[PATCH, GCC/ARM] Fix clear_operation_p uninitialised variable

[Mihail Ionescu]

Hi,


This patch fixes the uninitialised 'last_regno' variable introduced in:
https://gcc.gnu.org/ml/gcc-patches/2019-12/msg01299.html
and makes the clear_operation_p code more readable.

*** gcc/ChangeLog ***

2020-01-20  Mihail-Calin Ionescu  <mihail.ione...@arm.com>

        * gcc/config/arm/arm.c (clear_operation_p):
        Initialise last_regno, skip first iteration
        based on the first_set value and use ints instead
        of the unnecessary HOST_WIDE_INTs.



Is it ok for trunk?


Regards,
Mihail


###############     Attachment also inlined for ease of reply    ###############


diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 
4bfceb973c47f64b2705c1ab47cc61c9f78508a9..52e1db22ac18bc281ca3deb8cf950eb3438c7e52
 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -13751,13 +13751,14 @@ ldm_stm_operation_p (rtx op, bool load, machine_mode 
mode,
 bool
 clear_operation_p (rtx op, bool vfp)
 {
-  unsigned regno, last_regno;
+  unsigned regno;
+  unsigned last_regno = INVALID_REGNUM;
   rtx elt, reg, zero;
-  HOST_WIDE_INT count = XVECLEN (op, 0);
-  HOST_WIDE_INT i, first_set = vfp ? 1 : 0;
+  int count = XVECLEN (op, 0);
+  int first_set = vfp ? 1 : 0;
   machine_mode expected_mode = vfp ? E_SFmode : E_SImode;
 
-  for (i = first_set; i < count; i++)
+  for (int i = first_set; i < count; i++)
     {
       elt = XVECEXP (op, 0, i);
 
@@ -13789,14 +13790,14 @@ clear_operation_p (rtx op, bool vfp)
 
       if (vfp)
        {
-         if (i != 1 && regno != last_regno + 1)
+         if (i != first_set && regno != last_regno + 1)
            return false;
        }
       else
        {
          if (regno == SP_REGNUM || regno == PC_REGNUM)
            return false;
-         if (i != 0 && regno <= last_regno)
+         if (i != first_set && regno <= last_regno)
            return false;
        }
 


diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 
4bfceb973c47f64b2705c1ab47cc61c9f78508a9..52e1db22ac18bc281ca3deb8cf950eb3438c7e52
 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -13751,13 +13751,14 @@ ldm_stm_operation_p (rtx op, bool load, machine_mode 
mode,
 bool
 clear_operation_p (rtx op, bool vfp)
 {
-  unsigned regno, last_regno;
+  unsigned regno;
+  unsigned last_regno = INVALID_REGNUM;
   rtx elt, reg, zero;
-  HOST_WIDE_INT count = XVECLEN (op, 0);
-  HOST_WIDE_INT i, first_set = vfp ? 1 : 0;
+  int count = XVECLEN (op, 0);
+  int first_set = vfp ? 1 : 0;
   machine_mode expected_mode = vfp ? E_SFmode : E_SImode;
 
-  for (i = first_set; i < count; i++)
+  for (int i = first_set; i < count; i++)
     {
       elt = XVECEXP (op, 0, i);
 
@@ -13789,14 +13790,14 @@ clear_operation_p (rtx op, bool vfp)
 
       if (vfp)
        {
-         if (i != 1 && regno != last_regno + 1)
+         if (i != first_set && regno != last_regno + 1)
            return false;
        }
       else
        {
          if (regno == SP_REGNUM || regno == PC_REGNUM)
            return false;
-         if (i != 0 && regno <= last_regno)
+         if (i != first_set && regno <= last_regno)
            return false;
        }