[COMMITTED,GCC9] Backport RISC-V: Fix bad insn splits with paradoxical subregs.
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Message ID CA+yXCZC8KVwQ-XR=6=1A7+aRbZUOXw_WevB4NFSKr5ctKP5C+g@mail.gmail.com
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  • [COMMITTED,GCC9] Backport RISC-V: Fix bad insn splits with paradoxical subregs.
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Kito Cheng Sept. 19, 2019, 6:43 a.m. UTC
This patch fix PR target/91635, fixing wrong code gen for RISC-V.

Patch
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From 52e32e2f82b4fe09c253e230c4fe321a0341aae7 Mon Sep 17 00:00:00 2001
From: kito <kito@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Thu, 19 Sep 2019 06:38:23 +0000
Subject: [PATCH] RISC-V: Fix bad insn splits with paradoxical subregs.

Shifting by more than the size of a SUBREG_REG doesn't work, so we either
need to disable splits if an input is paradoxical, or else we need to
generate a clean temporary for intermediate results.

Jakub wrote the first version of this patch, so gets primary credit for it.

	gcc/
	PR target/91635
	* config/riscv/riscv.md (zero_extendsidi2, zero_extendhi<GPR:mode>2,
	extend<SHORT:mode><SUPERQI:mode>2): Don't split if
	paradoxical_subreg_p (operands[0]).
	(*lshrsi3_zero_extend_3+1, *lshrsi3_zero_extend_3+2): Add clobber and
	use as intermediate value.

	gcc/testsuite/
	PR target/91635
	* gcc.c-torture/execute/pr91635.c: New test.
	* gcc.target/riscv/shift-shift-4.c: New test.
	* gcc.target/riscv/shift-shift-5.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-9-branch@275929 138bc75d-0d04-0410-961f-82ee72b054a4
---
 gcc/ChangeLog                                 | 13 +++++
 gcc/config/riscv/riscv.md                     | 30 +++++++---
 gcc/testsuite/ChangeLog                       | 11 ++++
 gcc/testsuite/gcc.c-torture/execute/pr91635.c | 57 +++++++++++++++++++
 .../gcc.target/riscv/shift-shift-4.c          | 13 +++++
 .../gcc.target/riscv/shift-shift-5.c          | 16 ++++++
 6 files changed, 131 insertions(+), 9 deletions(-)
 create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr91635.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/shift-shift-4.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/shift-shift-5.c

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 95f978d5805..aa90ce5df7b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@ 
+2019-09-19  Kito Cheng  <kito.cheng@sifive.com>
+
+	Backport from mainline
+	2019-09-05  Jakub Jelinek  <jakub@redhat.com>
+		    Jim Wilson  <jimw@sifive.com>
+
+	PR target/91635
+	* config/riscv/riscv.md (zero_extendsidi2, zero_extendhi<GPR:mode>2,
+	extend<SHORT:mode><SUPERQI:mode>2): Don't split if
+	paradoxical_subreg_p (operands[0]).
+	(*lshrsi3_zero_extend_3+1, *lshrsi3_zero_extend_3+2): Add clobber and
+	use as intermediate value.
+
 2019-09-11  Eric Botcazou  <ebotcazou@adacore.com>
 
 	PR rtl-optimization/89795
diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index a8bac170e72..7850c41f3c7 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -1051,7 +1051,9 @@ 
   "@
    #
    lwu\t%0,%1"
-  "&& reload_completed && REG_P (operands[1])"
+  "&& reload_completed
+   && REG_P (operands[1])
+   && !paradoxical_subreg_p (operands[0])"
   [(set (match_dup 0)
 	(ashift:DI (match_dup 1) (const_int 32)))
    (set (match_dup 0)
@@ -1068,7 +1070,9 @@ 
   "@
    #
    lhu\t%0,%1"
-  "&& reload_completed && REG_P (operands[1])"
+  "&& reload_completed
+   && REG_P (operands[1])
+   && !paradoxical_subreg_p (operands[0])"
   [(set (match_dup 0)
 	(ashift:GPR (match_dup 1) (match_dup 2)))
    (set (match_dup 0)
@@ -1117,7 +1121,9 @@ 
   "@
    #
    l<SHORT:size>\t%0,%1"
-  "&& reload_completed && REG_P (operands[1])"
+  "&& reload_completed
+   && REG_P (operands[1])
+   && !paradoxical_subreg_p (operands[0])"
   [(set (match_dup 0) (ashift:SI (match_dup 1) (match_dup 2)))
    (set (match_dup 0) (ashiftrt:SI (match_dup 0) (match_dup 2)))]
 {
@@ -1765,15 +1771,20 @@ 
 ;; 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.
+
+;; Generating a temporary for the shift output gives better combiner results;
+;; and also fixes a problem where op0 could be a paradoxical reg and shifting
+;; by amounts larger than the size of the SUBREG_REG doesn't work.
 (define_split
   [(set (match_operand:GPR 0 "register_operand")
 	(and:GPR (match_operand:GPR 1 "register_operand")
-		 (match_operand:GPR 2 "p2m1_shift_operand")))]
+		 (match_operand:GPR 2 "p2m1_shift_operand")))
+   (clobber (match_operand:GPR 3 "register_operand"))]
   ""
- [(set (match_dup 0)
+ [(set (match_dup 3)
        (ashift:GPR (match_dup 1) (match_dup 2)))
   (set (match_dup 0)
-       (lshiftrt:GPR (match_dup 0) (match_dup 2)))]
+       (lshiftrt:GPR (match_dup 3) (match_dup 2)))]
 {
   /* Op2 is a VOIDmode constant, so get the mode size from op1.  */
   operands[2] = GEN_INT (GET_MODE_BITSIZE (GET_MODE (operands[1]))
@@ -1785,12 +1796,13 @@ 
 (define_split
   [(set (match_operand:DI 0 "register_operand")
 	(and:DI (match_operand:DI 1 "register_operand")
-		(match_operand:DI 2 "high_mask_shift_operand")))]
+		(match_operand:DI 2 "high_mask_shift_operand")))
+   (clobber (match_operand:DI 3 "register_operand"))]
   "TARGET_64BIT"
-  [(set (match_dup 0)
+  [(set (match_dup 3)
 	(lshiftrt:DI (match_dup 1) (match_dup 2)))
    (set (match_dup 0)
-	(ashift:DI (match_dup 0) (match_dup 2)))]
+	(ashift:DI (match_dup 3) (match_dup 2)))]
 {
   operands[2] = GEN_INT (ctz_hwi (INTVAL (operands[2])));
 })
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index cd500d0b1c7..2c6127fa526 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,14 @@ 
+2019-09-19  Kito Cheng  <kito.cheng@sifive.com>
+
+	Backport from mainline
+	2019-09-05  Jakub Jelinek  <jakub@redhat.com>
+		    Jim Wilson  <jimw@sifive.com>
+
+	PR target/91635
+	* gcc.c-torture/execute/pr91635.c: New test.
+	* gcc.target/riscv/shift-shift-4.c: New test.
+	* gcc.target/riscv/shift-shift-5.c: New test.
+
 2019-09-18  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	Backport from trunk
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr91635.c b/gcc/testsuite/gcc.c-torture/execute/pr91635.c
new file mode 100644
index 00000000000..878a491fc36
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr91635.c
@@ -0,0 +1,57 @@ 
+/* PR target/91635 */
+
+#if __CHAR_BIT__ == 8 && __SIZEOF_SHORT__ == 2 \
+    && __SIZEOF_INT__ == 4 && __SIZEOF_LONG_LONG__ == 8
+unsigned short b, c;
+int u, v, w, x;
+
+__attribute__ ((noipa)) int
+foo (unsigned short c)
+{
+  c <<= __builtin_add_overflow (-c, -1, &b);
+  c >>= 1;
+  return c;
+}
+
+__attribute__ ((noipa)) int
+bar (unsigned short b)
+{
+  b <<= -14 & 15;
+  b = b >> -~1;
+  return b;
+}
+
+__attribute__ ((noipa)) int
+baz (unsigned short e)
+{
+  e <<= 1;
+  e >>= __builtin_add_overflow (8719476735, u, &v);
+  return e;
+}
+
+__attribute__ ((noipa)) int
+qux (unsigned int e)
+{
+  c = ~1;
+  c *= e;
+  c = c >> (-15 & 5);
+  return c + w + x;
+}
+#endif
+
+int
+main ()
+{
+#if __CHAR_BIT__ == 8 && __SIZEOF_SHORT__ == 2 \
+    && __SIZEOF_INT__ == 4 && __SIZEOF_LONG_LONG__ == 8
+  if (foo (0xffff) != 0x7fff)
+    __builtin_abort ();
+  if (bar (5) != 5)
+    __builtin_abort ();
+  if (baz (~0) != 0x7fff)
+    __builtin_abort ();
+  if (qux (2) != 0x7ffe)
+    __builtin_abort ();
+#endif
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/riscv/shift-shift-4.c b/gcc/testsuite/gcc.target/riscv/shift-shift-4.c
new file mode 100644
index 00000000000..72a45ee87ae
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/shift-shift-4.c
@@ -0,0 +1,13 @@ 
+/* { dg-do compile } */
+/* { dg-options "-march=rv32i -mabi=ilp32 -O2" } */
+
+/* One zero-extend shift can be eliminated by modifying the constant in the
+   greater than test.  Started working after modifying the splitter
+   lshrsi3_zero_extend_3+1 to use a temporary reg for the first split dest.  */
+int
+sub (int i)
+{
+  i &= 0x7fffffff;
+  return i > 0x7f800000;
+}
+/* { dg-final { scan-assembler-not "srli" } } */
diff --git a/gcc/testsuite/gcc.target/riscv/shift-shift-5.c b/gcc/testsuite/gcc.target/riscv/shift-shift-5.c
new file mode 100644
index 00000000000..5b2ae89a471
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/shift-shift-5.c
@@ -0,0 +1,16 @@ 
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc -mabi=lp64d -O2" } */
+
+/* Fails if lshrsi3_zero_extend_3+1 uses a temp reg which has no REG_DEST
+   note.  */
+unsigned long
+sub (long l)
+{
+  union u {
+    struct s { int a : 19; unsigned int b : 13; int x; } s;
+    long l;
+  } u;
+  u.l = l;
+  return u.s.b;
+}
+/* { dg-final { scan-assembler "srliw" } } */
-- 
2.17.1