xtensa: Add support for sibling call optimization

This patch introduces support for sibling call optimization, when call0
ABI is in effect.

gcc/ChangeLog:

	* config/xtensa/xtensa-protos.h (xtensa_prepare_expand_call,
	xtensa_emit_sibcall): New prototypes.
	(xtensa_expand_epilogue): Add new argument that specifies whether
	or not sibling call.
	* config/xtensa/xtensa.cc (TARGET_FUNCTION_OK_FOR_SIBCALL):
	New macro definition.
	(xtensa_prepare_expand_call): New function in order to share
	the common code.
	(xtensa_emit_sibcall, xtensa_function_ok_for_sibcall):
	New functions.
	(xtensa_expand_epilogue): Add new argument sibcall_p and use it
	for sibling call handling.
	* config/xtensa/xtensa.md (call, call_value):
	Use xtensa_prepare_expand_call.
	(call_internal, call_value_internal):
	Add the condition in order to be disabled if sibling call.
	(sibcall, sibcall_value, sibcall_epilogue): New expansions.
	(sibcall_internal, sibcall_value_internal): New insn patterns,
	and split ones in order to take care of the indirect sibcalls.

gcc/testsuite/ChangeLog:

	* gcc.target/xtensa/sibcalls.c: New.

diff --git a/gcc/config/xtensa/xtensa-protos.h b/gcc/config/xtensa/xtensa-protos.h
index 168ad70710ba095a1075cf755973a3c35afeac58..e020a332b0376922de720e93d36e3a9e9442d5fb 100644 (file)
--- a/gcc/config/xtensa/xtensa-protos.h
+++ b/gcc/config/xtensa/xtensa-protos.h
@@ -53,7 +53,9 @@ extern void xtensa_expand_atomic (enum rtx_code, rtx, rtx, rtx, bool);
 extern void xtensa_emit_loop_end (rtx_insn *, rtx *);
 extern char *xtensa_emit_branch (bool, rtx *);
 extern char *xtensa_emit_movcc (bool, bool, bool, rtx *);
+extern void xtensa_prepare_expand_call (int, rtx *);
 extern char *xtensa_emit_call (int, rtx *);
+extern char *xtensa_emit_sibcall (int, rtx *);
 extern bool xtensa_tls_referenced_p (rtx);
 extern enum rtx_code xtensa_shlrd_which_direction (rtx, rtx);
 
@@ -73,7 +75,7 @@ extern int xtensa_dbx_register_number (int);
 extern long compute_frame_size (poly_int64);
 extern bool xtensa_use_return_instruction_p (void);
 extern void xtensa_expand_prologue (void);
-extern void xtensa_expand_epilogue (void);
+extern void xtensa_expand_epilogue (bool);
 extern void order_regs_for_local_alloc (void);
 extern enum reg_class xtensa_regno_to_class (int regno);
 extern HOST_WIDE_INT xtensa_initial_elimination_offset (int from, int to);

diff --git a/gcc/config/xtensa/xtensa.cc b/gcc/config/xtensa/xtensa.cc
index 58b6eb0b71118baf996becad58f673be8afaa4ba..d6f08b11648ca79008d815afd89f193585516558 100644 (file)
--- a/gcc/config/xtensa/xtensa.cc
+++ b/gcc/config/xtensa/xtensa.cc
@@ -189,7 +189,7 @@ static bool xtensa_can_eliminate (const int from ATTRIBUTE_UNUSED,
                                  const int to);
 static HOST_WIDE_INT xtensa_starting_frame_offset (void);
 static unsigned HOST_WIDE_INT xtensa_asan_shadow_offset (void);
-
+static bool xtensa_function_ok_for_sibcall (tree, tree);
 static rtx xtensa_delegitimize_address (rtx);
 
 \f
@@ -347,6 +347,9 @@ static rtx xtensa_delegitimize_address (rtx);
 #undef TARGET_DELEGITIMIZE_ADDRESS
 #define TARGET_DELEGITIMIZE_ADDRESS xtensa_delegitimize_address
 
+#undef TARGET_FUNCTION_OK_FOR_SIBCALL
+#define TARGET_FUNCTION_OK_FOR_SIBCALL xtensa_function_ok_for_sibcall
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 \f
@@ -2127,6 +2130,20 @@ xtensa_emit_movcc (bool inverted, bool isfp, bool isbool, rtx *operands)
 }
 
 
+void
+xtensa_prepare_expand_call (int callop, rtx *operands)
+{
+  rtx addr = XEXP (operands[callop], 0);
+
+  if (flag_pic && SYMBOL_REF_P (addr)
+      && (!SYMBOL_REF_LOCAL_P (addr) || SYMBOL_REF_EXTERNAL_P (addr)))
+    addr = gen_sym_PLT (addr);
+
+  if (!call_insn_operand (addr, VOIDmode))
+    XEXP (operands[callop], 0) = copy_to_mode_reg (Pmode, addr);
+}
+
+
 char *
 xtensa_emit_call (int callop, rtx *operands)
 {
@@ -2145,6 +2162,24 @@ xtensa_emit_call (int callop, rtx *operands)
 }
 
 
+char *
+xtensa_emit_sibcall (int callop, rtx *operands)
+{
+  static char result[64];
+  rtx tgt = operands[callop];
+
+  if (GET_CODE (tgt) == CONST_INT)
+    sprintf (result, "j.l\t" HOST_WIDE_INT_PRINT_HEX ", a9",
+            INTVAL (tgt));
+  else if (register_operand (tgt, VOIDmode))
+    sprintf (result, "jx\t%%%d", callop);
+  else
+    sprintf (result, "j.l\t%%%d, a9", callop);
+
+  return result;
+}
+
+
 bool
 xtensa_legitimate_address_p (machine_mode mode, rtx addr, bool strict)
 {
@@ -3270,7 +3305,7 @@ xtensa_expand_prologue (void)
 }
 
 void
-xtensa_expand_epilogue (void)
+xtensa_expand_epilogue (bool sibcall_p)
 {
   if (!TARGET_WINDOWED_ABI)
     {
@@ -3304,10 +3339,13 @@ xtensa_expand_epilogue (void)
          if (xtensa_call_save_reg(regno))
            {
              rtx x = gen_rtx_PLUS (Pmode, stack_pointer_rtx, GEN_INT (offset));
+             rtx reg;
 
              offset -= UNITS_PER_WORD;
-             emit_move_insn (gen_rtx_REG (SImode, regno),
+             emit_move_insn (reg = gen_rtx_REG (SImode, regno),
                              gen_frame_mem (SImode, x));
+             if (regno == A0_REG && sibcall_p)
+               emit_use (reg);
            }
        }
 
@@ -3342,7 +3380,8 @@ xtensa_expand_epilogue (void)
                                  EH_RETURN_STACKADJ_RTX));
     }
   cfun->machine->epilogue_done = true;
-  emit_jump_insn (gen_return ());
+  if (!sibcall_p)
+    emit_jump_insn (gen_return ());
 }
 
 bool
@@ -4869,6 +4908,17 @@ xtensa_asan_shadow_offset (void)
   return HOST_WIDE_INT_UC (0x10000000);
 }
 
+/* Implement TARGET_FUNCTION_OK_FOR_SIBCALL.  */
+static bool
+xtensa_function_ok_for_sibcall (tree decl ATTRIBUTE_UNUSED, tree exp ATTRIBUTE_UNUSED)
+{
+  /* Do not allow sibcalls when windowed registers ABI is in effect.  */
+  if (TARGET_WINDOWED_ABI)
+    return false;
+
+  return true;
+}
+
 static rtx
 xtensa_delegitimize_address (rtx op)
 {

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index 5d0f346b01a803d34773f3376e1398b982184b27..3b05166988fe850fc8c079c2ae322c1f1d6ec5b2 100644 (file)
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -25,6 +25,7 @@
   (A7_REG              7)
   (A8_REG              8)
   (A9_REG              9)
+  (A10_REG             10)
 
   (UNSPEC_NOP          2)
   (UNSPEC_PLT          3)
@@ -2148,18 +2149,13 @@
         (match_operand 1 "" ""))]
   ""
 {
-  rtx addr = XEXP (operands[0], 0);
-  if (flag_pic && GET_CODE (addr) == SYMBOL_REF
-      && (!SYMBOL_REF_LOCAL_P (addr) || SYMBOL_REF_EXTERNAL_P (addr)))
-    addr = gen_sym_PLT (addr);
-  if (!call_insn_operand (addr, VOIDmode))
-    XEXP (operands[0], 0) = copy_to_mode_reg (Pmode, addr);
+  xtensa_prepare_expand_call (0, operands);
 })
 
 (define_insn "call_internal"
   [(call (mem (match_operand:SI 0 "call_insn_operand" "nir"))
         (match_operand 1 "" "i"))]
-  ""
+  "!SIBLING_CALL_P (insn)"
 {
   return xtensa_emit_call (0, operands);
 }
@@ -2173,19 +2169,14 @@
              (match_operand 2 "" "")))]
   ""
 {
-  rtx addr = XEXP (operands[1], 0);
-  if (flag_pic && GET_CODE (addr) == SYMBOL_REF
-      && (!SYMBOL_REF_LOCAL_P (addr) || SYMBOL_REF_EXTERNAL_P (addr)))
-    addr = gen_sym_PLT (addr);
-  if (!call_insn_operand (addr, VOIDmode))
-    XEXP (operands[1], 0) = copy_to_mode_reg (Pmode, addr);
+  xtensa_prepare_expand_call (1, operands);
 })
 
 (define_insn "call_value_internal"
   [(set (match_operand 0 "register_operand" "=a")
         (call (mem (match_operand:SI 1 "call_insn_operand" "nir"))
               (match_operand 2 "" "i")))]
-  ""
+  "!SIBLING_CALL_P (insn)"
 {
   return xtensa_emit_call (1, operands);
 }
@@ -2193,6 +2184,70 @@
    (set_attr "mode"    "none")
    (set_attr "length"  "3")])
 
+(define_expand "sibcall"
+  [(call (match_operand 0 "memory_operand" "")
+        (match_operand 1 "" ""))]
+  "!TARGET_WINDOWED_ABI"
+{
+  xtensa_prepare_expand_call (0, operands);
+})
+
+(define_insn "sibcall_internal"
+  [(call (mem:SI (match_operand:SI 0 "call_insn_operand" "nir"))
+        (match_operand 1 "" "i"))]
+  "!TARGET_WINDOWED_ABI && SIBLING_CALL_P (insn)"
+{
+  return xtensa_emit_sibcall (0, operands);
+}
+  [(set_attr "type"    "call")
+   (set_attr "mode"    "none")
+   (set_attr "length"  "3")])
+
+(define_split
+  [(call (mem:SI (match_operand:SI 0 "register_operand"))
+        (match_operand 1 ""))]
+  "reload_completed
+   && !TARGET_WINDOWED_ABI && SIBLING_CALL_P (insn)
+   && IN_RANGE (REGNO (operands[0]), 12, 15)"
+  [(set (reg:SI A10_REG)
+       (match_dup 0))
+   (call (mem:SI (reg:SI A10_REG))
+        (match_dup 1))])
+
+(define_expand "sibcall_value"
+  [(set (match_operand 0 "register_operand" "")
+       (call (match_operand 1 "memory_operand" "")
+             (match_operand 2 "" "")))]
+  "!TARGET_WINDOWED_ABI"
+{
+  xtensa_prepare_expand_call (1, operands);
+})
+
+(define_insn "sibcall_value_internal"
+  [(set (match_operand 0 "register_operand" "=a")
+       (call (mem:SI (match_operand:SI 1 "call_insn_operand" "nir"))
+             (match_operand 2 "" "i")))]
+  "!TARGET_WINDOWED_ABI && SIBLING_CALL_P (insn)"
+{
+  return xtensa_emit_sibcall (1, operands);
+}
+  [(set_attr "type"    "call")
+   (set_attr "mode"    "none")
+   (set_attr "length"  "3")])
+
+(define_split
+  [(set (match_operand 0 "register_operand")
+       (call (mem:SI (match_operand:SI 1 "register_operand"))
+             (match_operand 2 "")))]
+  "reload_completed
+   && !TARGET_WINDOWED_ABI && SIBLING_CALL_P (insn)
+   && IN_RANGE (REGNO (operands[1]), 12, 15)"
+  [(set (reg:SI A10_REG)
+       (match_dup 1))
+   (set (match_dup 0)
+       (call (mem:SI (reg:SI A10_REG))
+             (match_dup 2)))])
+
 (define_insn "entry"
   [(set (reg:SI A1_REG)
        (unspec_volatile:SI [(match_operand:SI 0 "const_int_operand" "i")]
@@ -2260,7 +2315,15 @@
   [(return)]
   ""
 {
-  xtensa_expand_epilogue ();
+  xtensa_expand_epilogue (false);
+  DONE;
+})
+
+(define_expand "sibcall_epilogue"
+  [(return)]
+  "!TARGET_WINDOWED_ABI"
+{
+  xtensa_expand_epilogue (true);
   DONE;
 })
 

diff --git a/gcc/testsuite/gcc.target/xtensa/sibcalls.c b/gcc/testsuite/gcc.target/xtensa/sibcalls.c
new file mode 100644 (file)
index 0000000..d2b3fcc
--- /dev/null
+++ b/gcc/testsuite/gcc.target/xtensa/sibcalls.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mabi=call0 -foptimize-sibling-calls" } */
+
+extern int foo(int);
+extern void bar(int);
+
+int test_0(int a) {
+    return foo(a);
+}
+
+void test_1(int a) {
+    bar(a);
+}
+
+int test_2(int (*a)(void)) {
+    bar(0);
+    return a();
+}
+
+/* { dg-final { scan-assembler-not "ret" } } */