From: khan AT xraylith DOT wisc DOT edu (Mumit Khan)
Subject: egcs-1.1: i386 stdcall function codegen bug
28 Oct 1998 16:20:32 -0800
Message-ID: <Pine.SUN.3.93.981027223545.28077A-200000.cygnus.gnu-win32@modi.xraylith.wisc.edu>
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egcs version : release and mainline
binutils     : 2.9.1 and 980830 snapshots

There seems to be a i386 codegen bug that affects "stdcall" functions
returning anything larger than an integer.

For the following function,

  double __attribute__((stdcall))
  foo_local1 (double f) {
    return f;
  }

The assembly created (using -O2 -fomit-frame-pointer to cut noise), we
get the following. This causes the return value to be garbage unless
I comment out the "fstp" instruction. 

  .globl _foo_local1 AT 8
  _foo_local1 AT 8:
	  fldl 4(%esp)
	  fstp %st(0)		## <<<< offending instruction
	  ret $8

Interestingly, for a "cdecl" function, the fstp instruction is missing
and everything works as expected.

  double 
  foo_local2 (double f) {
    return f;
  }

  .globl _foo_local2
  _foo_local2:
	  fldl 4(%esp)		## <<<< no fstp instruction
	  ret

I'm attaching a trivial, but complete, test program that shows the 
problem.

Regards,
Mumit


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Content-ID: <Pine DOT SUN DOT 3 DOT 93 DOT 981027224052 DOT 28077B AT modi DOT xraylith DOT wisc DOT edu>
Content-Description: bug test case

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