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Re: [PATCH][AARCH64] Support tail indirect function call


On 21/05/14 15:44, Marcus Shawcroft wrote:
Couple of comments:

+typedef void FP(int);

GNU style please, space before (.

+void f1(FP fp, int n) { (fp)(n); }

GNU style please, line breaks after void, '(' and ';'. Space between
')' an '('. Likewise in the following line.

We should really follow the test case name convention, see
https://gcc.gnu.org/wiki/TestCaseWriting, specifically paragraph 1.

+(define_register_constraint "Ucs" "CALLER_SAVE_REGS"
+ "@internal The caller save registers.  Useful for sibcalls.")

Please move this hunk up and place with the other
define_register_constraints.  Line break after @internal like the
other entries in this file  Drop the "Useful for ..." part of the
comment.

+   br\\t%0
+   b\\t%a0"
    [(set_attr "type" "branch")]

Don't forget to add another attribute value for the new alternative.
Likewise is the following pattern.

    CORE_REGS,
+  CALLER_SAVE_REGS,
    GENERAL_REGS,

Register classes should be ordered such that if class x is contained
in class y, class x has the lower number therefore CALLER_SAVE_REGS
should be above CORE_REG.

Cheers
/Marcus


thanks for review, all fixed.

below is the updated patch.  no regression and bootstrap OK on aarch64.

ok for trunk?

gcc/
* config/aarch64/predicates.md (aarch64_call_insn_operand): New predicate.
  * config/aarch64/constraints.md ("Ucs", "Usf"):  New constraints.
* config/aarch64/aarch64.md (*sibcall_insn, *sibcall_value_insn): Adjust for
  tailcalling through registers.
* config/aarch64/aarch64.h (enum reg_class): New caller save register class.
  (REG_CLASS_NAMES): Likewise.
  (REG_CLASS_CONTENTS): Likewise.
* config/aarch64/aarch64.c (aarch64_function_ok_for_sibcall): Allow tailcalling
  without decls.

gcc/testsuite
  gcc.target/aarch64/tail-indirect-call_1.c: New test.

--
Jiong
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 8655f04..b8ef9cb 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -1198,18 +1198,10 @@ aarch64_expand_mov_immediate (rtx dest, rtx imm)
 }
 
 static bool
-aarch64_function_ok_for_sibcall (tree decl, tree exp ATTRIBUTE_UNUSED)
+aarch64_function_ok_for_sibcall (tree decl ATTRIBUTE_UNUSED,
+				 tree exp ATTRIBUTE_UNUSED)
 {
-  /* Indirect calls are not currently supported.  */
-  if (decl == NULL)
-    return false;
-
-  /* Cannot tail-call to long-calls, since these are outside of the
-     range of a branch instruction (we could handle this if we added
-     support for indirect tail-calls.  */
-  if (aarch64_decl_is_long_call_p (decl))
-    return false;
-
+  /* Currently, always true.  */
   return true;
 }
 
@@ -4270,6 +4262,7 @@ aarch64_class_max_nregs (reg_class_t regclass, enum machine_mode mode)
 {
   switch (regclass)
     {
+    case CALLER_SAVE_REGS:
     case CORE_REGS:
     case POINTER_REGS:
     case GENERAL_REGS:
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index c9b30d0..fa78f23 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -408,6 +408,7 @@ extern unsigned long aarch64_tune_flags;
 enum reg_class
 {
   NO_REGS,
+  CALLER_SAVE_REGS,
   CORE_REGS,
   GENERAL_REGS,
   STACK_REG,
@@ -423,6 +424,7 @@ enum reg_class
 #define REG_CLASS_NAMES				\
 {						\
   "NO_REGS",					\
+  "CALLER_SAVE_REGS",				\
   "CORE_REGS",					\
   "GENERAL_REGS",				\
   "STACK_REG",					\
@@ -435,6 +437,7 @@ enum reg_class
 #define REG_CLASS_CONTENTS						\
 {									\
   { 0x00000000, 0x00000000, 0x00000000 },	/* NO_REGS */		\
+  { 0x0007ffff, 0x00000000, 0x00000000 },	/* CALLER_SAVE_REGS */	\
   { 0x7fffffff, 0x00000000, 0x00000003 },	/* CORE_REGS */		\
   { 0x7fffffff, 0x00000000, 0x00000003 },	/* GENERAL_REGS */	\
   { 0x80000000, 0x00000000, 0x00000000 },	/* STACK_REG */		\
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 266d787..7c374b9 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -519,6 +519,10 @@
 	      (use (match_operand 2 "" ""))])]
   ""
   {
+    if (!REG_P (XEXP (operands[0], 0))
+       && (GET_CODE (XEXP (operands[0], 0)) != SYMBOL_REF))
+     XEXP (operands[0], 0) = force_reg (Pmode, XEXP (operands[0], 0));
+
     if (operands[2] == NULL_RTX)
       operands[2] = const0_rtx;
   }
@@ -532,31 +536,38 @@
 	      (use (match_operand 3 "" ""))])]
   ""
   {
+    if (!REG_P (XEXP (operands[1], 0))
+       && (GET_CODE (XEXP (operands[1], 0)) != SYMBOL_REF))
+     XEXP (operands[1], 0) = force_reg (Pmode, XEXP (operands[1], 0));
+
     if (operands[3] == NULL_RTX)
       operands[3] = const0_rtx;
   }
 )
 
 (define_insn "*sibcall_insn"
-  [(call (mem:DI (match_operand:DI 0 "" "X"))
+  [(call (mem:DI (match_operand:DI 0 "aarch64_call_insn_operand" "Ucs, Usf"))
 	 (match_operand 1 "" ""))
    (return)
    (use (match_operand 2 "" ""))]
-  "GET_CODE (operands[0]) == SYMBOL_REF"
-  "b\\t%a0"
-  [(set_attr "type" "branch")]
-
+  "SIBLING_CALL_P (insn)"
+  "@
+   br\\t%0
+   b\\t%a0"
+  [(set_attr "type" "branch, branch")]
 )
 
 (define_insn "*sibcall_value_insn"
   [(set (match_operand 0 "" "")
-	(call (mem:DI (match_operand 1 "" "X"))
+	(call (mem:DI (match_operand 1 "aarch64_call_insn_operand" "Ucs, Usf"))
 	      (match_operand 2 "" "")))
    (return)
    (use (match_operand 3 "" ""))]
-  "GET_CODE (operands[1]) == SYMBOL_REF"
-  "b\\t%a1"
-  [(set_attr "type" "branch")]
+  "SIBLING_CALL_P (insn)"
+  "@
+   br\\t%1
+   b\\t%a1"
+  [(set_attr "type" "branch, branch")]
 )
 
 ;; Call subroutine returning any type.
diff --git a/gcc/config/aarch64/constraints.md b/gcc/config/aarch64/constraints.md
index 12ab570..807d0b1 100644
--- a/gcc/config/aarch64/constraints.md
+++ b/gcc/config/aarch64/constraints.md
@@ -21,6 +21,9 @@
 (define_register_constraint "k" "STACK_REG"
   "@internal The stack register.")
 
+(define_register_constraint "Ucs" "CALLER_SAVE_REGS"
+  "@internal The caller save registers.")
+
 (define_register_constraint "w" "FP_REGS"
   "Floating point and SIMD vector registers.")
 
@@ -92,6 +95,10 @@
   (and (match_code "const_int")
        (match_test "(unsigned HOST_WIDE_INT) ival < 64")))
 
+(define_constraint "Usf"
+  "@internal Usf is a symbol reference."
+  (match_code "symbol_ref"))
+
 (define_constraint "UsM"
   "@internal
   A constraint that matches the immediate constant -1."
diff --git a/gcc/config/aarch64/predicates.md b/gcc/config/aarch64/predicates.md
index c8e27d8..2702a3c 100644
--- a/gcc/config/aarch64/predicates.md
+++ b/gcc/config/aarch64/predicates.md
@@ -26,6 +26,10 @@
 			      && GET_MODE_CLASS (GET_MODE (op)) == MODE_CC"))))
 )
 
+(define_predicate "aarch64_call_insn_operand"
+  (ior (match_code "symbol_ref")
+       (match_operand 0 "register_operand")))
+
 (define_predicate "aarch64_simd_register"
   (and (match_code "reg")
        (ior (match_test "REGNO_REG_CLASS (REGNO (op)) == FP_LO_REGS")
diff --git a/gcc/testsuite/gcc.target/aarch64/tail-indirect-call_1.c b/gcc/testsuite/gcc.target/aarch64/tail-indirect-call_1.c
new file mode 100644
index 0000000..4759d20
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/tail-indirect-call_1.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+typedef void FP (int);
+
+/* { dg-final { scan-assembler "br" } } */
+/* { dg-final { scan-assembler-not "blr" } } */
+void
+f1 (FP fp, int n)
+{
+  (fp) (n);
+}
+
+void
+f2 (int n, FP fp)
+{
+  (fp) (n);
+}

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