x86 fp fix
Alan Modra
alan@linuxcare.com.au
Mon Mar 27 18:08:00 GMT 2000
On Sat, 25 Mar 2000, Richard Henderson wrote: [some corrections]
Here's a revised patch. I've stopped maligning Unixware too. Robert Lipe
correctly pointed out that the assembly brain damage pre-dates the
Unixware assembler.
I don't have CVS write access, so perhaps someone could check this in for
me.
--
Linuxcare. Support for the Revolution.
gcc/ChangeLog
* config/i386/i386.c (output_387_binary_op): Correct intel
mode assembly output, and add spaces after commas in AT&T
output. Correct Unixware assembler comment. Document input
constraints. Comment fp operations. Reduce profligate buffer
size. Remove extraneous abort. Localize temp var.
(SYSV386_COMPAT): Define. Add !SYSV386_COMPAT code.
(output_fix_trunc): Add spaces after commas in assembly output.
--- gcc/config/i386/i386.c.old Mon Mar 20 23:35:06 2000
+++ gcc/config/i386/i386.c Mon Mar 27 23:26:08 2000
@@ -3434,15 +3434,39 @@ split_di (operands, num, lo_half, hi_hal
There is no guarantee that the operands are the same mode, as they
might be within FLOAT or FLOAT_EXTEND expressions. */
+#ifndef SYSV386_COMPAT
+/* Set to 1 for compatibility with brain-damaged assemblers. No-one
+ wants to fix the assemblers because that causes incompatibility
+ with gcc. No-one wants to fix gcc because that causes
+ incompatibility with assemblers... You can use the option of
+ -DSYSV386_COMPAT=0 if you recompile both gcc and gas this way. */
+#define SYSV386_COMPAT 1
+#endif
+
const char *
output_387_binary_op (insn, operands)
rtx insn;
rtx *operands;
{
- static char buf[100];
- rtx temp;
+ static char buf[30];
const char *p;
+#ifdef ENABLE_CHECKING
+ /* Even if we do not want to check the inputs, this documents input
+ constraints. Which helps in understanding the following code. */
+ if (STACK_REG_P (operands[0])
+ && ((REG_P (operands[1])
+ && REGNO (operands[0]) == REGNO (operands[1])
+ && (STACK_REG_P (operands[2]) || GET_CODE (operands[2]) == MEM))
+ || (REG_P (operands[2])
+ && REGNO (operands[0]) == REGNO (operands[2])
+ && (STACK_REG_P (operands[1]) || GET_CODE (operands[1]) == MEM)))
+ && (STACK_TOP_P (operands[1]) || STACK_TOP_P (operands[2])))
+ ; /* ok */
+ else
+ abort ();
+#endif
+
switch (GET_CODE (operands[3]))
{
case PLUS:
@@ -3489,11 +3513,13 @@ output_387_binary_op (insn, operands)
case PLUS:
if (REG_P (operands[2]) && REGNO (operands[0]) == REGNO (operands[2]))
{
- temp = operands[2];
+ rtx temp = operands[2];
operands[2] = operands[1];
operands[1] = temp;
}
+ /* know operands[0] == operands[1]. */
+
if (GET_CODE (operands[2]) == MEM)
{
p = "%z2\t%2";
@@ -3503,16 +3529,23 @@ output_387_binary_op (insn, operands)
if (find_regno_note (insn, REG_DEAD, REGNO (operands[2])))
{
if (STACK_TOP_P (operands[0]))
- p = "p\t{%0,%2|%2, %0}";
+ /* How is it that we are storing to a dead operand[2]?
+ Well, presumably operands[1] is dead too. We can't
+ store the result to st(0) as st(0) gets popped on this
+ instruction. Instead store to operands[2] (which I
+ think has to be st(1)). st(1) will be popped later.
+ gcc <= 2.8.1 didn't have this check and generated
+ assembly code that the Unixware assembler rejected. */
+ p = "p\t{%0, %2|%2, %0}"; /* st(1) = st(0) op st(1); pop */
else
- p = "p\t{%2,%0|%0, %2}";
+ p = "p\t{%2, %0|%0, %2}"; /* st(r1) = st(r1) op st(0); pop */
break;
}
if (STACK_TOP_P (operands[0]))
- p = "\t{%y2,%0|%0, %y2}";
+ p = "\t{%y2, %0|%0, %y2}"; /* st(0) = st(0) op st(r2) */
else
- p = "\t{%2,%0|%0, %2}";
+ p = "\t{%2, %0|%0, %2}"; /* st(r1) = st(r1) op st(0) */
break;
case MINUS:
@@ -3529,42 +3562,69 @@ output_387_binary_op (insn, operands)
break;
}
- if (! STACK_REG_P (operands[1]) || ! STACK_REG_P (operands[2]))
- abort ();
-
- /* Note that the Unixware assembler, and the AT&T assembler before
- that, are confusingly not reversed from Intel syntax in this
- area. */
if (find_regno_note (insn, REG_DEAD, REGNO (operands[2])))
{
+#if SYSV386_COMPAT
+ /* The SystemV/386 SVR3.2 assembler, and probably all AT&T
+ derived assemblers, confusingly reverse the direction of
+ the operation for fsub{r} and fdiv{r} when the
+ destination register is not st(0). The Intel assembler
+ doesn't have this brain damage. Read !SYSV386_COMPAT to
+ figure out what the hardware really does. */
+ if (STACK_TOP_P (operands[0]))
+ p = "{p\t%0, %2|rp\t%2, %0}";
+ else
+ p = "{rp\t%2, %0|p\t%0, %2}";
+#else
if (STACK_TOP_P (operands[0]))
- p = "p\t%0,%2";
+ /* As above for fmul/fadd, we can't store to st(0). */
+ p = "rp\t{%0, %2|%2, %0}"; /* st(1) = st(0) op st(1); pop */
else
- p = "rp\t%2,%0";
+ p = "p\t{%2, %0|%0, %2}"; /* st(r1) = st(r1) op st(0); pop */
+#endif
break;
}
if (find_regno_note (insn, REG_DEAD, REGNO (operands[1])))
{
+#if SYSV386_COMPAT
+ if (STACK_TOP_P (operands[0]))
+ p = "{rp\t%0, %1|p\t%1, %0}";
+ else
+ p = "{p\t%1, %0|rp\t%0, %1}";
+#else
if (STACK_TOP_P (operands[0]))
- p = "rp\t%0,%1";
+ p = "p\t{%0, %1|%1, %0}"; /* st(1) = st(1) op st(0); pop */
else
- p = "p\t%1,%0";
+ p = "rp\t{%1, %0|%0, %1}"; /* st(r2) = st(0) op st(r2); pop */
+#endif
break;
}
if (STACK_TOP_P (operands[0]))
{
if (STACK_TOP_P (operands[1]))
- p = "\t%y2,%0";
+ p = "\t{%y2, %0|%0, %y2}"; /* st(0) = st(0) op st(r2) */
else
- p = "r\t%y1,%0";
+ p = "r\t{%y1, %0|%0, %y1}"; /* st(0) = st(r1) op st(0) */
break;
}
else if (STACK_TOP_P (operands[1]))
- p = "\t%1,%0";
+ {
+#if SYSV386_COMPAT
+ p = "{\t%1, %0|r\t%0, %1}";
+#else
+ p = "r\t{%1, %0|%0, %1}"; /* st(r2) = st(0) op st(r2) */
+#endif
+ }
else
- p = "r\t%2,%0";
+ {
+#if SYSV386_COMPAT
+ p = "{r\t%2, %0|\t%0, %2}";
+#else
+ p = "\t{%2, %0|%0, %2}"; /* st(r1) = st(r1) op st(0) */
+#endif
+ }
break;
default:
@@ -3628,7 +3688,7 @@ output_fix_trunc (insn, operands)
output_asm_insn ("mov{l}\t{%3, %1|%1, %3}", xops);
}
else
- output_asm_insn ("mov{l}\t{%3,%0|%0, %3}", operands);
+ output_asm_insn ("mov{l}\t{%3, %0|%0, %3}", operands);
}
return "";
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