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re PR rtl-optimization/10817 (gcc does not optimize result=0;if(t!=0)result=t; to result=t;)
PR optimization/10817 * ifcvt.c (noce_emit_move_insn): Improve documentation comment. (noce_try_move): New function to optimize an if-the-else into an unconditional move, i.e. "if (a!=b) x=a; else x=b" into "x=a". (noce_process_if_block): Attempt simplification with noce_try_move. * simplify-rtx.c (simplify_ternary_operation): Some minor fixes and improvements to the optimizations of IF_THEN_ELSE expressions. (simplify_subreg): Silence signed/unsigned comparison warning. * gcc.c-torture/compile/20031102-1.c: New test case. From-SVN: r73200
This commit is contained in:
Roger Sayle
Roger Sayle
parent
2077750a86
commit
31f0f571e6
@ -1,3 +1,15 @@
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2003-11-02 Roger Sayle <roger@eyesopen.com>
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PR optimization/10817
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* ifcvt.c (noce_emit_move_insn): Improve documentation comment.
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(noce_try_move): New function to optimize an if-the-else into an
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unconditional move, i.e. "if (a!=b) x=a; else x=b" into "x=a".
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(noce_process_if_block): Attempt simplification with noce_try_move.
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* simplify-rtx.c (simplify_ternary_operation): Some minor fixes
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and improvements to the optimizations of IF_THEN_ELSE expressions.
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(simplify_subreg): Silence signed/unsigned comparison warning.
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2003-11-02 Richard Sandiford <rsandifo@redhat.com>
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* Makefile.in (targhooks.o, reload.o): Update dependencies.
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50
gcc/ifcvt.c
50
gcc/ifcvt.c
@ -602,6 +602,7 @@ struct noce_if_info
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};
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static rtx noce_emit_store_flag (struct noce_if_info *, rtx, int, int);
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static int noce_try_move (struct noce_if_info *);
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static int noce_try_store_flag (struct noce_if_info *);
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static int noce_try_addcc (struct noce_if_info *);
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static int noce_try_store_flag_constants (struct noce_if_info *);
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@ -674,7 +675,9 @@ noce_emit_store_flag (struct noce_if_info *if_info, rtx x, int reversep,
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|| code == GEU || code == GTU), normalize);
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}
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/* Emit instruction to move an rtx into STRICT_LOW_PART. */
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/* Emit instruction to move an rtx, possibly into STRICT_LOW_PART.
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X is the destination/target and Y is the value to copy. */
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static void
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noce_emit_move_insn (rtx x, rtx y)
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{
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@ -697,6 +700,49 @@ noce_emit_move_insn (rtx x, rtx y)
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GET_MODE_BITSIZE (inmode));
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}
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/* Convert "if (a != b) x = a; else x = b" into "x = a" and
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"if (a == b) x = a; else x = b" into "x = b". */
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static int
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noce_try_move (struct noce_if_info *if_info)
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{
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rtx cond = if_info->cond;
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enum rtx_code code = GET_CODE (cond);
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rtx y, seq;
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if (code != NE && code != EQ)
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return FALSE;
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/* This optimization isn't valid if either A or B could be a NaN
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or a signed zero. */
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if (HONOR_NANS (GET_MODE (if_info->x))
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|| HONOR_SIGNED_ZEROS (GET_MODE (if_info->x)))
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return FALSE;
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/* Check whether the operands of the comparison are A and in
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either order. */
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if ((rtx_equal_p (if_info->a, XEXP (cond, 0))
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&& rtx_equal_p (if_info->b, XEXP (cond, 1)))
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|| (rtx_equal_p (if_info->a, XEXP (cond, 1))
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&& rtx_equal_p (if_info->b, XEXP (cond, 0))))
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{
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y = (code == EQ) ? if_info->a : if_info->b;
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/* Avoid generating the move if the source is the destination. */
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if (! rtx_equal_p (if_info->x, y))
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{
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start_sequence ();
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noce_emit_move_insn (if_info->x, y);
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seq = get_insns ();
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end_sequence ();
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emit_insn_before_setloc (seq, if_info->jump,
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INSN_LOCATOR (if_info->insn_a));
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}
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return TRUE;
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}
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return FALSE;
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}
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/* Convert "if (test) x = 1; else x = 0".
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Only try 0 and STORE_FLAG_VALUE here. Other combinations will be
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@ -1894,6 +1940,8 @@ noce_process_if_block (struct ce_if_block * ce_info)
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goto success;
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}
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if (noce_try_move (&if_info))
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goto success;
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if (noce_try_store_flag (&if_info))
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goto success;
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if (noce_try_minmax (&if_info))
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@ -2821,18 +2821,33 @@ simplify_ternary_operation (enum rtx_code code, enum machine_mode mode,
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if (GET_CODE (op0) == CONST_INT)
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return op0 != const0_rtx ? op1 : op2;
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/* Convert a == b ? b : a to "a". */
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if (GET_CODE (op0) == NE && ! side_effects_p (op0)
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&& !HONOR_NANS (mode)
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&& rtx_equal_p (XEXP (op0, 0), op1)
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&& rtx_equal_p (XEXP (op0, 1), op2))
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/* Convert c ? a : a into "a". */
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if (rtx_equal_p (op1, op2) && ! side_effects_p (op0))
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return op1;
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else if (GET_CODE (op0) == EQ && ! side_effects_p (op0)
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&& !HONOR_NANS (mode)
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&& rtx_equal_p (XEXP (op0, 1), op1)
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&& rtx_equal_p (XEXP (op0, 0), op2))
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/* Convert a != b ? a : b into "a". */
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if (GET_CODE (op0) == NE
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&& ! side_effects_p (op0)
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&& ! HONOR_NANS (mode)
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&& ! HONOR_SIGNED_ZEROS (mode)
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&& ((rtx_equal_p (XEXP (op0, 0), op1)
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&& rtx_equal_p (XEXP (op0, 1), op2))
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|| (rtx_equal_p (XEXP (op0, 0), op2)
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&& rtx_equal_p (XEXP (op0, 1), op1))))
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return op1;
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/* Convert a == b ? a : b into "b". */
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if (GET_CODE (op0) == EQ
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&& ! side_effects_p (op0)
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&& ! HONOR_NANS (mode)
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&& ! HONOR_SIGNED_ZEROS (mode)
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&& ((rtx_equal_p (XEXP (op0, 0), op1)
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&& rtx_equal_p (XEXP (op0, 1), op2))
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|| (rtx_equal_p (XEXP (op0, 0), op2)
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&& rtx_equal_p (XEXP (op0, 1), op1))))
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return op2;
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else if (GET_RTX_CLASS (GET_CODE (op0)) == '<' && ! side_effects_p (op0))
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if (GET_RTX_CLASS (GET_CODE (op0)) == '<' && ! side_effects_p (op0))
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{
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enum machine_mode cmp_mode = (GET_MODE (XEXP (op0, 0)) == VOIDmode
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? GET_MODE (XEXP (op0, 1))
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@ -2874,6 +2889,7 @@ simplify_ternary_operation (enum rtx_code code, enum machine_mode mode,
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}
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}
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break;
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case VEC_MERGE:
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if (GET_MODE (op0) != mode
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|| GET_MODE (op1) != mode
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@ -3286,7 +3302,7 @@ simplify_subreg (enum machine_mode outermode, rtx op,
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of real and imaginary part. */
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if (GET_CODE (op) == CONCAT)
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{
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int is_realpart = byte < GET_MODE_UNIT_SIZE (innermode);
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int is_realpart = byte < (unsigned int) GET_MODE_UNIT_SIZE (innermode);
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rtx part = is_realpart ? XEXP (op, 0) : XEXP (op, 1);
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unsigned int final_offset;
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rtx res;
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@ -1,3 +1,8 @@
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2003-11-02 Roger Sayle <roger@eyesopen.com>
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PR optimization/10817
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* gcc.c-torture/compile/20031102-1.c: New test case.
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2003-11-02 Kazu Hirata <kazu@cs.umass.edu>
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* gcc.c-torture/execute/va-arg-25.c: Enable only if INT_MAX ==
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12
gcc/testsuite/gcc.c-torture/compile/20031102-1.c
Normal file
12
gcc/testsuite/gcc.c-torture/compile/20031102-1.c
Normal file
@ -0,0 +1,12 @@
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/* PR optimization/10817.
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Check that the following code doesn't cause any problems
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for GCC's if-conversion passes. */
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int foo(int t)
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{
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int result = 0;
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if (t != 0)
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result = t;
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return result;
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}
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