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regrename: Fix -fcompare-debug issue in check_new_reg_p [PR105041]

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In check_new_reg_p, the nregs of a du chain is computed by obtaining the
MODE of the first element in the chain, and then calling
hard_regno_nregs() with the MODE. But the first element of the chain can
be a DEBUG_INSN whose mode need not be the same as the rest of the
elements in the du chain. This was resulting in fcompare-debug failure
as check_new_reg_p was returning a different result with -g for the same
candidate register. We can instead obtain nregs from the du chain
itself.

2022-06-10  Surya Kumari Jangala  <jskumari@linux.ibm.com>

gcc/
	PR rtl-optimization/105041
	* regrename.cc (check_new_reg_p): Use nregs value from du chain.

gcc/testsuite/
	PR rtl-optimization/105041
	* gcc.target/powerpc/pr105041.c: New test.
This commit is contained in:
Surya Kumari Jangala 2022-06-10 19:52:57 +05:30 • committed by Segher Boessenkool
parent e0e3ce6348
commit 3e16b4359e
2 changed files with 23 additions and 2 deletions
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3
gcc/regrename.cc
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@ -324,8 +324,7 @@ static bool
check_new_reg_p (int reg ATTRIBUTE_UNUSED, int new_reg,
class du_head *this_head, HARD_REG_SET this_unavailable)
{
machine_mode mode = GET_MODE (*this_head->first->loc);
int nregs = hard_regno_nregs (new_reg, mode);
int nregs = this_head->nregs;
int i;
struct du_chain *tmp;

22
gcc/testsuite/gcc.target/powerpc/pr105041.c Normal file
View file

@ -0,0 +1,22 @@
/* { dg-options "-mdejagnu-cpu=power4 -O2 -fcompare-debug -fharden-compares -frename-registers" } */
double m;
int n;
unsigned int
foo (unsigned int x, int y)
{
long long int a = y, b = !a;
int c = 0;
if (b != x)
while ((int) m == a)
{
c = a;
a = 0;
}
n = b = y;
return x + c;
}