Fix uninitialised use in mips_split_move

Fix uninitialised use in mips_split_move

[Richard Sandiford]

While testing the fix for PR91068, I hit an rtl checking failure
while building newlib.  mips_split_move was decomposing an address that
happened to be symbolic and then tried to access the REGNO of the base
register field, which wasn't initialised but which by chance pointed to
valid memory.

Tested on mipsisa64-elf.  OK to install?

Richard


2019-07-05  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/mips/mips.c (mips_split_move): Zero-initialize addr
	and check whether addr.reg is nonnull before using it.

Index: gcc/config/mips/mips.c
===================================================================
--- gcc/config/mips/mips.c	2019-07-01 09:37:07.300523814 +0100
+++ gcc/config/mips/mips.c	2019-07-05 09:46:46.407526855 +0100
@@ -4849,7 +4849,7 @@ mips_split_move (rtx dest, rtx src, enum
      can forward SRC for DEST.  This is most useful if the next insn is a
      simple store.   */
   rtx_insn *insn = (rtx_insn *)insn_;
-  struct mips_address_info addr;
+  struct mips_address_info addr = {};
   if (insn)
     {
       rtx_insn *next = next_nonnote_nondebug_insn_bb (insn);
@@ -4862,7 +4862,7 @@ mips_split_move (rtx dest, rtx src, enum
 		{
 		  rtx tmp = XEXP (src, 0);
 		  mips_classify_address (&addr, tmp, GET_MODE (tmp), true);
-		  if (REGNO (addr.reg) != REGNO (dest))
+		  if (addr.reg && REGNO (addr.reg) != REGNO (dest))
 		    validate_change (next, &SET_SRC (set), src, false);
 		}
 	      else

Re: Fix uninitialised use in mips_split_move

[Jeff Law]

On 7/5/19 2:48 AM, Richard Sandiford wrote:
> While testing the fix for PR91068, I hit an rtl checking failure
> while building newlib.  mips_split_move was decomposing an address that
> happened to be symbolic and then tried to access the REGNO of the base
> register field, which wasn't initialised but which by chance pointed to
> valid memory.
> 
> Tested on mipsisa64-elf.  OK to install?
> 
> Richard
> 
> 
> 2019-07-05  Richard Sandiford  <richard.sandiford@arm.com>
> 
> gcc/
> 	* config/mips/mips.c (mips_split_move): Zero-initialize addr
> 	and check whether addr.reg is nonnull before using it.
OK
jeff