arm: Fix multiple inheritance thunks for thumb-1 with -mpure-code

When -mpure-code is used, we cannot load delta from code memory (like
we do without -mpure-code).

This patch builds the value of mi_delta into r3 with a series of
movs/adds/lsls.

We also do some cleanup by not emitting the function address and delta
via .word directives at the end of the thunk since we don't use them
with -mpure-code.

No need for new testcases, this bug was already identified by:
g++.dg/ipa/pr46287-3.C
g++.dg/ipa/pr46984.C
g++.dg/opt/thunk1.C
g++.dg/torture/pr46287.C
g++.dg/torture/pr45699.C

2020-11-02  Christophe Lyon  <christophe.lyon@linaro.org>

	gcc/
	* config/arm/arm.c (arm_thumb1_mi_thunk): Build mi_delta in r3 and
	do not emit function address and delta when -mpure-code is used.

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index bfc1249f94189c02097d1eaa047cbcae095e7c00..5612d1e7e180589a04214c4b18fed33d50ba76e8 100644 (file)
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -28528,9 +28528,19 @@ arm_thumb1_mi_thunk (FILE *file, tree, HOST_WIDE_INT delta,
     {
       if (mi_delta > 255)
        {
-         fputs ("\tldr\tr3, ", file);
-         assemble_name (file, label);
-         fputs ("+4\n", file);
+         /* With -mpure-code, we cannot load MI_DELTA from the
+            constant pool: we build it explicitly.  */
+         if (target_pure_code)
+           {
+             thumb1_const_print r3 (file, 3);
+             thumb1_gen_const_int_1 (r3, mi_delta);
+           }
+         else
+           {
+             fputs ("\tldr\tr3, ", file);
+             assemble_name (file, label);
+             fputs ("+4\n", file);
+           }
          asm_fprintf (file, "\t%ss\t%r, %r, r3\n",
                       mi_op, this_regno, this_regno);
        }
@@ -28566,30 +28576,37 @@ arm_thumb1_mi_thunk (FILE *file, tree, HOST_WIDE_INT delta,
        fputs ("\tpop\t{r3}\n", file);
 
       fprintf (file, "\tbx\tr12\n");
-      ASM_OUTPUT_ALIGN (file, 2);
-      assemble_name (file, label);
-      fputs (":\n", file);
-      if (flag_pic)
+
+      /* With -mpure-code, we don't need to emit literals for the
+        function address and delta since we emitted code to build
+        them.  */
+      if (!target_pure_code)
        {
-         /* Output ".word .LTHUNKn-[3,7]-.LTHUNKPCn".  */
-         rtx tem = XEXP (DECL_RTL (function), 0);
-         /* For TARGET_THUMB1_ONLY the thunk is in Thumb mode, so the PC
-            pipeline offset is four rather than eight.  Adjust the offset
-            accordingly.  */
-         tem = plus_constant (GET_MODE (tem), tem,
-                              TARGET_THUMB1_ONLY ? -3 : -7);
-         tem = gen_rtx_MINUS (GET_MODE (tem),
-                              tem,
-                              gen_rtx_SYMBOL_REF (Pmode,
-                                                  ggc_strdup (labelpc)));
-         assemble_integer (tem, 4, BITS_PER_WORD, 1);
-       }
-      else
-       /* Output ".word .LTHUNKn".  */
-       assemble_integer (XEXP (DECL_RTL (function), 0), 4, BITS_PER_WORD, 1);
+         ASM_OUTPUT_ALIGN (file, 2);
+         assemble_name (file, label);
+         fputs (":\n", file);
+         if (flag_pic)
+           {
+             /* Output ".word .LTHUNKn-[3,7]-.LTHUNKPCn".  */
+             rtx tem = XEXP (DECL_RTL (function), 0);
+             /* For TARGET_THUMB1_ONLY the thunk is in Thumb mode, so the PC
+                pipeline offset is four rather than eight.  Adjust the offset
+                accordingly.  */
+             tem = plus_constant (GET_MODE (tem), tem,
+                                  TARGET_THUMB1_ONLY ? -3 : -7);
+             tem = gen_rtx_MINUS (GET_MODE (tem),
+                                  tem,
+                                  gen_rtx_SYMBOL_REF (Pmode,
+                                                      ggc_strdup (labelpc)));
+             assemble_integer (tem, 4, BITS_PER_WORD, 1);
+           }
+         else
+           /* Output ".word .LTHUNKn".  */
+           assemble_integer (XEXP (DECL_RTL (function), 0), 4, BITS_PER_WORD, 1);
 
-      if (TARGET_THUMB1_ONLY && mi_delta > 255)
-       assemble_integer (GEN_INT(mi_delta), 4, BITS_PER_WORD, 1);
+         if (TARGET_THUMB1_ONLY && mi_delta > 255)
+           assemble_integer (GEN_INT (mi_delta), 4, BITS_PER_WORD, 1);
+       }
     }
   else
     {