[gcc r12-7486] LRA, rs6000, Darwin: Revise lo_sum use for forced constants [PR104117].

[Iain D Sandoe <iains@gcc.gnu.org>]

https://gcc.gnu.org/g:f1b3e3853329b58fb2e50c17487df2ecbc4a5608

commit r12-7486-gf1b3e3853329b58fb2e50c17487df2ecbc4a5608
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Wed Feb 23 13:53:44 2022 +0000

    LRA, rs6000, Darwin: Revise lo_sum use for forced constants [PR104117].
    
    Follow up discussion to the initial patch for this PR identified that it is
    preferable to avoid the LRA change, and arrange for the target to reject the
    hi and lo_sum selections when presented with an invalid address.
    
    We split the Darwin high/low selectors into two:
     1. One that handles non-PIC addresses (kernel mode, mdynamic-no-pic).
     2. One that handles PIC addresses and rejects SYMBOL_REFs unless they are
        suitably wrapped in the MACHOPIC_OFFSET unspec.
    
    The second case is handled by providing a new predicate (macho_pic_address)
    that checks the requirements.
    
    Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
    
            PR target/104117
    
    gcc/ChangeLog:
    
            * config/rs6000/darwin.md (@machopic_high_<mode>): New.
            (@machopic_low_<mode>): New.
            * config/rs6000/predicates.md (macho_pic_address): New.
            * config/rs6000/rs6000.cc (rs6000_legitimize_address): Do not
            apply the TLS processing to Darwin.
            * lra-constraints.cc (process_address_1): Revert the changes
            in r12-7209.

Diff:
---
 gcc/config/rs6000/darwin.md     | 19 +++++++++++++++----
 gcc/config/rs6000/predicates.md | 14 ++++++++++++++
 gcc/config/rs6000/rs6000.cc     |  2 +-
 gcc/lra-constraints.cc          | 17 +++++++++++++++--
 4 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/gcc/config/rs6000/darwin.md b/gcc/config/rs6000/darwin.md
index 8443585df00..e73d59e8066 100644
--- a/gcc/config/rs6000/darwin.md
+++ b/gcc/config/rs6000/darwin.md
@@ -121,21 +121,32 @@ You should have received a copy of the GNU General Public License
    stw %0,lo16(%2)(%1)"
   [(set_attr "type" "store")])
 
-;; 64-bit MachO load/store support
-
 ;; Mach-O PIC.
 
 (define_insn "@macho_high_<mode>"
   [(set (match_operand:P 0 "gpc_reg_operand" "=b*r")
 	(high:P (match_operand 1 "" "")))]
-  "TARGET_MACHO && (DEFAULT_ABI == ABI_DARWIN)"
+  "TARGET_MACHO && (DEFAULT_ABI == ABI_DARWIN) && !flag_pic"
   "lis %0,ha16(%1)")
 
 (define_insn "@macho_low_<mode>"
   [(set (match_operand:P 0 "gpc_reg_operand" "=r")
 	(lo_sum:P (match_operand:P 1 "gpc_reg_operand" "b")
 		   (match_operand 2 "" "")))]
-   "TARGET_MACHO && (DEFAULT_ABI == ABI_DARWIN)"
+   "TARGET_MACHO && (DEFAULT_ABI == ABI_DARWIN) && !flag_pic"
+   "la %0,lo16(%2)(%1)")
+
+(define_insn "@machopic_high_<mode>"
+  [(set (match_operand:P 0 "gpc_reg_operand" "=b*r")
+	(high:P (match_operand 1 "macho_pic_address" "")))]
+  "TARGET_MACHO && flag_pic"
+  "lis %0,ha16(%1)")
+
+(define_insn "@machopic_low_<mode>"
+  [(set (match_operand:P 0 "gpc_reg_operand" "=r")
+	(lo_sum:P (match_operand:P 1 "gpc_reg_operand" "b")
+		   (match_operand 2 "macho_pic_address" "")))]
+   "TARGET_MACHO && flag_pic"
    "la %0,lo16(%2)(%1)")
 
 (define_split
diff --git a/gcc/config/rs6000/predicates.md b/gcc/config/rs6000/predicates.md
index c65dfb91f3d..28f6e9883cb 100644
--- a/gcc/config/rs6000/predicates.md
+++ b/gcc/config/rs6000/predicates.md
@@ -2045,3 +2045,17 @@
  (if_then_else (match_test "TARGET_VSX")
   (match_operand 0 "reg_or_cint_operand")
   (match_operand 0 "const_int_operand")))
+
+;; Return true if the operand is a valid Mach-O pic address.
+;;
+(define_predicate "macho_pic_address"
+  (match_code "const,unspec")
+{
+  if (GET_CODE (op) == CONST)
+    op = XEXP (op, 0);
+
+  if (GET_CODE (op) == UNSPEC && XINT (op, 1) == UNSPEC_MACHOPIC_OFFSET)
+    return CONSTANT_P (XVECEXP (op, 0, 0));
+  else
+    return false;
+})
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 5b100a8f2fb..2388d44c8cc 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -9021,7 +9021,7 @@ rs6000_legitimize_address (rtx x, rtx oldx ATTRIBUTE_UNUSED,
       else
 	return force_reg (Pmode, x);
     }
-  if (SYMBOL_REF_P (x))
+  if (SYMBOL_REF_P (x) && !TARGET_MACHO)
     {
       enum tls_model model = SYMBOL_REF_TLS_MODEL (x);
       if (model != 0)
diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index 5cd89e7eedd..080b44ad87a 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -3625,8 +3625,21 @@ process_address_1 (int nop, bool check_only_p,
 		  *ad.inner = gen_rtx_LO_SUM (Pmode, new_reg, addr);
 		  if (!valid_address_p (op, &ad, cn))
 		    {
-		      *ad.inner = addr; /* Punt.  */
-		      code = -1;
+		      /* Try to put lo_sum into register.  */
+		      insn = emit_insn (gen_rtx_SET
+					(new_reg,
+					 gen_rtx_LO_SUM (Pmode, new_reg, addr)));
+		      code = recog_memoized (insn);
+		      if (code >= 0)
+			{
+			  *ad.inner = new_reg;
+			  if (!valid_address_p (op, &ad, cn))
+			    {
+			      *ad.inner = addr;
+			      code = -1;
+			    }
+			}
+
 		    }
 		}
 	      if (code < 0)