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PR82816: Widening multiplies of bitfields

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In this PR we tried to create a widening multiply of two 3-bit numbers,
but that isn't a widening multiply at the optab/rtl level, since both
the input and output still have the same mode.

We could trap this either in is_widening_mult_p or (as the patch does)
in the routines that actually ask for an optab.  The latter seemed
more natural since is_widening_mult_p doesn't otherwise care about modes.

2017-11-03  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	PR tree-optimization/82816
	* tree-ssa-math-opts.c (convert_mult_to_widen): Return false
	if the modes of the two types are the same.
	(convert_plusminus_to_widen): Likewise.

gcc/testsuite/
	* gcc.c-torture/compile/pr82816.c: New test.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r254454
This commit is contained in:
Richard Sandiford 2017-11-06 14:47:43 +00:00 committed by Richard Sandiford
parent 962b966886
commit 9134df2c6c
4 changed files with 33 additions and 0 deletions
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9
gcc/ChangeLog
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@ -1,3 +1,12 @@
2017-11-06 Richard Sandiford <richard.sandiford@linaro.org>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>
PR tree-optimization/82816
* tree-ssa-math-opts.c (convert_mult_to_widen): Return false
if the modes of the two types are the same.
(convert_plusminus_to_widen): Likewise.
2017-11-06 Bill Schmidt <wschmidt@linux.vnet.ibm.com>
* config/rs6000/altivec.md (*p9_vadu<mode>3) Rename to

6
gcc/testsuite/ChangeLog
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@ -1,3 +1,9 @@
2017-11-06 Richard Sandiford <richard.sandiford@linaro.org>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>
* gcc.c-torture/compile/pr82816.c: New test.
2017-11-06 Bill Schmidt <wschmidt@linux.vnet.ibm.com>
* gcc.target/powerpc/sad-vectorize-1.c: New file.

12
gcc/testsuite/gcc.c-torture/compile/pr82816.c Normal file
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@ -0,0 +1,12 @@
struct A
{
int b:3;
} d, e;
int c;
void f ()
{
char g = d.b * e.b;
c = g;
}

6
gcc/tree-ssa-math-opts.c
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@ -3259,6 +3259,9 @@ convert_mult_to_widen (gimple *stmt, gimple_stmt_iterator *gsi)
to_mode = SCALAR_INT_TYPE_MODE (type);
from_mode = SCALAR_INT_TYPE_MODE (type1);
if (to_mode == from_mode)
return false;
from_unsigned1 = TYPE_UNSIGNED (type1);
from_unsigned2 = TYPE_UNSIGNED (type2);
@ -3449,6 +3452,9 @@ convert_plusminus_to_widen (gimple_stmt_iterator *gsi, gimple *stmt,
to_mode = SCALAR_TYPE_MODE (type);
from_mode = SCALAR_TYPE_MODE (type1);
if (to_mode == from_mode)
return false;
from_unsigned1 = TYPE_UNSIGNED (type1);
from_unsigned2 = TYPE_UNSIGNED (type2);
optype = type1;