diff options
| -rw-r--r-- | gcc/ChangeLog | 7 | ||||
| -rw-r--r-- | gcc/doc/rtl.texi | 26 | ||||
| -rw-r--r-- | gcc/rtl.def | 6 | ||||
| -rw-r--r-- | gcc/simplify-rtx.c | 3 |
4 files changed, 38 insertions, 4 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index f41b3a9..9f19a12 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,10 @@ +2006-04-24 Bernd Schmidt <bernd.schmidt@analog.com> + + * rtl.def (SS_ASHIFT, SS_NEG): New codes. + * doc/rtl.texi: Document them. + * simplify-rtx.c (simplify_unary_operation, + simplify_binary_operation_1): Don't abort when we see them. + 2006-04-24 Mark Mitchell <mark@codesourcery.com> Revert: diff --git a/gcc/doc/rtl.texi b/gcc/doc/rtl.texi index 71e6df7..87f13d8 100644 --- a/gcc/doc/rtl.texi +++ b/gcc/doc/rtl.texi @@ -1889,9 +1889,18 @@ or the first operand must be loaded into a register while its mode is still known. @findex neg +@findex ss_neg +@cindex negation +@cindex negation with signed saturation @item (neg:@var{m} @var{x}) -Represents the negation (subtraction from zero) of the value represented -by @var{x}, carried out in mode @var{m}. +@itemx (ss_neg:@var{m} @var{x}) +These two expressions represent the negation (subtraction from zero) of +the value represented by @var{x}, carried out in mode @var{m}. They +differ in the behaviour on overflow of integer modes. In the case of +@code{neg}, the negation of the operand may be a number not representable +in mode @var{m}, in which case it is truncated to @var{m}. @code{ss_neg} +ensures that an out-of-bounds result saturates to the maximum or minimum +representable value. @findex mult @cindex multiplication @@ -1998,12 +2007,21 @@ and @var{y}, carried out in machine mode @var{m}, which must be a fixed-point mode. @findex ashift +@findex ss_ashift @cindex left shift @cindex shift @cindex arithmetic shift +@cindex arithmetic shift with signed saturation @item (ashift:@var{m} @var{x} @var{c}) -Represents the result of arithmetically shifting @var{x} left by @var{c} -places. @var{x} have mode @var{m}, a fixed-point machine mode. @var{c} +@itemx (ss_ashift:@var{m} @var{x} @var{c}) +These two expressions epresent the result of arithmetically shifting @var{x} +left by @var{c} places. They differ in their behavior on overflow of integer +modes. An @code{ashift} operation is a plain shift with no special behaviour +in case of a change in the sign bit; @code{ss_ashift} saturates to the minimum +or maximum representable value rather than allowing the shift to change the +sign bit of the value. + +@var{x} have mode @var{m}, a fixed-point machine mode. @var{c} be a fixed-point mode or be a constant with mode @code{VOIDmode}; which mode is determined by the mode called for in the machine description entry for the left-shift instruction. For example, on the VAX, the mode diff --git a/gcc/rtl.def b/gcc/rtl.def index 4c5a632..847b51c 100644 --- a/gcc/rtl.def +++ b/gcc/rtl.def @@ -642,6 +642,12 @@ DEF_RTL_EXPR(US_PLUS, "us_plus", "ee", RTX_COMM_ARITH) /* Operand 0 minus operand 1, with signed saturation. */ DEF_RTL_EXPR(SS_MINUS, "ss_minus", "ee", RTX_BIN_ARITH) +/* Negation with signed saturation. */ +DEF_RTL_EXPR(SS_NEG, "ss_neg", "e", RTX_UNARY) + +/* Shift left with signed saturation. */ +DEF_RTL_EXPR(SS_ASHIFT, "ss_ashift", "ee", RTX_BIN_ARITH) + /* Operand 0 minus operand 1, with unsigned saturation. */ DEF_RTL_EXPR(US_MINUS, "us_minus", "ee", RTX_BIN_ARITH) diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index 0ce033d..962c2de 100644 --- a/gcc/simplify-rtx.c +++ b/gcc/simplify-rtx.c @@ -1092,6 +1092,7 @@ simplify_const_unary_operation (enum rtx_code code, enum machine_mode mode, case FLOAT_TRUNCATE: case SS_TRUNCATE: case US_TRUNCATE: + case SS_NEG: return 0; default: @@ -2422,6 +2423,7 @@ simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode, /* Fall through.... */ case ASHIFT: + case SS_ASHIFT: case LSHIFTRT: if (trueop1 == CONST0_RTX (mode)) return op0; @@ -3110,6 +3112,7 @@ simplify_const_binary_operation (enum rtx_code code, enum machine_mode mode, case US_PLUS: case SS_MINUS: case US_MINUS: + case SS_ASHIFT: /* ??? There are simplifications that can be done. */ return 0; |