This patch improves the code generated for DImode right shifts (both
arithmetic and logical) by a single bit, and also for DImode rotates
(both left and right) by a single bit. In approach, this is similar
to the recently added DImode left shift by a single bit patch, but
also builds upon i386.md's UNSPEC carry flag representation:
https://gcc.gnu.org/pipermail/gcc-patches/2023-October/632169.html
The benefits can be seen from the four new test cases:
long long ashr(long long x) { return x >> 1; }
Before:
ashr: asl r2,r1,31
lsr_s r0,r0
or_s r0,r0,r2
j_s.d [blink]
asr_s r1,r1,1
After:
ashr: asr.f r1,r1
j_s.d [blink]
rrc r0,r0
unsigned long long lshr(unsigned long long x) { return x >> 1; }
Before:
lshr: asl r2,r1,31
lsr_s r0,r0
or_s r0,r0,r2
j_s.d [blink]
lsr_s r1,r1
After:
lshr: lsr.f r1,r1
j_s.d [blink]
rrc r0,r0
unsigned long long rotl(unsigned long long x) { return (x<<1) | (x>>63); }
Before:
rotl: lsr r12,r1,31
lsr r2,r0,31
asl_s r3,r0,1
asl_s r1,r1,1
or r0,r12,r3
j_s.d [blink]
or_s r1,r1,r2
After:
rotl: add.f r0,r0,r0
adc.f r1,r1,r1
j_s.d [blink]
add.cs r0,r0,1
unsigned long long rotr(unsigned long long x) { return (x>>1) | (x<<63); }
Before:
rotr: asl r12,r1,31
asl r2,r0,31
lsr_s r3,r0
lsr_s r1,r1
or r0,r12,r3
j_s.d [blink]
or_s r1,r1,r2
After:
rotr: asr.f 0,r0
rrc.f r1,r1
j_s.d [blink]
rrc r0,r0
On CPUs without a barrel shifter the improvements are even better.
Tested with a cross-compiler to arc-linux hosted on x86_64,
with no new (compile-only) regressions from make -k check.
Ok for mainline if this passes Claudiu's nightly testing?
2023-11-06 Roger Sayle <ro...@nextmovesoftware.com>
gcc/ChangeLog
* config/arc/arc.md (UNSPEC_ARC_CC_NEZ): New UNSPEC that
represents the carry flag being set if the operand is non-zero.
(adc_f): New define_insn representing adc with updated flags.
(ashrdi3): New define_expand that only handles shifts by 1.
(ashrdi3_cnt1): New pre-reload define_insn_and_split.
(lshrdi3): New define_expand that only handles shifts by 1.
(lshrdi3_cnt1): New pre-reload define_insn_and_split.
(rrcsi2): New define_insn for rrc (SImode rotate right through
carry).
(rrcsi2_carry): Likewise for rrc.f, as above but updating flags.
(rotldi3): New define_expand that only handles rotates by 1.
(rotldi3_cnt1): New pre-reload define_insn_and_split.
(rotrdi3): New define_expand that only handles rotates by 1.
(rotrdi3_cnt1): New pre-reload define_insn_and_split.
(lshrsi3_cnt1_carry): New define_insn for lsr.f.
(ashrsi3_cnt1_carry): New define_insn for asr.f.
(btst_0_carry): New define_insn for asr.f without result.
gcc/testsuite/ChangeLog
* gcc.target/arc/ashrdi3-1.c: New test case.
* gcc.target/arc/lshrdi3-1.c: Likewise.
* gcc.target/arc/rotldi3-1.c: Likewise.
* gcc.target/arc/rotrdi3-1.c: Likewise.
Thanks in advance,
Roger
--
diff --git a/gcc/config/arc/arc.md b/gcc/config/arc/arc.md
index 7702978..97231b9 100644
--- a/gcc/config/arc/arc.md
+++ b/gcc/config/arc/arc.md
@@ -137,6 +137,7 @@
UNSPEC_ARC_VMAC2HU
UNSPEC_ARC_VMPY2H
UNSPEC_ARC_VMPY2HU
+ UNSPEC_ARC_CC_NEZ
VUNSPEC_ARC_RTIE
VUNSPEC_ARC_SYNC
@@ -2790,6 +2791,31 @@ archs4x, archs4xd"
(set_attr "type" "cc_arith")
(set_attr "length" "4,4,4,4,8,8")])
+(define_insn "adc_f"
+ [(set (reg:CC_C CC_REG)
+ (compare:CC_C
+ (zero_extend:DI
+ (plus:SI
+ (plus:SI
+ (ltu:SI (reg:CC_C CC_REG) (const_int 0))
+ (match_operand:SI 1 "register_operand" "%r"))
+ (match_operand:SI 2 "register_operand" "r")))
+ (plus:DI
+ (ltu:DI (reg:CC_C CC_REG) (const_int 0))
+ (zero_extend:DI (match_dup 1)))))
+ (set (match_operand:SI 0 "register_operand" "=r")
+ (plus:SI
+ (plus:SI
+ (ltu:SI (reg:CC_C CC_REG) (const_int 0))
+ (match_dup 1))
+ (match_dup 2)))]
+ ""
+ "adc.f\\t%0,%1,%2"
+ [(set_attr "cond" "set")
+ (set_attr "predicable" "no")
+ (set_attr "type" "cc_arith")
+ (set_attr "length" "4")])
+
; combiner-splitter cmp / scc -> cmp / adc
(define_split
[(set (match_operand:SI 0 "dest_reg_operand" "")
@@ -3530,6 +3556,68 @@ archs4x, archs4xd"
""
[(set_attr "length" "8")])
+(define_expand "ashrdi3"
+ [(parallel
+ [(set (match_operand:DI 0 "register_operand")
+ (ashiftrt:DI (match_operand:DI 1 "register_operand")
+ (match_operand:QI 2 "const_int_operand")))
+ (clobber (reg:CC CC_REG))])]
+ ""
+{
+ if (operands[2] != const1_rtx)
+ FAIL;
+})
+
+;; Split into asr.f hi; rrc lo
+(define_insn_and_split "*ashrdi3_cnt1"
+ [(set (match_operand:DI 0 "register_operand")
+ (ashiftrt:DI (match_operand:DI 1 "register_operand")
+ (const_int 1)))
+ (clobber (reg:CC CC_REG))]
+ "arc_pre_reload_split ()"
+ "#"
+ "&& 1"
+ [(const_int 0)]
+{
+ emit_insn (gen_ashrsi3_cnt1_carry (gen_highpart (SImode, operands[0]),
+ gen_highpart (SImode, operands[1])));
+ emit_insn (gen_rrcsi2 (gen_lowpart (SImode, operands[0]),
+ gen_lowpart (SImode, operands[1])));
+ DONE;
+}
+ [(set_attr "length" "8")])
+
+(define_expand "lshrdi3"
+ [(parallel
+ [(set (match_operand:DI 0 "register_operand")
+ (lshiftrt:DI (match_operand:DI 1 "register_operand")
+ (match_operand:QI 2 "const_int_operand")))
+ (clobber (reg:CC CC_REG))])]
+ ""
+{
+ if (operands[2] != const1_rtx)
+ FAIL;
+})
+
+;; Split into lsr.f hi; rrc lo
+(define_insn_and_split "*lshrdi3_cnt1"
+ [(set (match_operand:DI 0 "register_operand")
+ (lshiftrt:DI (match_operand:DI 1 "register_operand")
+ (const_int 1)))
+ (clobber (reg:CC CC_REG))]
+ "arc_pre_reload_split ()"
+ "#"
+ "&& 1"
+ [(const_int 0)]
+{
+ emit_insn (gen_lshrsi3_cnt1_carry (gen_highpart (SImode, operands[0]),
+ gen_highpart (SImode, operands[1])));
+ emit_insn (gen_rrcsi2 (gen_lowpart (SImode, operands[0]),
+ gen_lowpart (SImode, operands[1])));
+ DONE;
+}
+ [(set_attr "length" "8")])
+
;; Rotate instructions.
(define_insn "rotrsi3_insn"
@@ -3571,6 +3659,103 @@ archs4x, archs4xd"
}
})
+;; Rotate through carry flag
+
+(define_insn "rrcsi2"
+ [(set (match_operand:SI 0 "dest_reg_operand" "=r")
+ (plus:SI
+ (lshiftrt:SI (match_operand:SI 1 "register_operand" "r")
+ (const_int 1))
+ (ashift:SI (ltu:SI (reg:CC_C CC_REG) (const_int 0))
+ (const_int 31))))]
+ ""
+ "rrc\\t%0,%1"
+ [(set_attr "type" "shift")
+ (set_attr "predicable" "no")
+ (set_attr "length" "4")])
+
+(define_insn "rrcsi2_carry"
+ [(set (reg:CC_C CC_REG)
+ (unspec:CC_C [(and:SI (match_operand:SI 1 "register_operand" "r")
+ (const_int 1))] UNSPEC_ARC_CC_NEZ))
+ (set (match_operand:SI 0 "dest_reg_operand" "=r")
+ (plus:SI
+ (lshiftrt:SI (match_dup 1) (const_int 1))
+ (ashift:SI (ltu:SI (reg:CC_C CC_REG) (const_int 0))
+ (const_int 31))))]
+ ""
+ "rrc.f\\t%0,%1"
+ [(set_attr "type" "shift")
+ (set_attr "predicable" "no")
+ (set_attr "length" "4")])
+
+;; DImode Rotate instructions
+
+(define_expand "rotldi3"
+ [(parallel
+ [(set (match_operand:DI 0 "register_operand")
+ (rotate:DI (match_operand:DI 1 "register_operand")
+ (match_operand:QI 2 "const_int_operand")))
+ (clobber (reg:CC CC_REG))])]
+ ""
+{
+ if (operands[2] != const1_rtx)
+ FAIL;
+})
+
+;; split into add.f lo; adc.f hi; adc lo
+(define_insn_and_split "*rotldi3_cnt1"
+ [(set (match_operand:DI 0 "register_operand")
+ (rotate:DI (match_operand:DI 1 "register_operand")
+ (const_int 1)))
+ (clobber (reg:CC CC_REG))]
+ "arc_pre_reload_split ()"
+ "#"
+ "&& 1"
+ [(const_int 0)]
+{
+ rtx lo0 = gen_lowpart (SImode, operands[0]);
+ rtx lo1 = gen_lowpart (SImode, operands[1]);
+ rtx hi1 = gen_highpart (SImode, operands[1]);
+ emit_insn (gen_add_f (lo0, lo1, lo1));
+ emit_insn (gen_adc_f (gen_highpart (SImode, operands[0]), hi1, hi1));
+ emit_insn (gen_adc (lo0, lo0, const0_rtx));
+ DONE;
+}
+ [(set_attr "length" "12")])
+
+(define_expand "rotrdi3"
+ [(parallel
+ [(set (match_operand:DI 0 "register_operand")
+ (rotatert:DI (match_operand:DI 1 "register_operand")
+ (match_operand:QI 2 "const_int_operand")))
+ (clobber (reg:CC CC_REG))])]
+ ""
+{
+ if (operands[2] != const1_rtx)
+ FAIL;
+})
+
+;; split into asr.f lo; rrc.f hi; rrc lo
+(define_insn_and_split "*rotrdi3_cnt1"
+ [(set (match_operand:DI 0 "register_operand")
+ (rotatert:DI (match_operand:DI 1 "register_operand")
+ (const_int 1)))
+ (clobber (reg:CC CC_REG))]
+ "arc_pre_reload_split ()"
+ "#"
+ "&& 1"
+ [(const_int 0)]
+{
+ rtx lo = gen_lowpart (SImode, operands[1]);
+ emit_insn (gen_btst_0_carry (lo));
+ emit_insn (gen_rrcsi2_carry (gen_highpart (SImode, operands[0]),
+ gen_highpart (SImode, operands[1])));
+ emit_insn (gen_rrcsi2 (gen_lowpart (SImode, operands[0]), lo));
+ DONE;
+}
+ [(set_attr "length" "12")])
+
;; Compare / branch instructions.
(define_expand "cbranchsi4"
@@ -6022,6 +6207,18 @@ archs4x, archs4xd"
(set_attr "iscompact" "maybe,false")
(set_attr "predicable" "no,no")])
+(define_insn "lshrsi3_cnt1_carry"
+ [(set (reg:CC_C CC_REG)
+ (unspec:CC_C [(and:SI (match_operand:SI 1 "register_operand" "r")
+ (const_int 1))] UNSPEC_ARC_CC_NEZ))
+ (set (match_operand:SI 0 "dest_reg_operand" "=r")
+ (lshiftrt:SI (match_dup 1) (const_int 1)))]
+ ""
+ "lsr.f\\t%0,%1"
+ [(set_attr "type" "unary")
+ (set_attr "length" "4")
+ (set_attr "predicable" "no")])
+
(define_insn "ashrsi3_cnt1"
[(set (match_operand:SI 0 "dest_reg_operand" "=q,w")
(ashiftrt:SI (match_operand:SI 1 "register_operand" "q,c")
@@ -6032,6 +6229,28 @@ archs4x, archs4xd"
(set_attr "iscompact" "maybe,false")
(set_attr "predicable" "no,no")])
+(define_insn "ashrsi3_cnt1_carry"
+ [(set (reg:CC_C CC_REG)
+ (unspec:CC_C [(and:SI (match_operand:SI 1 "register_operand" "r")
+ (const_int 1))] UNSPEC_ARC_CC_NEZ))
+ (set (match_operand:SI 0 "dest_reg_operand" "=r")
+ (ashiftrt:SI (match_dup 1) (const_int 1)))]
+ ""
+ "asr.f\\t%0,%1"
+ [(set_attr "type" "unary")
+ (set_attr "length" "4")
+ (set_attr "predicable" "no")])
+
+(define_insn "btst_0_carry"
+ [(set (reg:CC_C CC_REG)
+ (unspec:CC_C [(and:SI (match_operand:SI 0 "register_operand" "r")
+ (const_int 1))] UNSPEC_ARC_CC_NEZ))]
+ ""
+ "asr.f\\t0,%0"
+ [(set_attr "type" "unary")
+ (set_attr "length" "4")
+ (set_attr "predicable" "no")])
+
(define_peephole2
[(set (match_operand:SI 0 "register_operand" "")
(zero_extract:SI (match_dup 0)
diff --git a/gcc/testsuite/gcc.target/arc/ashrdi3-1.c
b/gcc/testsuite/gcc.target/arc/ashrdi3-1.c
new file mode 100644
index 0000000..d990bfd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arc/ashrdi3-1.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+long long foo(long long x)
+{
+ return x >> 1;
+}
+
+/* { dg-final { scan-assembler "asr.f\\s+r1,r1" } } */
+/* { dg-final { scan-assembler "rrc\\s+r0,r0" } } */
diff --git a/gcc/testsuite/gcc.target/arc/lshrdi3-1.c
b/gcc/testsuite/gcc.target/arc/lshrdi3-1.c
new file mode 100644
index 0000000..6542ffd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arc/lshrdi3-1.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned long long foo(unsigned long long x)
+{
+ return x >> 1;
+}
+
+/* { dg-final { scan-assembler "lsr.f\\s+r1,r1" } } */
+/* { dg-final { scan-assembler "rrc\\s+r0,r0" } } */
diff --git a/gcc/testsuite/gcc.target/arc/rotldi3-1.c
b/gcc/testsuite/gcc.target/arc/rotldi3-1.c
new file mode 100644
index 0000000..325996e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arc/rotldi3-1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned long long foo(unsigned long long x)
+{
+ return (x << 1) | (x >> 63);
+}
+
+/* { dg-final { scan-assembler "add.f\\s+r0,r0,r0" } } */
+/* { dg-final { scan-assembler "adc.f\\s+r1,r1,r1" } } */
+/* { dg-final { scan-assembler "add.cs\\s+r0,r0,1" } } */
diff --git a/gcc/testsuite/gcc.target/arc/rotrdi3-1.c
b/gcc/testsuite/gcc.target/arc/rotrdi3-1.c
new file mode 100644
index 0000000..cd8e0de
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arc/rotrdi3-1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned long long foo(unsigned long long x)
+{
+ return (x >> 1) | (x << 63);
+}
+
+/* { dg-final { scan-assembler "asr.f\\s+0,r0" } } */
+/* { dg-final { scan-assembler "rrc.f\\s+r1,r1" } } */
+/* { dg-final { scan-assembler "rrc\\s+r0,r0" } } */
