>
+
+	* gdb.fortran/vla-type.exp: Skip commands not required for
+	the Flang compiled binaries after prologue fix.
+
 2020-08-16  Tom de Vries  <tdevries@suse.de>
 
 	PR gdb/25350
diff --git a/gdb/testsuite/gdb.fortran/vla-type.exp b/gdb/testsuite/gdb.fortran/vla-type.exp
index 925c583edc..e2b8d71b4c 100755
--- a/gdb/testsuite/gdb.fortran/vla-type.exp
+++ b/gdb/testsuite/gdb.fortran/vla-type.exp
@@ -33,8 +33,12 @@ set int [fortran_int4]
 
 # Check if not allocated VLA in type does not break
 # the debugger when accessing it.
-gdb_breakpoint [gdb_get_line_number "before-allocated"]
-gdb_continue_to_breakpoint "before-allocated"
+# break main for Flang compiler already breaks here
+if ![test_compiler_info "clang-*"] {
+    gdb_breakpoint [gdb_get_line_number "before-allocated"]
+    gdb_continue_to_breakpoint "before-allocated"
+}
+
 gdb_test "print twov" " = \\\( ivla1 = <not allocated>, ivla2 = <not allocated> \\\)" \
   "print twov before allocated"
 gdb_test "print twov%ivla1" " = <not allocated>" \
-- 
2.17.1