RISC-V: Fix redundant vsetvl in fixed-vlmax vectorized codes[PR112326]

  With compile option --param=riscv-autovec-preference=fixed-vlmax, we have
redundant AVL/VL toggling:

	vsetvli	a5,a3,e8,mf4,ta,ma -> should be changed into e32m1
	vle32.v	v1,0(a1)
	vle32.v	v2,0(a0)
	vsetivli	zero,4,e32,m1,ta,ma -> redundant
	slli	a2,a5,2
	vadd.vv	v1,v1,v2
	sub	a3,a3,a5
	vsetvli	zero,a5,e32,m1,ta,ma -> redundant
	vse32.v	v1,0(a4)
	add	a0,a0,a2
	add	a1,a1,a2
	add	a4,a4,a2
	bne	a3,zero,.L3

The root cause is because we simplify AVL into immediate AVL too early
in FIXED-VLMAX situation. The later avlprop PASS failed to propagate AVL
generated by (SELECT_VL/vsetvl VL, AVL) into the normal RVV instruction.

So we need to remove immedate AVL simplification in 'expand' stage.

After this patch:

  	vsetvli	a5,a3,e32,m1,ta,ma
	slli	a2,a5,2
	vle32.v	v1,0(a1)
	vle32.v	v2,0(a0)
	sub	a3,a3,a5
	vadd.vv	v1,v1,v2
	vse32.v	v1,0(a4)
	add	a0,a0,a2
	add	a1,a1,a2
	add	a4,a4,a2
	bne	a3,zero,.L3

After the removed simplification, the following situation should be fixed:
typedef int8_t vnx2qi __attribute__ ((vector_size (2)));

__attribute__ ((noipa)) void
f_vnx2qi (int8_t a, int8_t b, int8_t *out)
{
  vnx2qi v = {a, b};
  *(vnx2qi *) out = v;
}

We should use vsetvili zero, 2 instead of vsetvl a5,zero.
Such simplification is done in avlprop PASS which is also included in this patch
to fix regression of these situation.

	PR target/112326

gcc/ChangeLog:

	* config/riscv/riscv-avlprop.cc (get_insn_vtype_mode): New function.
	(simplify_replace_vlmax_avl): Ditto.
	(pass_avlprop::execute): Add immediate AVL simplification.
	* config/riscv/riscv-protos.h (imm_avl_p): Rename.
	* config/riscv/riscv-v.cc (const_vlmax_p): Ditto.
	(imm_avl_p): Ditto.
	(emit_vlmax_insn): Adapt for new interface name.
	* config/riscv/vector.md (mode_idx): New attribute.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/pr112326.c: New test.

---
 gcc/config/riscv/riscv-avlprop.cc             | 76 +++++++++++++++----
 gcc/config/riscv/riscv-protos.h               |  1 +
 gcc/config/riscv/riscv-v.cc                   | 24 ++----
 gcc/config/riscv/vector.md                    | 29 ++++++-
 .../gcc.target/riscv/rvv/autovec/pr112326.c   | 16 ++++
 5 files changed, 113 insertions(+), 33 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr112326.c
  

update with more dump information in V2:
https://gcc.gnu.org/pipermail/gcc-patches/2023-November/634950.html 




juzhe.zhong@rivai.ai
 
From: Juzhe-Zhong
Date: 2023-11-02 11:06
To: gcc-patches
CC: kito.cheng; kito.cheng; jeffreyalaw; rdapp.gcc; Juzhe-Zhong
Subject: [PATCH] RISC-V: Fix redundant vsetvl in fixed-vlmax vectorized codes[PR112326]
With compile option --param=riscv-autovec-preference=fixed-vlmax, we have
redundant AVL/VL toggling:
 
vsetvli a5,a3,e8,mf4,ta,ma -> should be changed into e32m1
vle32.v v1,0(a1)
vle32.v v2,0(a0)
vsetivli zero,4,e32,m1,ta,ma -> redundant
slli a2,a5,2
vadd.vv v1,v1,v2
sub a3,a3,a5
vsetvli zero,a5,e32,m1,ta,ma -> redundant
vse32.v v1,0(a4)
add a0,a0,a2
add a1,a1,a2
add a4,a4,a2
bne a3,zero,.L3
 
The root cause is because we simplify AVL into immediate AVL too early
in FIXED-VLMAX situation. The later avlprop PASS failed to propagate AVL
generated by (SELECT_VL/vsetvl VL, AVL) into the normal RVV instruction.
 
So we need to remove immedate AVL simplification in 'expand' stage.
 
After this patch:
 
  vsetvli a5,a3,e32,m1,ta,ma
slli a2,a5,2
vle32.v v1,0(a1)
vle32.v v2,0(a0)
sub a3,a3,a5
vadd.vv v1,v1,v2
vse32.v v1,0(a4)
add a0,a0,a2
add a1,a1,a2
add a4,a4,a2
bne a3,zero,.L3
 
After the removed simplification, the following situation should be fixed:
typedef int8_t vnx2qi __attribute__ ((vector_size (2)));
 
__attribute__ ((noipa)) void
f_vnx2qi (int8_t a, int8_t b, int8_t *out)
{
  vnx2qi v = {a, b};
  *(vnx2qi *) out = v;
}
 
We should use vsetvili zero, 2 instead of vsetvl a5,zero.
Such simplification is done in avlprop PASS which is also included in this patch
to fix regression of these situation.
 
PR target/112326
 
gcc/ChangeLog:
 
* config/riscv/riscv-avlprop.cc (get_insn_vtype_mode): New function.
(simplify_replace_vlmax_avl): Ditto.
(pass_avlprop::execute): Add immediate AVL simplification.
* config/riscv/riscv-protos.h (imm_avl_p): Rename.
* config/riscv/riscv-v.cc (const_vlmax_p): Ditto.
(imm_avl_p): Ditto.
(emit_vlmax_insn): Adapt for new interface name.
* config/riscv/vector.md (mode_idx): New attribute.
 
gcc/testsuite/ChangeLog:
 
* gcc.target/riscv/rvv/autovec/pr112326.c: New test.
 
---
gcc/config/riscv/riscv-avlprop.cc             | 76 +++++++++++++++----
gcc/config/riscv/riscv-protos.h               |  1 +
gcc/config/riscv/riscv-v.cc                   | 24 ++----
gcc/config/riscv/vector.md                    | 29 ++++++-
.../gcc.target/riscv/rvv/autovec/pr112326.c   | 16 ++++
5 files changed, 113 insertions(+), 33 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr112326.c
 
diff --git a/gcc/config/riscv/riscv-avlprop.cc b/gcc/config/riscv/riscv-avlprop.cc
index c59eb7f6fa3..e4d14a89a91 100644
--- a/gcc/config/riscv/riscv-avlprop.cc
+++ b/gcc/config/riscv/riscv-avlprop.cc
@@ -109,6 +109,36 @@ vlmax_ta_p (rtx_insn *rinsn)
   return vlmax_avl_type_p (rinsn) && tail_agnostic_p (rinsn);
}
+static machine_mode
+get_insn_vtype_mode (rtx_insn *rinsn)
+{
+  extract_insn_cached (rinsn);
+  int mode_idx = get_attr_mode_idx (rinsn);
+  gcc_assert (mode_idx != INVALID_ATTRIBUTE);
+  return GET_MODE (recog_data.operand[mode_idx]);
+}
+
+static void
+simplify_replace_vlmax_avl (rtx_insn *rinsn, rtx new_avl)
+{
+  /* Replace AVL operand.  */
+  extract_insn_cached (rinsn);
+  rtx avl = recog_data.operand[get_attr_vl_op_idx (rinsn)];
+  int count = count_regno_occurrences (rinsn, REGNO (avl));
+  gcc_assert (count == 1);
+  rtx new_pat = simplify_replace_rtx (PATTERN (rinsn), avl, new_avl);
+  validate_change_or_fail (rinsn, &PATTERN (rinsn), new_pat, false);
+
+  /* Change AVL TYPE into NONVLMAX if it is VLMAX.  */
+  if (vlmax_avl_type_p (rinsn))
+    {
+      int index = get_attr_avl_type_idx (rinsn);
+      gcc_assert (index != INVALID_ATTRIBUTE);
+      validate_change_or_fail (rinsn, recog_data.operand_loc[index],
+        get_avl_type_rtx (avl_type::NONVLMAX), false);
+    }
+}
+
const pass_data pass_data_avlprop = {
   RTL_PASS, /* type */
   "avlprop", /* name */
@@ -385,22 +415,7 @@ pass_avlprop::execute (function *fn)
  print_rtl_single (dump_file, rinsn);
}
       /* Replace AVL operand.  */
-      extract_insn_cached (rinsn);
-      rtx avl = recog_data.operand[get_attr_vl_op_idx (rinsn)];
-      int count = count_regno_occurrences (rinsn, REGNO (avl));
-      gcc_assert (count == 1);
-      rtx new_pat = simplify_replace_rtx (PATTERN (rinsn), avl, prop.second);
-      validate_change_or_fail (rinsn, &PATTERN (rinsn), new_pat, false);
-
-      /* Change AVL TYPE into NONVLMAX if it is VLMAX.  */
-      if (vlmax_avl_type_p (rinsn))
- {
-   int index = get_attr_avl_type_idx (rinsn);
-   gcc_assert (index != INVALID_ATTRIBUTE);
-   validate_change_or_fail (rinsn, recog_data.operand_loc[index],
-    get_avl_type_rtx (avl_type::NONVLMAX),
-    false);
- }
+      simplify_replace_vlmax_avl (rinsn, prop.second);
       if (dump_file && (dump_flags & TDF_DETAILS))
{
  fprintf (dump_file, "Successfully to match this instruction: ");
@@ -408,6 +423,35 @@ pass_avlprop::execute (function *fn)
}
     }
+  if (riscv_autovec_preference == RVV_FIXED_VLMAX)
+    {
+      /* Simplify VLMAX AVL into immediate AVL.
+ E.g. Simplify this following case:
+
+       vsetvl a5, zero, e32, m1
+       vadd.vv
+
+     into:
+
+       vsetvl zero, 4, e32, m1
+       vadd.vv
+ if GET_MODE_NUNITS (RVVM1SImode) == 4.  */
+      if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "\nSimplifying VLMAX AVL into IMM AVL\n\n");
+      for (auto &candidate : m_candidates)
+ {
+   rtx_insn *rinsn = candidate.second->rtl ();
+   machine_mode vtype_mode = get_insn_vtype_mode (rinsn);
+   if (candidate.first == AVLPROP_VLMAX_TA
+       && !m_avl_propagations->get (candidate.second)
+       && imm_avl_p (vtype_mode))
+     {
+       rtx new_avl = gen_int_mode (GET_MODE_NUNITS (vtype_mode), Pmode);
+       simplify_replace_vlmax_avl (rinsn, new_avl);
+     }
+ }
+    }
+
   avlprop_done ();
   return 0;
}
diff --git a/gcc/config/riscv/riscv-protos.h b/gcc/config/riscv/riscv-protos.h
index 02056591ec6..6a0c59bd63f 100644
--- a/gcc/config/riscv/riscv-protos.h
+++ b/gcc/config/riscv/riscv-protos.h
@@ -593,6 +593,7 @@ bool vlmax_avl_p (rtx);
uint8_t get_sew (rtx_insn *);
enum vlmul_type get_vlmul (rtx_insn *);
int count_regno_occurrences (rtx_insn *, unsigned int);
+bool imm_avl_p (machine_mode);
}
/* We classify builtin types into two classes:
diff --git a/gcc/config/riscv/riscv-v.cc b/gcc/config/riscv/riscv-v.cc
index 668f3cd706b..679f922bc20 100644
--- a/gcc/config/riscv/riscv-v.cc
+++ b/gcc/config/riscv/riscv-v.cc
@@ -55,17 +55,17 @@ using namespace riscv_vector;
namespace riscv_vector {
-/* Return true if vlmax is constant value and can be used in vsetivl.  */
-static bool
-const_vlmax_p (machine_mode mode)
+/* Return true if NUNTIS <=31 so that we can use immediate AVL in vsetivli.  */
+bool
+imm_avl_p (machine_mode mode)
{
   poly_uint64 nuints = GET_MODE_NUNITS (mode);
   return nuints.is_constant ()
-    /* The vsetivli can only hold register 0~31.  */
-    ? (IN_RANGE (nuints.to_constant (), 0, 31))
-    /* Only allowed in VLS-VLMAX mode.  */
-    : false;
+    /* The vsetivli can only hold register 0~31.  */
+    ? (IN_RANGE (nuints.to_constant (), 0, 31))
+    /* Only allowed in VLS-VLMAX mode.  */
+    : false;
}
/* Helper functions for insn_flags && insn_types */
@@ -298,14 +298,6 @@ public:
      len = force_reg (Pmode, len);
    vls_p = true;
  }
- else if (const_vlmax_p (vtype_mode))
-   {
-     /* Optimize VLS-VLMAX code gen, we can use vsetivli instead of
-        the vsetvli to obtain the value of vlmax.  */
-     poly_uint64 nunits = GET_MODE_NUNITS (vtype_mode);
-     len = gen_int_mode (nunits, Pmode);
-     vls_p = true;
-   }
else if (can_create_pseudo_p ())
  {
    len = gen_reg_rtx (Pmode);
@@ -370,7 +362,7 @@ void
emit_vlmax_insn (unsigned icode, unsigned insn_flags, rtx *ops)
{
   insn_expander<RVV_INSN_OPERANDS_MAX> e (insn_flags, true);
-  gcc_assert (can_create_pseudo_p () || const_vlmax_p (e.get_vtype_mode (ops)));
+  gcc_assert (can_create_pseudo_p () || imm_avl_p (e.get_vtype_mode (ops)));
   e.emit_insn ((enum insn_code) icode, ops);
}
diff --git a/gcc/config/riscv/vector.md b/gcc/config/riscv/vector.md
index a1a78120525..28baee59a9b 100644
--- a/gcc/config/riscv/vector.md
+++ b/gcc/config/riscv/vector.md
@@ -708,6 +708,32 @@
       (const_int 5)]
(const_int INVALID_ATTRIBUTE)))
+;; The index of operand[] represents the machine mode of the instruction.
+(define_attr "mode_idx" ""
+ (cond [(eq_attr "type" "vlde,vste,vldm,vstm,vlds,vsts,vldux,vldox,vldff,vldr,vstr,\
+ vlsegde,vlsegds,vlsegdux,vlsegdox,vlsegdff,vialu,vext,vicalu,\
+ vshift,vicmp,viminmax,vimul,vidiv,vimuladd,vimerge,vimov,\
+ vsalu,vaalu,vsmul,vsshift,vfalu,vfmul,vfdiv,vfmuladd,vfsqrt,vfrecp,\
+ vfcmp,vfminmax,vfsgnj,vfclass,vfmerge,vfmov,\
+ vfcvtitof,vfncvtitof,vfncvtftoi,vfncvtftof,vmalu,vmiota,vmidx,\
+ vimovxv,vfmovfv,vslideup,vslidedown,vislide1up,vislide1down,vfslide1up,vfslide1down,\
+ vgather,vcompress,vmov")
+        (const_int 0)
+
+        (eq_attr "type" "vimovvx,vfmovvf")
+        (const_int 1)
+
+        (eq_attr "type" "vssegte,vnshift,vmpop,vmffs")
+        (const_int 2)       
+
+        (eq_attr "type" "vstux,vstox,vssegts,vssegtux,vssegtox,vfcvtftoi,vfwcvtitof,vfwcvtftoi,
+ vfwcvtftof,vmsfs,vired,viwred,vfredu,vfredo,vfwredu,vfwredo")
+        (const_int 3)
+
+        (eq_attr "type" "viwalu,viwmul,viwmuladd,vnclip,vfwalu,vfwmul,vfwmuladd")
+        (const_int 4)]
+ (const_int INVALID_ATTRIBUTE)))
+
;; The index of operand[] to get the avl op.
(define_attr "vl_op_idx" ""
   (cond [(eq_attr "type" "vlde,vste,vimov,vfmov,vldm,vstm,vmalu,vsts,vstux,\
@@ -1207,7 +1233,8 @@
   }
   [(set_attr "type" "vmov,vlde,vste")
    (set_attr "mode" "<VT:MODE>")
-   (set (attr "avl_type_idx") (const_int INVALID_ATTRIBUTE))])
+   (set (attr "avl_type_idx") (const_int INVALID_ATTRIBUTE))
+   (set (attr "mode_idx") (const_int INVALID_ATTRIBUTE))])
;; -----------------------------------------------------------------
;; ---- VLS Moves Operations
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr112326.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr112326.c
new file mode 100644
index 00000000000..2ad50139cb2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr112326.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fno-vect-cost-model --param=riscv-autovec-preference=fixed-vlmax" } */
+
+void
+f (int *__restrict y, int *__restrict x, int *__restrict z, int n)
+{
+  for (int i = 0; i < n; ++i)
+    x[i] = y[i] + x[i];
+}
+
+/* { dg-final { scan-assembler-times {vsetvli} 1 } } */
+/* { dg-final { scan-assembler-not {vsetivli} } } */
+/* { dg-final { scan-assembler-times {vsetvli\s*[a-x0-9]+,\s*[a-x0-9]+} 1 } } */
+/* { dg-final { scan-assembler-not {vsetvli\s*[a-x0-9]+,\s*zero} } } */
+/* { dg-final { scan-assembler-not {vsetvli\s*zero} } } */
+/* { dg-final { scan-assembler-not {vsetivli\s*zero} } } */
-- 
2.36.3