diff options
| author | Richard Kenner <kenner@gcc.gnu.org> | 1996-10-21 07:39:13 -0400 |
|---|---|---|
| committer | Richard Kenner <kenner@gcc.gnu.org> | 1996-10-21 07:39:13 -0400 |
| commit | 04d23d7c9f04fd64de62c839e63426760254df68 (patch) | |
| tree | 82b8fc55666e5af0125012c7a5965a2fd39e54cd /gcc | |
| parent | 1cd4bca92c2407e0884540c1d67694ac856bfcdf (diff) | |
| download | gcc-04d23d7c9f04fd64de62c839e63426760254df68.zip gcc-04d23d7c9f04fd64de62c839e63426760254df68.tar.gz gcc-04d23d7c9f04fd64de62c839e63426760254df68.tar.bz2 | |
(jump_optimize): Use emit_store_flag even if branches are cheap, if
the store is even cheaper.
From-SVN: r12982
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/jump.c | 27 |
1 files changed, 17 insertions, 10 deletions
@@ -1,5 +1,5 @@ /* Optimize jump instructions, for GNU compiler. - Copyright (C) 1987, 88, 89, 91-95, 1996 Free Software Foundation, Inc.b + Copyright (C) 1987, 88, 89, 91-95, 1996 Free Software Foundation, Inc. This file is part of GNU CC. @@ -1165,13 +1165,9 @@ jump_optimize (f, cross_jump, noop_moves, after_regscan) We could handle BLKmode if (1) emit_store_flag could and (2) we could find the size reliably. */ && GET_MODE (XEXP (temp4, 0)) != BLKmode - /* No point in doing any of this if branches are cheap or we - don't have conditional moves. */ - && (BRANCH_COST >= 2 -#ifdef HAVE_conditional_move - || 1 -#endif - ) + /* Even if branches are cheap, the store_flag optimization + can win when the operation to be performed can be + expressed directly. */ #ifdef HAVE_cc0 /* If the previous insn sets CC0 and something else, we can't do this since we are going to delete that insn. */ @@ -1282,8 +1278,19 @@ jump_optimize (f, cross_jump, noop_moves, after_regscan) can reverse the condition. See if (3) applies possibly by reversing the condition. Prefer reversing to (4) when branches are very expensive. */ - && ((reversep = 0, temp2 == const0_rtx) - || (temp3 == const0_rtx + && (((BRANCH_COST >= 2 + || STORE_FLAG_VALUE == -1 + || (STORE_FLAG_VALUE == 1 + /* Check that the mask is a power of two, + so that it can probably be generated + with a shift. */ + && exact_log2 (INTVAL (temp3)) >= 0)) + && (reversep = 0, temp2 == const0_rtx)) + || ((BRANCH_COST >= 2 + || STORE_FLAG_VALUE == -1 + || (STORE_FLAG_VALUE == 1 + && exact_log2 (INTVAL (temp2)) >= 0)) + && temp3 == const0_rtx && (reversep = can_reverse_comparison_p (temp4, insn))) || (BRANCH_COST >= 2 && GET_CODE (temp2) == CONST_INT |