Re: [PATCH 1/2] Allow REG_EQUAL for ZERO_EXTRACT

[Kugan]

On 27/07/15 05:38, Andreas Schwab wrote:
> Kugan <kugan.vivekanandara...@linaro.org> writes:
> 
>>      * cse.c (cse_insn): Fix missing check for STRICT_LOW_PART and minor
>>      clean up.
> 
> This breaks 
> 
> gcc.target/m68k/tls-ie-xgot.c scan-assembler jsr __m68k_read_tp
> gcc.target/m68k/tls-ie.c scan-assembler jsr __m68k_read_tp
> gcc.target/m68k/tls-le-xtls.c scan-assembler jsr __m68k_read_tp
> gcc.target/m68k/tls-le.c scan-assembler jsr __m68k_read_tp
> 
> Andreas.
> 

Sorry for the breakage. My patch to add ZERO_EXTRACT unfortunately
restricts the behaviour in one other case. That is, even when REG_EQUAL
note and src are same, we were setting src_eqv to src when it is
STRICT_LOW_PART. Not sure why but restored the old behaviour.

I could reproduce this issue by inspecting the generated asm and made
sure that it is fixed. However I could not run regression for m68k
(Sorry I don’t have access to the set-up).
I bootstrapped and regression tested on x86_64-linux-gnu and
arm-none-linux-gnu with no new regressions.

Thanks,
Kugan


gcc/ChangeLog:

2015-07-27  Kugan Vivekanandarajah  <kug...@linaro.org>

        * cse.c (cse_insn): Restoring old behaviour for src_eqv
         when dest and value in the REG_EQUAL are same and dest
         is STRICT_LOW_PART.

diff --git a/gcc/cse.c b/gcc/cse.c
index 96adf18..17c0954 100644
--- a/gcc/cse.c
+++ b/gcc/cse.c
@@ -4529,12 +4529,13 @@ cse_insn (rtx_insn *insn)
      this case, and if it isn't set, then there will be no equivalence
      for the destination.  */
   if (n_sets == 1 && REG_NOTES (insn) != 0
-      && (tem = find_reg_note (insn, REG_EQUAL, NULL_RTX)) != 0
-      && (! rtx_equal_p (XEXP (tem, 0), SET_SRC (sets[0].rtl))))
+      && (tem = find_reg_note (insn, REG_EQUAL, NULL_RTX)) != 0)
     {
-      if (GET_CODE (SET_DEST (sets[0].rtl)) == STRICT_LOW_PART)
-       src_eqv = copy_rtx (XEXP (tem, 0));
 
+      if (GET_CODE (SET_DEST (sets[0].rtl)) != ZERO_EXTRACT
+         && (! rtx_equal_p (XEXP (tem, 0), SET_SRC (sets[0].rtl))
+             || GET_CODE (SET_DEST (sets[0].rtl)) == STRICT_LOW_PART))
+       src_eqv = copy_rtx (XEXP (tem, 0));
       /* If DEST is of the form ZERO_EXTACT, as in:
         (set (zero_extract:SI (reg:SI 119)
                  (const_int 16 [0x10])