rs6000: Wrap diff of immediates in const (PR83629)

In various of our 32-bit load_toc patterns we take the difference of
two immediates (labels) as a term to something bigger; but this isn't
canonical RTL, it needs to be wrapped in CONST.


	PR target/83629
	* config/rs6000/rs6000.md (load_toc_v4_PIC_2, load_toc_v4_PIC_3b,
	load_toc_v4_PIC_3c): Wrap const term in CONST RTL.

testsuite/
	PR target/83629
	* gcc.target/powerpc/pr83629.c: New testcase.

From-SVN: r256432

gcc/ChangeLog

+2018-01-10  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR target/83629
+	* config/rs6000/rs6000.md (load_toc_v4_PIC_2, load_toc_v4_PIC_3b,
+	load_toc_v4_PIC_3c): Wrap const term in CONST RTL.
+
 2018-01-10  Richard Biener  <rguenther@suse.de>
 
 	PR debug/83765

gcc/config/rs6000/rs6000.md

@@ -10646,27 +10646,33 @@
 
 (define_insn "load_toc_v4_PIC_2"
   [(set (match_operand:SI 0 "gpc_reg_operand" "=r")
-	(mem:SI (plus:SI (match_operand:SI 1 "gpc_reg_operand" "b")
-		   (minus:SI (match_operand:SI 2 "immediate_operand" "s")
-			     (match_operand:SI 3 "immediate_operand" "s")))))]
+	(mem:SI (plus:SI
+		  (match_operand:SI 1 "gpc_reg_operand" "b")
+		  (const
+		    (minus:SI (match_operand:SI 2 "immediate_operand" "s")
+			      (match_operand:SI 3 "immediate_operand" "s"))))))]
   "TARGET_ELF && DEFAULT_ABI == ABI_V4 && flag_pic == 2"
   "lwz %0,%2-%3(%1)"
   [(set_attr "type" "load")])
 
 (define_insn "load_toc_v4_PIC_3b"
   [(set (match_operand:SI 0 "gpc_reg_operand" "=r")
-	(plus:SI (match_operand:SI 1 "gpc_reg_operand" "b")
-		 (high:SI
-		   (minus:SI (match_operand:SI 2 "symbol_ref_operand" "s")
-			     (match_operand:SI 3 "symbol_ref_operand" "s")))))]
+	(plus:SI
+	  (match_operand:SI 1 "gpc_reg_operand" "b")
+	  (high:SI
+	    (const
+	      (minus:SI (match_operand:SI 2 "symbol_ref_operand" "s")
+			(match_operand:SI 3 "symbol_ref_operand" "s"))))))]
   "TARGET_ELF && TARGET_SECURE_PLT && DEFAULT_ABI == ABI_V4 && flag_pic"
   "addis %0,%1,%2-%3@ha")
 
 (define_insn "load_toc_v4_PIC_3c"
   [(set (match_operand:SI 0 "gpc_reg_operand" "=r")
-	(lo_sum:SI (match_operand:SI 1 "gpc_reg_operand" "b")
-		   (minus:SI (match_operand:SI 2 "symbol_ref_operand" "s")
-			     (match_operand:SI 3 "symbol_ref_operand" "s"))))]
+	(lo_sum:SI
+	  (match_operand:SI 1 "gpc_reg_operand" "b")
+	  (const
+	    (minus:SI (match_operand:SI 2 "symbol_ref_operand" "s")
+		      (match_operand:SI 3 "symbol_ref_operand" "s")))))]
   "TARGET_ELF && TARGET_SECURE_PLT && DEFAULT_ABI == ABI_V4 && flag_pic"
   "addi %0,%1,%2-%3@l")
 

gcc/testsuite/ChangeLog

+2018-01-10  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR target/83629
+	* gcc.target/powerpc/pr83629.c: New testcase.
+
 2018-01-10  Richard Biener  <rguenther@suse.de>
 
 	PR testsuite/78768

gcc/testsuite/gcc.target/powerpc/pr83629.c

+/* { dg-options "-O2 -fPIC -frename-registers --param=sched-autopref-queue-depth=0 -mcpu=603" } */
+
+extern void bar (void *);
+
+void
+foo (void)
+{
+  bar ("");
+}