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(alpha_emit_set_const): Don't output SImode sequences that rely on invisible overflow. 

(alpha_emit_set_const): Don't output SImode sequences that rely on
invisible overflow.  Sign extend new when SImode.  Don't recur if new
== c.  Don't allow shift outside mode.  Make logical right shift be
unsigned.

From-SVN: r10589
This commit is contained in:
Richard Kenner 1995-11-26 12:08:18 -05:00
parent 63a014a083
commit 57cfde96bb
1 changed files with 23 additions and 7 deletions
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30
gcc/config/alpha/alpha.c
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@ -713,7 +713,12 @@ alpha_emit_set_const (target, mode, c, n)
if (c == low || (low == 0 && extra == 0))
return copy_to_suggested_reg (GEN_INT (c), target, mode);
else if (n >= 2 + (extra != 0))
else if (n >= 2 + (extra != 0)
/* We can't do this when SImode if HIGH required adjustment.
This is because the code relies on an implicit overflow
which is invisible to the RTL. We can thus get incorrect
code if the two ldah instructions are combined. */
&& ! (mode == SImode && extra != 0))
{
temp = copy_to_suggested_reg (GEN_INT (low), subtarget, mode);
@ -744,7 +749,14 @@ alpha_emit_set_const (target, mode, c, n)
if ((new & ((HOST_WIDE_INT) 0xff << i)) == 0)
new |= (HOST_WIDE_INT) 0xff << i;
if ((temp = alpha_emit_set_const (subtarget, mode, new, n - 1)) != 0)
/* We are only called for SImode and DImode. If this is SImode, ensure that
we are sign extended to a full word. */
if (mode == SImode)
new = (new & 0xffffffff) - 2 * (new & 0x80000000);
if (new != c
&& (temp = alpha_emit_set_const (subtarget, mode, new, n - 1)) != 0)
return expand_binop (mode, and_optab, temp, GEN_INT (c | ~ new),
target, 0, OPTAB_WIDEN);
#endif
@ -781,9 +793,11 @@ alpha_emit_set_const (target, mode, c, n)
target, 0, OPTAB_WIDEN);
/* Now try high-order zero bits. Here we try the shifted-in bits as
all zero and all ones. */
all zero and all ones. Be careful to avoid shifting outside the
mode and to avoid shifting outside the host wide int size. */
if ((bits = HOST_BITS_PER_WIDE_INT - floor_log2 (c) - 1) > 0)
if ((bits = (MIN (HOST_BITS_PER_WIDE_INT, GET_MODE_SIZE (mode) * 8)
- floor_log2 (c) - 1)) > 0)
for (; bits > 0; bits--)
if ((temp = alpha_emit_set_const (subtarget, mode,
c << bits, i)) != 0
@ -793,12 +807,14 @@ alpha_emit_set_const (target, mode, c, n)
i)))
!= 0))
return expand_binop (mode, lshr_optab, temp, GEN_INT (bits),
target, 0, OPTAB_WIDEN);
target, 1, OPTAB_WIDEN);
/* Now try high-order 1 bits. We get that with a sign-extension.
But one bit isn't enough here. */
But one bit isn't enough here. Be careful to avoid shifting outside
the mode and to avoid shifting outside the host wide int size. */
if ((bits = HOST_BITS_PER_WIDE_INT - floor_log2 (~ c) - 2) > 0)
if ((bits = (MIN (HOST_BITS_PER_WIDE_INT, GET_MODE_SIZE (mode) * 8)
- floor_log2 (~ c) - 2)) > 0)
for (; bits > 0; bits--)
if ((temp = alpha_emit_set_const (subtarget, mode,
c << bits, i)) != 0