* config/i386/i386-protos.h (ix86_expand_compare): Add extern decl.

	* config/i386/i386.c (ix86_expand_compare): Remove `static'.
	* config/i386/i386.md (trap, conditional_trap): New insn & expand.


git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@36019 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 49 insertions, 0 deletions

diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index cada4dfcf56..7d4faf347cb 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -11129,3 +11129,52 @@
     return \"call\\t%*%1\";
 }"
   [(set_attr "type" "callv")])
+
+(define_insn "trap"
+  [(trap_if (const_int 1) (const_int 5))]
+  ""
+  "int\\t$5")
+
+;;; ix86 doesn't have conditional trap instructions, but we fake them
+;;; for the sake of bounds checking.  By emitting bounds checks as
+;;; conditional traps rather than as conditional jumps around
+;;; unconditional traps we avoid introducing spurious basic-block
+;;; boundaries and facilitate elimination of redundant checks.  In
+;;; honor of the too-inflexible-for-BPs `bound' instruction, we use
+;;; interrupt 5.
+;;; 
+;;; FIXME: Static branch prediction rules for ix86 are such that
+;;; forward conditional branches predict as untaken.  As implemented
+;;; below, pseudo conditional traps violate that rule.  We should use
+;;; .pushsection/.popsection to place all of the `int 5's in a special
+;;; section loaded at the end of the text segment and branch forward
+;;; there on bounds-failure, and then jump back immediately (in case
+;;; the system chooses to ignore bounds violations, or to report
+;;; violations and continue execution).
+
+(define_expand "conditional_trap"
+  [(trap_if (match_operator 0 "comparison_operator"
+	     [(match_dup 2) (const_int 0)])
+	    (match_operand 1 "const_int_operand" ""))]
+  ""
+  "
+{
+  emit_insn (gen_rtx_TRAP_IF (VOIDmode,
+			      ix86_expand_compare (GET_CODE (operands[0])),
+			      operands[1]));
+  DONE;
+}")
+
+(define_insn ""
+  [(trap_if (match_operator 0 "comparison_operator"
+	     [(reg 17) (const_int 0)])
+	    (match_operand 1 "const_int_operand" ""))]
+  ""
+  "*
+{
+  operands[2] = gen_label_rtx ();
+  output_asm_insn (\"j%c0\\t%l2\; int\\t%1\", operands);
+  ASM_OUTPUT_INTERNAL_LABEL (asm_out_file, \"L\",
+			     CODE_LABEL_NUMBER (operands[2]));
+  RET;
+}")