Hello,
this patch adds support for generating usat/ssat instructions to match code
along the lines of:
if (a < amin) return amin;
else if (a > amax) return amax;
else return a;
for appropriate values of amin/amax. This type code actually occurs in
real-life code (e.g. codecs).
Above code is already translated into a sequence of SMIN/SMAX RTX
operations by expand. The combine pass is able to fold those into
a single RTX pattern, so we only need to make such patterns available
to match the instruction. Note that usat/ssat may in addition shift
their input operand; this is also supported by the patch.
There are already pre-existing patterns that use usat/ssat to
implement us_truncate/ss_truncate. Those represent special
cases of the general instructions, and are left in place by
this patch. (However, some minor fixes e.g. to the sat_shift_operator
predicate and insn attributes apply to those patterns too.)
Tested on arm-linux-gnueabi with no regressions.
OK for 4.8?
Bye,
Ulrich
ChangeLog:
gcc/
* config/arm/arm.c (arm_sat_operator_match): New function.
* config/arm/arm-protos.h (arm_sat_operator_match): Add prototype.
* config/arm/arm.md ("insn" attribute): Add "sat" value.
("SAT", "SATrev"): New code iterators.
("SATlo", "SAThi"): New code iterator attributes.
("*satsi_<SAT:code>"): New pattern.
("*satsi_<SAT:code>_shift"): Likewise.
* config/arm/arm-fixed.md ("arm_ssatsihi_shift"): Add "insn"
and "shift" attributes.
("arm_usatsihi"): Add "insn" attribute.
* config/arm/predicates.md (sat_shift_operator): Allow multiplication
by powers of two. Do not allow shift by 32.
gcc/testsuite/
* gcc.target/arm/sat-1.c: New test.
Index: gcc/testsuite/gcc.target/arm/sat-1.c
===================================================================
--- gcc/testsuite/gcc.target/arm/sat-1.c (revision 0)
+++ gcc/testsuite/gcc.target/arm/sat-1.c (revision 0)
@@ -0,0 +1,64 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target arm_arm_ok } */
+/* { dg-require-effective-target arm_arch_v6_ok } */
+/* { dg-options "-O2 -marm" } */
+/* { dg-add-options arm_arch_v6 } */
+
+
+static inline int sat1 (int a, int amin, int amax)
+{
+ if (a < amin) return amin;
+ else if (a > amax) return amax;
+ else return a;
+}
+
+static inline int sat2 (int a, int amin, int amax)
+{
+ if (a > amax) return amax;
+ else if (a < amin) return amin;
+ else return a;
+}
+
+int u1 (int x)
+{
+ return sat1 (x, 0, 63);
+}
+
+int us1 (int x)
+{
+ return sat1 (x >> 5, 0, 63);
+}
+
+int s1 (int x)
+{
+ return sat1 (x, -64, 63);
+}
+
+int ss1 (int x)
+{
+ return sat1 (x >> 5, -64, 63);
+}
+
+int u2 (int x)
+{
+ return sat2 (x, 0, 63);
+}
+
+int us2 (int x)
+{
+ return sat2 (x >> 5, 0, 63);
+}
+
+int s2 (int x)
+{
+ return sat2 (x, -64, 63);
+}
+
+int ss2 (int x)
+{
+ return sat2 (x >> 5, -64, 63);
+}
+
+/* { dg-final { scan-assembler-times "usat" 4 } } */
+/* { dg-final { scan-assembler-times "ssat" 4 } } */
+
Index: gcc/config/arm/arm.c
===================================================================
--- gcc/config/arm/arm.c (revision 184553)
+++ gcc/config/arm/arm.c (working copy)
@@ -10041,6 +10041,42 @@
}
}
+/* Match pair of min/max operators that can be implemented via usat/ssat. */
+
+bool
+arm_sat_operator_match (rtx lo_bound, rtx hi_bound,
+ int *mask, bool *signed_sat)
+{
+ /* The high bound must be a power of two minus one. */
+ int log = exact_log2 (INTVAL (hi_bound) + 1);
+ if (log == -1)
+ return false;
+
+ /* The low bound is either zero (for usat) or one less than the
+ negation of the high bound (for ssat). */
+ if (INTVAL (lo_bound) == 0)
+ {
+ if (mask)
+ *mask = log;
+ if (signed_sat)
+ *signed_sat = false;
+
+ return true;
+ }
+
+ if (INTVAL (lo_bound) == -INTVAL (hi_bound) - 1)
+ {
+ if (mask)
+ *mask = log + 1;
+ if (signed_sat)
+ *signed_sat = true;
+
+ return true;
+ }
+
+ return false;
+}
+
/* Return 1 if memory locations are adjacent. */
int
adjacent_mem_locations (rtx a, rtx b)
Index: gcc/config/arm/arm-fixed.md
===================================================================
--- gcc/config/arm/arm-fixed.md (revision 184553)
+++ gcc/config/arm/arm-fixed.md (working copy)
@@ -374,6 +374,8 @@
"TARGET_32BIT && arm_arch6"
"ssat%?\\t%0, #16, %2%S1"
[(set_attr "predicable" "yes")
+ (set_attr "insn" "sat")
+ (set_attr "shift" "1")
(set_attr "type" "alu_shift")])
(define_insn "arm_usatsihi"
@@ -381,4 +383,5 @@
(us_truncate:HI (match_operand:SI 1 "s_register_operand")))]
"TARGET_INT_SIMD"
"usat%?\\t%0, #16, %1"
- [(set_attr "predicable" "yes")])
+ [(set_attr "predicable" "yes")
+ (set_attr "insn" "sat")])
Index: gcc/config/arm/arm-protos.h
===================================================================
--- gcc/config/arm/arm-protos.h (revision 184553)
+++ gcc/config/arm/arm-protos.h (working copy)
@@ -107,6 +107,7 @@
extern int symbol_mentioned_p (rtx);
extern int label_mentioned_p (rtx);
extern RTX_CODE minmax_code (rtx);
+extern bool arm_sat_operator_match (rtx, rtx, int *, bool *);
extern int adjacent_mem_locations (rtx, rtx);
extern bool gen_ldm_seq (rtx *, int, bool);
extern bool gen_stm_seq (rtx *, int);
Index: gcc/config/arm/predicates.md
===================================================================
--- gcc/config/arm/predicates.md (revision 184553)
+++ gcc/config/arm/predicates.md (working copy)
@@ -243,9 +243,11 @@
;; True for shift operators which can be used with saturation instructions.
(define_special_predicate "sat_shift_operator"
- (and (match_code "ashift,ashiftrt")
- (match_test "GET_CODE (XEXP (op, 1)) == CONST_INT
- && ((unsigned HOST_WIDE_INT) INTVAL (XEXP (op, 1)) <= 32)")
+ (and (ior (and (match_code "mult")
+ (match_test "power_of_two_operand (XEXP (op, 1), mode)"))
+ (and (match_code "ashift,ashiftrt")
+ (match_test "GET_CODE (XEXP (op, 1)) == CONST_INT
+ && ((unsigned HOST_WIDE_INT) INTVAL (XEXP (op,
1)) < 32)")))
(match_test "mode == GET_MODE (op)")))
;; True for MULT, to identify which variant of shift_operator is in use.
Index: gcc/config/arm/arm.md
===================================================================
--- gcc/config/arm/arm.md (revision 184553)
+++ gcc/config/arm/arm.md (working copy)
@@ -283,7 +283,7 @@
;; scheduling information.
(define_attr "insn"
-
"mov,mvn,smulxy,smlaxy,smlalxy,smulwy,smlawx,mul,muls,mla,mlas,umull,umulls,umlal,umlals,smull,smulls,smlal,smlals,smlawy,smuad,smuadx,smlad,smladx,smusd,smusdx,smlsd,smlsdx,smmul,smmulr,smmla,umaal,smlald,smlsld,clz,mrs,msr,xtab,sdiv,udiv,other"
+
"mov,mvn,smulxy,smlaxy,smlalxy,smulwy,smlawx,mul,muls,mla,mlas,umull,umulls,umlal,umlals,smull,smulls,smlal,smlals,smlawy,smuad,smuadx,smlad,smladx,smusd,smusdx,smlsd,smlsdx,smmul,smmulr,smmla,umaal,smlald,smlsld,clz,mrs,msr,xtab,sdiv,udiv,sat,other"
(const_string "other"))
; TYPE attribute is used to detect floating point instructions which, if
@@ -3446,6 +3446,60 @@
(const_int 12)))]
)
+(define_code_iterator SAT [smin smax])
+(define_code_iterator SATrev [smin smax])
+(define_code_attr SATlo [(smin "1") (smax "2")])
+(define_code_attr SAThi [(smin "2") (smax "1")])
+
+(define_insn "*satsi_<SAT:code>"
+ [(set (match_operand:SI 0 "s_register_operand" "=r")
+ (SAT:SI (SATrev:SI (match_operand:SI 3 "s_register_operand" "r")
+ (match_operand:SI 1 "const_int_operand" "i"))
+ (match_operand:SI 2 "const_int_operand" "i")))]
+ "TARGET_32BIT && arm_arch6 && <SAT:CODE> != <SATrev:CODE>
+ && arm_sat_operator_match (operands[<SAT:SATlo>], operands[<SAT:SAThi>],
NULL, NULL)"
+{
+ int mask;
+ bool signed_sat;
+ if (!arm_sat_operator_match (operands[<SAT:SATlo>], operands[<SAT:SAThi>],
+ &mask, &signed_sat))
+ gcc_unreachable ();
+
+ operands[1] = GEN_INT (mask);
+ if (signed_sat)
+ return "ssat%?\t%0, %1, %3";
+ else
+ return "usat%?\t%0, %1, %3";
+}
+ [(set_attr "predicable" "yes")
+ (set_attr "insn" "sat")])
+
+(define_insn "*satsi_<SAT:code>_shift"
+ [(set (match_operand:SI 0 "s_register_operand" "=r")
+ (SAT:SI (SATrev:SI (match_operator:SI 3 "sat_shift_operator"
+ [(match_operand:SI 4 "s_register_operand" "r")
+ (match_operand:SI 5 "const_int_operand" "i")])
+ (match_operand:SI 1 "const_int_operand" "i"))
+ (match_operand:SI 2 "const_int_operand" "i")))]
+ "TARGET_32BIT && arm_arch6 && <SAT:CODE> != <SATrev:CODE>
+ && arm_sat_operator_match (operands[<SAT:SATlo>], operands[<SAT:SAThi>],
NULL, NULL)"
+{
+ int mask;
+ bool signed_sat;
+ if (!arm_sat_operator_match (operands[<SAT:SATlo>], operands[<SAT:SAThi>],
+ &mask, &signed_sat))
+ gcc_unreachable ();
+
+ operands[1] = GEN_INT (mask);
+ if (signed_sat)
+ return "ssat%?\t%0, %1, %4%S3";
+ else
+ return "usat%?\t%0, %1, %4%S3";
+}
+ [(set_attr "predicable" "yes")
+ (set_attr "insn" "sat")
+ (set_attr "shift" "3")
+ (set_attr "type" "alu_shift")])
;; Shift and rotation insns
--
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE
ulrich.weig...@de.ibm.com
