Possible CSE quirk involving SUBREG on the i386

[john at feith dot com (John Wehle)]

Compiling:

  unsigned short c;

  int
  func(unsigned short a)
    {
    unsigned short b;
 
    b = a;
    c = b;

    return b;
    }

for the i386 using egcs current with -O -S yields:

_func:
	pushl %ebp
	movl %esp,%ebp
	movl 8(%ebp),%eax
	movl %eax,%edx
	movw %ax,_c
	movzwl %dx,%eax
	leave
	ret

Which is interesting since I expected:

_func:
	pushl %ebp
	movl %esp,%ebp
	movl 8(%ebp),%eax
	movw %ax,_c
	movzwl %ax,%eax
	leave
	ret

The use of %edx seems wasteful.

-- John
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