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[RFC][PR89245] Check REG_CALL_DECL note during the tail-merging


From: "Dragan Mladjenovic" <dmladjenovic@wavecomp.com>

This patch prevents merging of CALL instructions that that have different
REG_CALL_DECL notes attached to them.

On most architectures this is not an important distinction. Usually instruction patterns
for calls to different functions reference different SYMBOL_REF-s, so they won't match.
On MIPS PIC calls get split into an got_load/*call_internal pair where the latter represents
indirect register call w/o SYMBOL_REF attached (until machine_reorg pass). The bugzilla issue
had such two internal_call-s merged despite the fact that they had different register usage
information assigned by ipa-ra.

The check could be improved by checking if ipa-ra has actually assigned two different
register sets for two functions involved, but I chose to only do a quick rtx_equal check.

gcc/ChangeLog:

2019-07-07  Dragan Mladjenovic  <dmladjenovic@wavecomp.com>

	* cfgcleanup.c (old_insns_match_p): Check for equal REG_CALL_DECL notes
        on call instructions.

gcc/testsuite/ChangeLog:

2019-07-07  Dragan Mladjenovic  <dmladjenovic@wavecomp.com>

	* gcc.target/mips/cfgcleanup-jalr.c: New test.
---
 gcc/cfgcleanup.c                                |  9 +++++++++
 gcc/testsuite/gcc.target/mips/cfgcleanup-jalr.c | 17 +++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/mips/cfgcleanup-jalr.c

diff --git a/gcc/cfgcleanup.c b/gcc/cfgcleanup.c
index 992912c..9903249 100644
--- a/gcc/cfgcleanup.c
+++ b/gcc/cfgcleanup.c
@@ -1224,6 +1224,15 @@ old_insns_match_p (int mode ATTRIBUTE_UNUSED, rtx_insn *i1, rtx_insn *i2)
 		}
 	    }
 	}
+
+      n1 = find_reg_note (i1, REG_CALL_DECL, 0);
+      n2 = find_reg_note (i2, REG_CALL_DECL, 0);
+
+      if (!n1 && n2)
+        return dir_none;
+
+      if (n1 && (!n2 || !rtx_equal_p (XEXP (n1, 0), XEXP (n2, 0))))
+        return dir_none;
     }
 
   /* If both i1 and i2 are frame related, verify all the CFA notes
diff --git a/gcc/testsuite/gcc.target/mips/cfgcleanup-jalr.c b/gcc/testsuite/gcc.target/mips/cfgcleanup-jalr.c
new file mode 100644
index 0000000..a4c0c47
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/cfgcleanup-jalr.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-mabicalls -fpic" } */
+
+extern void foo (void*);
+
+extern void bar (void*);
+
+void test (void* p)
+{
+   if (!p)
+	foo(p);
+   else
+	bar(p);
+}
+
+/* { dg-final { scan-assembler "\\\.reloc\t1f,R_MIPS_JALR,foo" } } */
+/* { dg-final { scan-assembler "\\\.reloc\t1f,R_MIPS_JALR,bar" } } */
-- 
1.9.1


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