Re: [Patch, tentative, reload] Make push_reload work with more types of subregs?

[Senthil Kumar Selvaraj]

Bernd Schmidt writes:

> On 07/28/2016 09:33 AM, Senthil Kumar Selvaraj wrote:
>>
>>   Is there a reason why only REG and SYMBOL_REFs get valid
>>   subreg_in_class? I tried extending it handle constants and PLUS
>>   expressions, and it fixes PR 71873. It also fixes a another
>>   bug that was a work around for the reload failure (PR 64452) - that
>>   had a plus expression instead of the const.
>>
>>   Reg testing on avr and x86_64 did not show any new failures. Is this
>>   the right way to fix this?
>
> I think it looks quite plausible. Note that testing x86_64 on trunk will 
> not do anything - it is no longer using reload. Could you go back to an 
> older branch (4.7 I think is the last one using reload) and retest 
> x86_64 with that, for better test coverage?

I picked out the commit where you'd added SYMBOL_REF handling (rev
#190252), and patched that with the below code. Bootstrapped and
regtested on x86_64-pc-linux - the results were identical with and 
without the patch. Is this good enough for trunk?

Regards
Senthil

gcc/ChangeLog:

2016-08-08  Senthil Kumar Selvaraj  <senthil_kumar.selva...@atmel.com>

  PR reload/71873
        * reload.c (push_reload): Compute subreg_in_class for
  subregs of constants and plus expressions.

gcc/testsuite/ChangeLog:

2016-08-08  Senthil Kumar Selvaraj  <senthil_kumar.selva...@atmel.com>

        * gcc.target/avr/pr71873.c: New test.


Index: gcc/reload.c
===================================================================
--- gcc/reload.c        (revision 239239)
+++ gcc/reload.c        (working copy)
@@ -1141,7 +1141,9 @@
                                                   SUBREG_BYTE (in),
                                                   GET_MODE (in)),
                              REGNO (SUBREG_REG (in)));
-      else if (GET_CODE (SUBREG_REG (in)) == SYMBOL_REF)
+      else if (GET_CODE (SUBREG_REG (in)) == SYMBOL_REF
+               || CONSTANT_P (SUBREG_REG (in))
+               || GET_CODE (SUBREG_REG (in)) == PLUS)
        subreg_in_class = find_valid_class_1 (inmode,
                                              GET_MODE (SUBREG_REG (in)),
                                              rclass);
Index: gcc/testsuite/gcc.target/avr/pr71873.c
===================================================================
--- gcc/testsuite/gcc.target/avr/pr71873.c      (nonexistent)
+++ gcc/testsuite/gcc.target/avr/pr71873.c      (working copy)
@@ -0,0 +1,30 @@
+/* { dg-do compile } */
+/* { dg-options "-Os -fcaller-saves" } */
+
+#include <stdint.h>
+
+typedef struct {
+  uint8_t x;
+  uint32_t y;
+} A;
+
+A a;
+
+extern int bar(int);
+extern int foo (char *s, ...);
+
+extern uint8_t param;
+extern uint8_t h,m,s,ld,lm;
+extern uint16_t d;
+
+void gps_parse_string(int z)
+{
+  while (bar(z))
+  {
+    switch (param)
+    {
+      case 0: foo("a", &h, &m, &s, &d); break;
+      case 1: foo("d", &ld, &lm, &a.y); break;
+    }
+  }
+}