LoongArch: Replace -mexplicit-relocs=auto simple-used address peephole2 with combine

The problem with peephole2 is it uses a naive sliding-window algorithm
and misses many cases.  For example:

    float a[10000];
    float t() { return a[0] + a[8000]; }

is compiled to:

    la.local    $r13,a
    la.local    $r12,a+32768
    fld.s       $f1,$r13,0
    fld.s       $f0,$r12,-768
    fadd.s      $f0,$f1,$f0

by trunk.  But as we've explained in r14-4851, the following would be
better with -mexplicit-relocs=auto:

    pcalau12i   $r13,%pc_hi20(a)
    pcalau12i   $r12,%pc_hi20(a+32000)
    fld.s       $f1,$r13,%pc_lo12(a)
    fld.s       $f0,$r12,%pc_lo12(a+32000)
    fadd.s      $f0,$f1,$f0

However the sliding-window algorithm just won't detect the pcalau12i/fld
pair to be optimized.  Use a define_insn_and_rewrite in combine pass
will work around the issue.

gcc/ChangeLog:

	* config/loongarch/predicates.md
	(symbolic_pcrel_offset_operand): New define_predicate.
	(mem_simple_ldst_operand): Likewise.
	* config/loongarch/loongarch-protos.h
	(loongarch_rewrite_mem_for_simple_ldst): Declare.
	* config/loongarch/loongarch.cc
	(loongarch_rewrite_mem_for_simple_ldst): Implement.
	* config/loongarch/loongarch.md (simple_load<mode>): New
	define_insn_and_rewrite.
	(simple_load_<su>ext<SUBDI:mode><GPR:mode>): Likewise.
	(simple_store<mode>): Likewise.
	(define_peephole2): Remove la.local/[f]ld peepholes.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/explicit-relocs-auto-single-load-store-2.c:
	New test.
	* gcc.target/loongarch/explicit-relocs-auto-single-load-store-3.c:
	New test.

6 files changed, 86 insertions, 87 deletions

diff --git a/gcc/config/loongarch/loongarch-protos.h b/gcc/config/loongarch/loongarch-protos.h
index 7bf21a4..024f311 100644
--- a/gcc/config/loongarch/loongarch-protos.h
+++ b/gcc/config/loongarch/loongarch-protos.h
@@ -163,6 +163,7 @@ extern bool loongarch_use_ins_ext_p (rtx, HOST_WIDE_INT, HOST_WIDE_INT);
 extern bool loongarch_check_zero_div_p (void);
 extern bool loongarch_pre_reload_split (void);
 extern int loongarch_use_bstrins_for_ior_with_mask (machine_mode, rtx *);
+extern rtx loongarch_rewrite_mem_for_simple_ldst (rtx);
 
 union loongarch_gen_fn_ptrs
 {
diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
index 1d4d8f0..9f2b3e9 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -5717,6 +5717,22 @@ loongarch_use_bstrins_for_ior_with_mask (machine_mode mode, rtx *op)
   return 0;
 }
 
+/* Rewrite a MEM for simple load/store under -mexplicit-relocs=auto
+   -mcmodel={normal/medium}.  */
+rtx
+loongarch_rewrite_mem_for_simple_ldst (rtx mem)
+{
+  rtx addr = XEXP (mem, 0);
+  rtx hi = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, addr),
+			   UNSPEC_PCALAU12I_GR);
+  rtx new_mem;
+
+  addr = gen_rtx_LO_SUM (Pmode, force_reg (Pmode, hi), addr);
+  new_mem = gen_rtx_MEM (GET_MODE (mem), addr);
+  MEM_COPY_ATTRIBUTES (new_mem, mem);
+  return new_mem;
+}
+
 /* Print the text for PRINT_OPERAND punctation character CH to FILE.
    The punctuation characters are:
 
diff --git a/gcc/config/loongarch/loongarch.md b/gcc/config/loongarch/loongarch.md
index e56ea71..d705717 100644
--- a/gcc/config/loongarch/loongarch.md
+++ b/gcc/config/loongarch/loongarch.md
@@ -4135,101 +4135,41 @@
 ;;
 ;; And if the pseudo op cannot be relaxed, we'll get a worse result (with
 ;; 3 instructions).
-(define_peephole2
-  [(set (match_operand:P 0 "register_operand")
-	(match_operand:P 1 "symbolic_pcrel_operand"))
-   (set (match_operand:LD_AT_LEAST_32_BIT 2 "register_operand")
-	(mem:LD_AT_LEAST_32_BIT (match_dup 0)))]
-  "la_opt_explicit_relocs == EXPLICIT_RELOCS_AUTO \
-   && (TARGET_CMODEL_NORMAL || TARGET_CMODEL_MEDIUM) \
-   && (peep2_reg_dead_p (2, operands[0]) \
-       || REGNO (operands[0]) == REGNO (operands[2]))"
-  [(set (match_dup 2)
-	(mem:LD_AT_LEAST_32_BIT (lo_sum:P (match_dup 0) (match_dup 1))))]
-  {
-    emit_insn (gen_pcalau12i_gr<P:mode> (operands[0], operands[1]));
-  })
-
-(define_peephole2
-  [(set (match_operand:P 0 "register_operand")
-	(match_operand:P 1 "symbolic_pcrel_operand"))
-   (set (match_operand:LD_AT_LEAST_32_BIT 2 "register_operand")
-	(mem:LD_AT_LEAST_32_BIT (plus (match_dup 0)
-				(match_operand 3 "const_int_operand"))))]
-  "la_opt_explicit_relocs == EXPLICIT_RELOCS_AUTO \
-   && (TARGET_CMODEL_NORMAL || TARGET_CMODEL_MEDIUM) \
-   && (peep2_reg_dead_p (2, operands[0]) \
-       || REGNO (operands[0]) == REGNO (operands[2]))"
-  [(set (match_dup 2)
-	(mem:LD_AT_LEAST_32_BIT (lo_sum:P (match_dup 0) (match_dup 1))))]
-  {
-    operands[1] = plus_constant (Pmode, operands[1], INTVAL (operands[3]));
-    emit_insn (gen_pcalau12i_gr<P:mode> (operands[0], operands[1]));
-  })
-
-(define_peephole2
-  [(set (match_operand:P 0 "register_operand")
-	(match_operand:P 1 "symbolic_pcrel_operand"))
-   (set (match_operand:GPR 2 "register_operand")
-	(any_extend:GPR (mem:SUBDI (match_dup 0))))]
-  "la_opt_explicit_relocs == EXPLICIT_RELOCS_AUTO \
-   && (TARGET_CMODEL_NORMAL || TARGET_CMODEL_MEDIUM) \
-   && (peep2_reg_dead_p (2, operands[0]) \
-       || REGNO (operands[0]) == REGNO (operands[2]))"
-  [(set (match_dup 2)
-	(any_extend:GPR (mem:SUBDI (lo_sum:P (match_dup 0)
-					     (match_dup 1)))))]
+(define_insn_and_rewrite "simple_load<mode>"
+  [(set (match_operand:LD_AT_LEAST_32_BIT 0 "register_operand" "=r,f")
+	(match_operand:LD_AT_LEAST_32_BIT 1 "mem_simple_ldst_operand" ""))]
+  "loongarch_pre_reload_split ()
+   && la_opt_explicit_relocs == EXPLICIT_RELOCS_AUTO
+   && (TARGET_CMODEL_NORMAL || TARGET_CMODEL_MEDIUM)"
+  "#"
+  "&& true"
   {
-    emit_insn (gen_pcalau12i_gr<P:mode> (operands[0], operands[1]));
+    operands[1] = loongarch_rewrite_mem_for_simple_ldst (operands[1]);
   })
 
-(define_peephole2
-  [(set (match_operand:P 0 "register_operand")
-	(match_operand:P 1 "symbolic_pcrel_operand"))
-   (set (match_operand:GPR 2 "register_operand")
+(define_insn_and_rewrite "simple_load_<su>ext<SUBDI:mode><GPR:mode>"
+  [(set (match_operand:GPR 0 "register_operand" "=r")
 	(any_extend:GPR
-	  (mem:SUBDI (plus (match_dup 0)
-			   (match_operand 3 "const_int_operand")))))]
-  "la_opt_explicit_relocs == EXPLICIT_RELOCS_AUTO \
-   && (TARGET_CMODEL_NORMAL || TARGET_CMODEL_MEDIUM) \
-   && (peep2_reg_dead_p (2, operands[0]) \
-       || REGNO (operands[0]) == REGNO (operands[2]))"
-  [(set (match_dup 2)
-	(any_extend:GPR (mem:SUBDI (lo_sum:P (match_dup 0)
-					     (match_dup 1)))))]
-  {
-    operands[1] = plus_constant (Pmode, operands[1], INTVAL (operands[3]));
-    emit_insn (gen_pcalau12i_gr<P:mode> (operands[0], operands[1]));
-  })
-
-(define_peephole2
-  [(set (match_operand:P 0 "register_operand")
-	(match_operand:P 1 "symbolic_pcrel_operand"))
-   (set (mem:ST_ANY (match_dup 0))
-	(match_operand:ST_ANY 2 "register_operand"))]
-  "la_opt_explicit_relocs == EXPLICIT_RELOCS_AUTO \
-   && (TARGET_CMODEL_NORMAL || TARGET_CMODEL_MEDIUM) \
-   && (peep2_reg_dead_p (2, operands[0])) \
-   && REGNO (operands[0]) != REGNO (operands[2])"
-  [(set (mem:ST_ANY (lo_sum:P (match_dup 0) (match_dup 1))) (match_dup 2))]
+	  (match_operand:SUBDI 1 "mem_simple_ldst_operand" "")))]
+  "loongarch_pre_reload_split ()
+   && la_opt_explicit_relocs == EXPLICIT_RELOCS_AUTO
+   && (TARGET_CMODEL_NORMAL || TARGET_CMODEL_MEDIUM)"
+  "#"
+  "&& true"
   {
-    emit_insn (gen_pcalau12i_gr<P:mode> (operands[0], operands[1]));
+    operands[1] = loongarch_rewrite_mem_for_simple_ldst (operands[1]);
   })
 
-(define_peephole2
-  [(set (match_operand:P 0 "register_operand")
-	(match_operand:P 1 "symbolic_pcrel_operand"))
-   (set (mem:ST_ANY (plus (match_dup 0)
-			  (match_operand 3 "const_int_operand")))
-	(match_operand:ST_ANY 2 "register_operand"))]
-  "la_opt_explicit_relocs == EXPLICIT_RELOCS_AUTO \
-   && (TARGET_CMODEL_NORMAL || TARGET_CMODEL_MEDIUM) \
-   && (peep2_reg_dead_p (2, operands[0])) \
-   && REGNO (operands[0]) != REGNO (operands[2])"
-  [(set (mem:ST_ANY (lo_sum:P (match_dup 0) (match_dup 1))) (match_dup 2))]
+(define_insn_and_rewrite "simple_store<mode>"
+  [(set (match_operand:ST_ANY 0 "mem_simple_ldst_operand" "")
+	(match_operand:ST_ANY 1 "reg_or_0_operand" "r,f"))]
+  "loongarch_pre_reload_split ()
+   && la_opt_explicit_relocs == EXPLICIT_RELOCS_AUTO
+   && (TARGET_CMODEL_NORMAL || TARGET_CMODEL_MEDIUM)"
+  "#"
+  "&& true"
   {
-    operands[1] = plus_constant (Pmode, operands[1], INTVAL (operands[3]));
-    emit_insn (gen_pcalau12i_gr<P:mode> (operands[0], operands[1]));
+    operands[0] = loongarch_rewrite_mem_for_simple_ldst (operands[0]);
   })
 
 ;; Synchronization instructions.
diff --git a/gcc/config/loongarch/predicates.md b/gcc/config/loongarch/predicates.md
index 83fea08..4db4442 100644
--- a/gcc/config/loongarch/predicates.md
+++ b/gcc/config/loongarch/predicates.md
@@ -579,6 +579,19 @@
   return loongarch_symbolic_constant_p (op, &type) && type == SYMBOL_PCREL;
 })
 
+(define_predicate "symbolic_pcrel_offset_operand"
+  (and (match_code "plus")
+       (match_operand 0 "symbolic_pcrel_operand")
+       (match_operand 1 "const_int_operand")))
+
+(define_predicate "mem_simple_ldst_operand"
+  (match_code "mem")
+{
+  op = XEXP (op, 0);
+  return (symbolic_pcrel_operand (op, Pmode)
+	  || symbolic_pcrel_offset_operand (op, Pmode));
+})
+
 (define_predicate "equality_operator"
   (match_code "eq,ne"))
 
diff --git a/gcc/testsuite/gcc.target/loongarch/explicit-relocs-auto-single-load-store-2.c b/gcc/testsuite/gcc.target/loongarch/explicit-relocs-auto-single-load-store-2.c
new file mode 100644
index 0000000..42cb966
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/explicit-relocs-auto-single-load-store-2.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=loongarch64 -mabi=lp64d -mexplicit-relocs=auto" } */
+
+float a[8001];
+float
+t (void)
+{
+  return a[0] + a[8000];
+}
+
+/* { dg-final { scan-assembler-not "la.local" } } */
diff --git a/gcc/testsuite/gcc.target/loongarch/explicit-relocs-auto-single-load-store-3.c b/gcc/testsuite/gcc.target/loongarch/explicit-relocs-auto-single-load-store-3.c
new file mode 100644
index 0000000..32aa538
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/explicit-relocs-auto-single-load-store-3.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mexplicit-relocs=auto -fdump-rtl-final" } */
+/* { dg-final { scan-rtl-dump-times "mem/v/c" 2 "final" } } */
+/* { dg-final { scan-assembler-not "la\\.local" } } */
+
+volatile unsigned long counter;
+
+unsigned long
+read (void)
+{
+  return counter;
+}
+
+void
+clear (void)
+{
+  counter = 0;
+}