mips.c (override_options): Set MASK_BRANCHLIKELY in target_flags based on ISA...

2002-08-06  Chris Demetriou  <cgd@broadcom.com>

        * config/mips/mips.c (override_options): Set MASK_BRANCHLIKELY
        in target_flags based on ISA, if it was not set on the command
        line.  Warn if MASK_BRANCHLIKLEY is set but the ISA does not
        support Branch Likely instructions.
        * config/mips/mips.h (MASK_BRANCHLIKLEY): New macro.
        (TARGET_BRANCHLIKELY): Likewise.
        (TARGET_SWITCHES): Add -mbranch-likely and -mno-branch-likely.
        (GENERATE_BRANCHLIKELY): Use TARGET_BRANCHLIKELY rather than
        ISA_HAS_BRANCHLIKELY.
        (ISA_HAS_BRANCHLIKELY): Do not include MIPS16 check.
        * doc/invoke.texi: Document new MIPS -mbranch-likely and
        -mno-branch-likely options.

From-SVN: r56088

2 files changed, 35 insertions, 3 deletions

diff --git a/gcc/config/mips/mips.c b/gcc/config/mips/mips.c
index 31cd0d0..aa6be83 100644
--- a/gcc/config/mips/mips.c
+++ b/gcc/config/mips/mips.c
@@ -5177,6 +5177,31 @@ override_options ()
   if (mips_abi != ABI_32 && mips_abi != ABI_O64)
     flag_pcc_struct_return = 0;
 
+  if ((target_flags_explicit & MASK_BRANCHLIKELY) == 0)
+    {
+      /* If neither -mbranch-likely nor -mno-branch-likely was given
+	 on the command line, set MASK_BRANCHLIKELY based on the target
+	 architecture.
+
+	 By default, we enable use of Branch Likely instructions on
+	 all architectures which support them except for MIPS32 and MIPS64
+	 (i.e., the generic MIPS32 and MIPS64 ISAs, and processors which
+	 implement them).
+
+	 The MIPS32 and MIPS64 architecture specifications say "Software
+	 is strongly encouraged to avoid use of Branch Likely
+	 instructions, as they will be removed from a future revision
+	 of the [MIPS32 and MIPS64] architecture."  Therefore, we do not
+	 issue those instructions unless instructed to do so by
+	 -mbranch-likely.  */
+      if (ISA_HAS_BRANCHLIKELY && !(ISA_MIPS32 || ISA_MIPS64))
+	target_flags |= MASK_BRANCHLIKELY;
+      else
+	target_flags &= ~MASK_BRANCHLIKELY;
+    }
+  if (TARGET_BRANCHLIKELY && !ISA_HAS_BRANCHLIKELY)
+    warning ("generation of Branch Likely instructions enabled, but not supported by architecture");
+
   /* -fpic (-KPIC) is the default when TARGET_ABICALLS is defined.  We need
      to set flag_pic so that the LEGITIMATE_PIC_OPERAND_P macro will work.  */
   /* ??? -non_shared turns off pic code generation, but this is not
diff --git a/gcc/config/mips/mips.h b/gcc/config/mips/mips.h
index 7db4f9e..eaf6852 100644
--- a/gcc/config/mips/mips.h
+++ b/gcc/config/mips/mips.h
@@ -232,6 +232,8 @@ extern void		sbss_section PARAMS ((void));
 					   consts in rodata */
 #define MASK_NO_FUSED_MADD 0x01000000   /* Don't generate floating point
 					   multiply-add operations.  */
+#define MASK_BRANCHLIKELY  0x02000000   /* Generate Branch Likely
+					   instructions.  */
 
 					/* Debug switches, not documented */
 #define MASK_DEBUG	0		/* unused */
@@ -322,6 +324,8 @@ extern void		sbss_section PARAMS ((void));
 #define TARGET_NO_CHECK_ZERO_DIV (target_flags & MASK_NO_CHECK_ZERO_DIV)
 #define TARGET_CHECK_RANGE_DIV  (target_flags & MASK_CHECK_RANGE_DIV)
 
+#define TARGET_BRANCHLIKELY	(target_flags & MASK_BRANCHLIKELY)
+
 /* This is true if we must enable the assembly language file switching
    code.  */
 
@@ -608,6 +612,10 @@ extern void		sbss_section PARAMS ((void));
      N_("Trap on integer divide overflow")},				\
   {"no-check-range-division",-MASK_CHECK_RANGE_DIV,			\
      N_("Don't trap on integer divide overflow")},			\
+  { "branch-likely",      MASK_BRANCHLIKELY,				\
+      N_("Use Branch Likely instructions, overriding default for arch")}, \
+  { "no-branch-likely",  -MASK_BRANCHLIKELY,				\
+      N_("Don't use Branch Likely instructions, overriding default for arch")}, \
   {"debug",		  MASK_DEBUG,					\
      NULL},								\
   {"debuga",		  MASK_DEBUG_A,					\
@@ -741,7 +749,7 @@ extern void		sbss_section PARAMS ((void));
 /* This is meant to be redefined in the host dependent files.  */
 #define SUBTARGET_TARGET_OPTIONS
 
-#define GENERATE_BRANCHLIKELY   (!TARGET_MIPS16 && ISA_HAS_BRANCHLIKELY)
+#define GENERATE_BRANCHLIKELY   (TARGET_BRANCHLIKELY && !TARGET_MIPS16)
 
 /* Generate three-operand multiply instructions for SImode.  */
 #define GENERATE_MULT3_SI       ((TARGET_MIPS3900                       \
@@ -776,8 +784,7 @@ extern void		sbss_section PARAMS ((void));
 /* ISA has branch likely instructions (eg. mips2).  */
 /* Disable branchlikely for tx39 until compare rewrite.  They haven't
    been generated up to this point.  */
-#define ISA_HAS_BRANCHLIKELY	(!ISA_MIPS1				\
-				 && !TARGET_MIPS16)
+#define ISA_HAS_BRANCHLIKELY	(!ISA_MIPS1)
 
 /* ISA has the conditional move instructions introduced in mips4.  */
 #define ISA_HAS_CONDMOVE        ((ISA_MIPS4				\