Add support for -membedded-pic

From-SVN: r6997

gcc/config/mips/mips.c

@@ -3191,6 +3191,28 @@ override_options ()
   else
     mips_abicalls = MIPS_ABICALLS_NO;
 
+  /* -membedded-pic is a form of PIC code suitable for embedded
+     systems.  All calls are made using PC relative addressing, and
+     all data is addressed using the $gp register.  This requires gas,
+     which does most of the work, and GNU ld, which automatically
+     expands PC relative calls which are out of range into a longer
+     instruction sequence.  All gcc really does differently is
+     generate a different sequence for a switch.  */
+  if (TARGET_EMBEDDED_PIC)
+    {
+      flag_pic = 1;
+      if (TARGET_ABICALLS)
+	warning ("-membedded-pic and -mabicalls are incompatible");
+      if (g_switch_set)
+	warning ("-G and -membedded-pic are incompatible");
+      /* Setting mips_section_threshold is not required, because gas
+	 will force everything to be GP addressable anyhow, but
+	 setting it will cause gcc to make better estimates of the
+	 number of instructions required to access a particular data
+	 item.  */
+      mips_section_threshold = 0x7fffffff;
+    }
+
   /* -mrnames says to use the MIPS software convention for register
      names instead of the hardware names (ie, $a0 instead of $4).
      We do this by switching the names in mips_reg_names, which the
@@ -3387,6 +3409,7 @@ mips_debugger_offset (addr, offset)
    'M'  print high-order register of double-word register operand.
    'C'  print part of opcode for a branch condition.
    'N'  print part of opcode for a branch condition, inverted.
+   'S'  X is CODE_LABEL, print with prefix of "LS" (for embedded switch).
    '('	Turn on .set noreorder
    ')'	Turn on .set reorder
    '['	Turn on .set noat
@@ -3569,6 +3592,14 @@ print_operand (file, op, letter)
 	abort_with_insn (op, "PRINT_OPERAND, illegal insn for %%N");
       }
 
+  else if (letter == 'S')
+    {
+      char buffer[100];
+
+      ASM_GENERATE_INTERNAL_LABEL (buffer, "LS", CODE_LABEL_NUMBER (op));
+      assemble_name (file, buffer);
+    }
+
   else if (code == REG)
     {
       register int regnum = REGNO (op);

gcc/config/mips/mips.h

@@ -254,12 +254,12 @@ extern char	       *mktemp ();
 #define MASK_HALF_PIC	0x00000800	/* Emit OSF-style pic refs to externs*/
 #define MASK_LONG_CALLS	0x00001000	/* Always call through a register */
 #define MASK_64BIT	0x00002000	/* Use 64 bit GP registers and insns */
-#define MASK_UNUSED1	0x00004000
-#define MASK_UNUSED2	0x00008000
-#define MASK_UNUSED3	0x00010000
-#define MASK_UNUSED4	0x00020000
-#define MASK_UNUSED5	0x00040000
-#define MASK_UNUSED6	0x00080000
+#define MASK_EMBEDDED_PIC 0x00004000	/* Generate embedded PIC code */
+#define MASK_UNUSED1	0x00008000
+#define MASK_UNUSED2	0x00010000
+#define MASK_UNUSED3	0x00020000
+#define MASK_UNUSED4	0x00040000
+#define MASK_UNUSED5	0x00080000
 
 					/* Dummy switches used only in spec's*/
 #define MASK_MIPS_TFILE	0x00000000	/* flag for mips-tfile usage */
@@ -327,6 +327,10 @@ extern char	       *mktemp ();
 					/* always call through a register */
 #define TARGET_LONG_CALLS	(target_flags & MASK_LONG_CALLS)
 
+					/* generate embedded PIC code;
+					   requires gas.  */
+#define TARGET_EMBEDDED_PIC	(target_flags & MASK_EMBEDDED_PIC)
+
 /* Macro to define tables used to set the flags.
    This is a list in braces of pairs in braces,
    each pair being { "NAME", VALUE }
@@ -364,6 +368,8 @@ extern char	       *mktemp ();
   {"no-half-pic",	 -MASK_HALF_PIC},				\
   {"long-calls",	  MASK_LONG_CALLS},				\
   {"no-long-calls",	 -MASK_LONG_CALLS},				\
+  {"embedded-pic",	  MASK_EMBEDDED_PIC},				\
+  {"no-embedded-pic",	 -MASK_EMBEDDED_PIC},				\
   {"debug",		  MASK_DEBUG},					\
   {"debuga",		  MASK_DEBUG_A},				\
   {"debugb",		  MASK_DEBUG_B},				\
@@ -552,7 +558,8 @@ while (0)
 %{ggdb:-g} %{ggdb0:-g0} %{ggdb1:-g1} %{ggdb2:-g2} %{ggdb3:-g3} \
 %{gstabs:-g} %{gstabs0:-g0} %{gstabs1:-g1} %{gstabs2:-g2} %{gstabs3:-g3} \
 %{gstabs+:-g} %{gstabs+0:-g0} %{gstabs+1:-g1} %{gstabs+2:-g2} %{gstabs+3:-g3} \
-%{gcoff:-g} %{gcoff0:-g0} %{gcoff1:-g1} %{gcoff2:-g2} %{gcoff3:-g3}"
+%{gcoff:-g} %{gcoff0:-g0} %{gcoff1:-g1} %{gcoff2:-g2} %{gcoff3:-g3} \
+%{membedded-pic}"
 
 #else
 /* not GAS */
@@ -568,7 +575,8 @@ while (0)
 %{ggdb:-g} %{ggdb0:-g0} %{ggdb1:-g1} %{ggdb2:-g2} %{ggdb3:-g3} \
 %{gstabs:-g} %{gstabs0:-g0} %{gstabs1:-g1} %{gstabs2:-g2} %{gstabs3:-g3} \
 %{gstabs+:-g} %{gstabs+0:-g0} %{gstabs+1:-g1} %{gstabs+2:-g2} %{gstabs+3:-g3} \
-%{gcoff:-g} %{gcoff0:-g0} %{gcoff1:-g1} %{gcoff2:-g2} %{gcoff3:-g3}"
+%{gcoff:-g} %{gcoff0:-g0} %{gcoff1:-g1} %{gcoff2:-g2} %{gcoff3:-g3} \
+%{membedded-pic}"
 
 #endif
 #endif	/* ASM_SPEC */
@@ -3375,12 +3383,33 @@ do {									\
 	   VALUE)
 
 /* This is how to output an element of a case-vector that is relative.
-   This is used for pc-relative code (e.g. when TARGET_ABICALLS).  */
+   This is used for pc-relative code (e.g. when TARGET_ABICALLS or
+   TARGET_EMBEDDED_PIC).  */
 
 #define ASM_OUTPUT_ADDR_DIFF_ELT(STREAM, VALUE, REL)			\
-  fprintf (STREAM, "\t%s\t$L%d\n",					\
-	   TARGET_LONG64 ? ".gpdword" : ".gpword",			\
-	   VALUE)
+do {									\
+  if (TARGET_EMBEDDED_PIC)						\
+    fprintf (STREAM, "\t%s\t$L%d-$LS%d\n",				\
+	     TARGET_LONG64 ? ".dword" : ".word",			\
+	     VALUE, REL);						\
+  else									\
+    fprintf (STREAM, "\t%s\t$L%d\n",					\
+	     TARGET_LONG64 ? ".gpdword" : ".gpword",			\
+	     VALUE);							\
+} while (0)
+
+/* When generating embedded PIC code we want to put the jump table in
+   the .text section.  In all other cases, we want to put the jump
+   table in the .rdata section.  Unfortunately, we can't use
+   JUMP_TABLES_IN_TEXT_SECTION, because it is not conditional.
+   Instead, we use ASM_OUTPUT_CASE_LABEL to switch back to the .text
+   section if appropriate.  */
+#define ASM_OUTPUT_CASE_LABEL(FILE, PREFIX, NUM, INSN)			\
+do {									\
+  if (TARGET_EMBEDDED_PIC)						\
+    text_section ();							\
+  ASM_OUTPUT_INTERNAL_LABEL (FILE, PREFIX, NUM);			\
+} while (0)
 
 /* This is how to output an assembler line
    that says to advance the location counter

gcc/config/mips/mips.md

@@ -5410,6 +5410,90 @@ move\\t%0,%z4\\n\\
    (set_attr "mode"	"none")
    (set_attr "length"	"1")])
 
+;; Implement a switch statement when generating embedded PIC code.
+;; Switches are implemented by `tablejump' when not using -membedded-pic.
+
+(define_expand "casesi"
+  [(set (match_dup 5)
+	(minus:SI (match_operand:SI 0 "register_operand" "d")
+		  (match_operand:SI 1 "arith_operand" "dI")))
+   (set (cc0)
+	(compare:CC (match_dup 5)
+		    (match_operand:SI 2 "arith_operand" "")))
+   (set (pc)
+	(if_then_else (gtu (cc0)
+			   (const_int 0))
+		      (label_ref (match_operand 4 "" ""))
+		      (pc)))
+   (parallel
+    [(set (pc)
+	  (mem:SI (plus:SI (mult:SI (match_dup 5)
+				    (const_int 4))
+			   (label_ref (match_operand 3 "" "")))))
+     (clobber (match_scratch:SI 6 ""))
+     (clobber (reg:SI 31))])]
+  "TARGET_EMBEDDED_PIC"
+  "
+{
+  /* We need slightly different code for eight byte table entries.  */
+  if (TARGET_LONG64)
+    abort ();
+
+  if (operands[0])
+    {
+      rtx reg = gen_reg_rtx (SImode);
+
+      /* The constraints should handle this, but they don't.  */
+      operands[0] = force_reg (SImode, operands[0]);
+      if (! arith_operand (operands[1]))
+	operands[1] = force_reg (SImode, operands[1]);
+      if (! arith_operand (operands[2]))
+	operands[2] = force_reg (SImode, operands[2]);
+
+      /* If the index is too large, go to the default label.  */
+      emit_insn (gen_subsi3 (reg, operands[0], operands[1]));
+      emit_insn (gen_cmpsi (reg, operands[2]));
+      emit_insn (gen_bgtu (operands[4]));
+
+      /* Do the PIC jump.  */
+      emit_insn (gen_casesi_internal (reg, operands[3], gen_reg_rtx (SImode)));
+
+      DONE;
+    }
+}")
+
+;; An embedded PIC switch statement looks like this:
+;;	bal	$LS1
+;;	sll	$reg,$index,2
+;; $LS1:
+;;	addu	$reg,$reg,$31
+;;	lw	$reg,$L1-$LS1($reg)
+;;	addu	$reg,$reg,$31
+;;	j	$reg
+;; $L1:
+;;	.word	case1-$LS1
+;;	.word	case2-$LS1
+;;	...
+
+(define_insn "casesi_internal"
+  [(set (pc)
+	(mem:SI (plus:SI (mult:SI (match_operand:SI 0 "register_operand" "d")
+				  (const_int 4))
+			 (label_ref (match_operand 1 "" "")))))
+   (clobber (match_operand:SI 2 "register_operand" "d"))
+   (clobber (reg:SI 31))]
+  "TARGET_EMBEDDED_PIC"
+  "*
+{
+  output_asm_insn (\"%(bal\\t%S1\;sll\\t%0,2\\n%S1:\", operands);
+  output_asm_insn (\"addu\\t%0,%0,$31%)\", operands);
+  output_asm_insn (\"lw\\t%0,%1-%S1(%0)\;addu\\t%0,%0,$31\", operands);
+  return \"j\\t%0\";
+}"
+  [(set_attr "type"	"jump")
+   (set_attr "mode"	"none")
+   (set_attr "length"	"6")])
+
 
 ;;
 ;;  ....................