RISC-V: Add zero_extract support for rv64gc

The combiner attempts to optimize a zero-extension of a logical right shift
using zero_extract. We already utilize this optimization for those cases
that result in a single instructions.  Let's add a insn_and_split
pattern that also matches the generic case, where we can emit an
optimized sequence of a slli/srli.

Tested with SPEC CPU 2017 (rv64gc).

	PR target/111501

gcc/ChangeLog:

	* config/riscv/riscv.md (*lshr<GPR:mode>3_zero_extend_4): New
	pattern for zero-extraction.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/extend-shift-helpers.h: New test.
	* gcc.target/riscv/pr111501.c: New test.
	* gcc.target/riscv/zero-extend-rshift-32.c: New test.
	* gcc.target/riscv/zero-extend-rshift-64.c: New test.
	* gcc.target/riscv/zero-extend-rshift.c: New test.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>

6 files changed, 222 insertions, 0 deletions

diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index b7fc13e..58bf771 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -2793,6 +2793,36 @@
   [(set_attr "type" "shift")
    (set_attr "mode" "SI")])
 
+;; Canonical form for a zero-extend of a logical right shift.
+;; Special cases are handled above.
+;; Skip for single-bit extraction (Zbs/XTheadBs) and th.extu (XTheadBb)
+(define_insn_and_split "*lshr<GPR:mode>3_zero_extend_4"
+  [(set (match_operand:GPR 0 "register_operand" "=r")
+	 (zero_extract:GPR
+       (match_operand:GPR 1 "register_operand" " r")
+       (match_operand     2 "const_int_operand")
+       (match_operand     3 "const_int_operand")))
+   (clobber (match_scratch:GPR  4 "=&r"))]
+  "!((TARGET_ZBS || TARGET_XTHEADBS) && (INTVAL (operands[2]) == 1))
+   && !TARGET_XTHEADBB"
+  "#"
+  "&& reload_completed"
+  [(set (match_dup 4)
+     (ashift:GPR (match_dup 1) (match_dup 2)))
+   (set (match_dup 0)
+     (lshiftrt:GPR (match_dup 4) (match_dup 3)))]
+{
+  int regbits = GET_MODE_BITSIZE (GET_MODE (operands[0])).to_constant ();
+  int sizebits = INTVAL (operands[2]);
+  int startbits = INTVAL (operands[3]);
+  int lshamt = regbits - sizebits - startbits;
+  int rshamt = lshamt + startbits;
+  operands[2] = GEN_INT (lshamt);
+  operands[3] = GEN_INT (rshamt);
+}
+  [(set_attr "type" "shift")
+   (set_attr "mode" "<GPR:MODE>")])
+
 ;; Handle AND with 2^N-1 for N from 12 to XLEN.  This can be split into
 ;; two logical shifts.  Otherwise it requires 3 instructions: lui,
 ;; xor/addi/srli, and.
diff --git a/gcc/testsuite/gcc.target/riscv/extend-shift-helpers.h b/gcc/testsuite/gcc.target/riscv/extend-shift-helpers.h
new file mode 100644
index 0000000..4853fe4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/extend-shift-helpers.h
@@ -0,0 +1,26 @@
+#ifndef EXTEND_SHIFT_HELPERS_H
+#define EXTEND_SHIFT_HELPERS_H
+
+#define RT_EXT_CT_RSHIFT_N_AT(RTS,RT,CTS,CT,N,ATS,AT)			\
+RTS RT									\
+RTS##_##RT##_ext_##CTS##_##CT##_rshift_##N##_##ATS##_##AT(ATS AT v)	\
+{									\
+    return (CTS CT)(v >> N);						\
+}
+
+#define ULONG_EXT_USHORT_RSHIFT_N_ULONG(N) \
+	RT_EXT_CT_RSHIFT_N_AT(unsigned,long,unsigned,short,N,unsigned,long)
+
+#define ULONG_EXT_UINT_RSHIFT_N_ULONG(N) \
+	RT_EXT_CT_RSHIFT_N_AT(unsigned,long,unsigned,int,N,unsigned,long)
+
+#define UINT_EXT_USHORT_RSHIFT_N_UINT(N) \
+	RT_EXT_CT_RSHIFT_N_AT(unsigned,int,unsigned,short,N,unsigned,int)
+
+#define UINT_EXT_USHORT_RSHIFT_N_ULONG(N) \
+	RT_EXT_CT_RSHIFT_N_AT(unsigned,int,unsigned,short,N,unsigned,long)
+
+#define ULONG_EXT_USHORT_RSHIFT_N_UINT(N) \
+	RT_EXT_CT_RSHIFT_N_AT(unsigned,long,unsigned,short,N,unsigned,int)
+
+#endif /* EXTEND_SHIFT_HELPERS_H */
diff --git a/gcc/testsuite/gcc.target/riscv/pr111501.c b/gcc/testsuite/gcc.target/riscv/pr111501.c
new file mode 100644
index 0000000..db48c34
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr111501.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target rv64 } */
+/* { dg-options "-march=rv64gc" { target { rv64 } } } */
+/* { dg-skip-if "" { *-*-* } {"-O0" "-Os" "-Og" "-Oz" "-flto" } } */
+
+unsigned int
+do_shift(unsigned long csum)
+{
+  return (unsigned short)(csum >> 32);
+}
+
+unsigned int
+do_shift2(unsigned long csum)
+{
+  return (csum << 16) >> 48;
+}
+
+/* { dg-final { scan-assembler-times "slli\t" 2 } } */
+/* { dg-final { scan-assembler-times "srli\t" 2 } } */
+/* { dg-final { scan-assembler-times "slli\ta\[0-9\],a\[0-9\],16" 2 } } */
+/* { dg-final { scan-assembler-times "srli\ta\[0-9\],a\[0-9\],48" 2 } } */
diff --git a/gcc/testsuite/gcc.target/riscv/zero-extend-rshift-32.c b/gcc/testsuite/gcc.target/riscv/zero-extend-rshift-32.c
new file mode 100644
index 0000000..c995a6e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zero-extend-rshift-32.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target rv32 } */
+/* { dg-options "-march=rv32gc" } */
+/* { dg-skip-if "" { *-*-* } {"-O0" "-Os" "-Og" "-Oz" "-flto" } } */
+
+#include "extend-shift-helpers.h"
+
+/* { dg-final { scan-assembler "slli\ta\[0-9\],a\[0-9\],2" } } */
+/* { dg-final { scan-assembler "srli\ta\[0-9\],a\[0-9\],16" } } */
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(14)
+
+/* { dg-final { scan-assembler "srli\ta\[0-9\],a\[0-9\],23" } } */
+ULONG_EXT_UINT_RSHIFT_N_ULONG(23)
diff --git a/gcc/testsuite/gcc.target/riscv/zero-extend-rshift-64.c b/gcc/testsuite/gcc.target/riscv/zero-extend-rshift-64.c
new file mode 100644
index 0000000..847fadf
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zero-extend-rshift-64.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target rv64 } */
+/* { dg-options "-march=rv64gc" } */
+/* { dg-skip-if "" { *-*-* } {"-O0" "-Os" "-Og" "-Oz" "-flto" } } */
+
+#include "extend-shift-helpers.h"
+
+/* { dg-final { scan-assembler "slli\ta\[0-9\],a\[0-9\],34" } } */
+/* { dg-final { scan-assembler "srli\ta\[0-9\],a\[0-9\],48" } } */
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(14)
+
+/* { dg-final { scan-assembler "srli\ta\[0-9\],a\[0-9\],51" } } */
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(51)
+
+/* { dg-final { scan-assembler "slli\ta\[0-9\],a\[0-9\],9" } } */
+/* { dg-final { scan-assembler "srli\ta\[0-9\],a\[0-9\],32" } } */
+ULONG_EXT_UINT_RSHIFT_N_ULONG(23)
diff --git a/gcc/testsuite/gcc.target/riscv/zero-extend-rshift.c b/gcc/testsuite/gcc.target/riscv/zero-extend-rshift.c
new file mode 100644
index 0000000..8b27b0e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zero-extend-rshift.c
@@ -0,0 +1,115 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv32gc" { target { rv32 } } } */
+/* { dg-options "-march=rv64gc" { target { rv64 } } } */
+/* { dg-skip-if "" { *-*-* } {"-O0" "-Os" "-Og" "-Oz" "-flto" } } */
+
+// Tests for merging rshifts into zero-extensions.
+// u8-casts are skipped as they can be done with one instruction (andi 0xff).
+
+#include "extend-shift-helpers.h"
+
+// Below "slli (16-N); srli 16" for rv32
+// Below "slli ((32+16)-N); srli (32+16)" for rv64
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(1)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(7)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(8)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(9)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(15)
+// Below "srli 16" for rv32
+// Below "srliw 16" for rv64
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(16)
+// Below "srli N" for rv32
+// Below "slli ((32+16)-N); srli (32+16)" for rv64
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(17)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(23)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(24)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(25)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(31)
+// Below compiler warning for rv32
+#if __riscv_xlen == 64
+// Below "slli ((32+16)-N); srli (32+16)" for rv64
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(32)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(33)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(39)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(40)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(41)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(47)
+// Below "srli N" for rv64
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(48)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(49)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(55)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(56)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(57)
+ULONG_EXT_USHORT_RSHIFT_N_ULONG(63)
+#endif /* __riscv_xlen == 64 */
+
+
+
+// Below "srli N" for rv32
+// Below "slli (32-N); srli 32" for rv64
+ULONG_EXT_UINT_RSHIFT_N_ULONG(1)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(7)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(8)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(9)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(15)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(16)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(17)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(23)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(24)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(25)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(31)
+// Below compiler warning for rv32
+#if __riscv_xlen == 64
+// Below "srli N" for rv64
+ULONG_EXT_UINT_RSHIFT_N_ULONG(32)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(33)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(39)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(40)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(41)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(47)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(48)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(49)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(55)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(56)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(57)
+ULONG_EXT_UINT_RSHIFT_N_ULONG(63)
+#endif /* __riscv_xlen == 64 */
+
+
+
+#if __riscv_xlen == 64
+// Below "slli ((32+16)-N); srli (32+16)" for rv64
+UINT_EXT_USHORT_RSHIFT_N_UINT(1)
+UINT_EXT_USHORT_RSHIFT_N_UINT(7)
+UINT_EXT_USHORT_RSHIFT_N_UINT(8)
+UINT_EXT_USHORT_RSHIFT_N_UINT(9)
+UINT_EXT_USHORT_RSHIFT_N_UINT(15)
+// Below "srliw N" for rv64
+UINT_EXT_USHORT_RSHIFT_N_UINT(16)
+UINT_EXT_USHORT_RSHIFT_N_UINT(17)
+UINT_EXT_USHORT_RSHIFT_N_UINT(23)
+UINT_EXT_USHORT_RSHIFT_N_UINT(24)
+UINT_EXT_USHORT_RSHIFT_N_UINT(25)
+UINT_EXT_USHORT_RSHIFT_N_UINT(31)
+#endif /* __riscv_xlen == 64 */
+
+
+
+// Below "slli (16-N); srli 16" for rv32
+// Below "slli ((32+16)-N); srli (32+16)" for rv64
+UINT_EXT_USHORT_RSHIFT_N_ULONG(9)
+UINT_EXT_USHORT_RSHIFT_N_ULONG(15)
+
+
+
+// Below "slli (16-N); srli 16" for rv32
+// Below "slli ((32+16)-N); srli (32+16)" for rv64
+ULONG_EXT_USHORT_RSHIFT_N_UINT(9)
+ULONG_EXT_USHORT_RSHIFT_N_UINT(15)
+
+/* { dg-final { scan-assembler-times "slli\t" 9 { target { rv32 } } } } */
+/* { dg-final { scan-assembler-times "srli\t" 26 { target { rv32 } } } } */
+
+/* { dg-final { scan-assembler-times "slli\t" 36 { target { rv64 } } } } */
+/* { dg-final { scan-assembler-times "srli\t" 54 { target { rv64 } } } } */
+/* { dg-final { scan-assembler-times "srliw\t" 7 { target { rv64 } } } } */