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powerpc: Restrict xssqrtqp operands to Vector Registers (bug 21941)

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POWER ISA 3.0 introduces the xssqrtqp instructions, which expects
operands to be in Vector Registers (Altivec/VMX), even though this
instruction belongs to the Vector-Scalar Instruction Set.

In GCC's Extended Assembly for POWER, the 'wq' register constraint is
provided for use with IEEE 754 128-bit floating-point values.  However,
this constraint does not limit the register allocation to Vector
Registers (Altivec/VMX) and could assign a Vector-Scalar Register (VSX)
to the operands of the instruction.

This patch changes the register constraint used in sqrtf128 from 'wq' to
'v', in order to request a Vector Register (Altivec/VMX) for use with
the xssqrtqp instruction.

Tested for powerpc64le and --with-cpu=power9.

	[BZ #21941]
	* sysdeps/powerpc/fpu/math_private.h (__ieee754_sqrtf128): Since
	xssqrtqp requires operands to be in Vector Registers
	(Altivec/VMX), replace the register constraint 'wq' with 'v'.
	* sysdeps/powerpc/powerpc64le/power9/fpu/e_sqrtf128.c
	(__ieee754_sqrtf128): Likewise.
This commit is contained in:
Gabriel F. T. Gomes 2017-08-07 09:14:14 -03:00
parent 922369032c
commit 4d98ace9de
3 changed files with 11 additions and 2 deletions
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9
ChangeLog
View File

@ -1,3 +1,12 @@
2017-08-10 Gabriel F. T. Gomes <gftg@linux.vnet.ibm.com>
[BZ #21941]
* sysdeps/powerpc/fpu/math_private.h (__ieee754_sqrtf128): Since
xssqrtqp requires operands to be in Vector Registers
(Altivec/VMX), replace the register constraint 'wq' with 'v'.
* sysdeps/powerpc/powerpc64le/power9/fpu/e_sqrtf128.c
(__ieee754_sqrtf128): Likewise.
2017-08-10 Wilco Dijkstra <wdijkstr@arm.com>
* sysdeps/aarch64/memcmp.S (memcmp):

2
sysdeps/powerpc/fpu/math_private.h
View File

@ -30,7 +30,7 @@ extern __always_inline _Float128
__ieee754_sqrtf128 (_Float128 __x)
{
_Float128 __z;
asm ("xssqrtqp %0,%1" : "=wq" (__z) : "wq" (__x));
asm ("xssqrtqp %0,%1" : "=v" (__z) : "v" (__x));
return __z;
}
#endif

2
sysdeps/powerpc/powerpc64le/power9/fpu/e_sqrtf128.c
View File

@ -30,7 +30,7 @@ __float128
__ieee754_sqrtf128 (__float128 a)
{
__float128 z;
asm ("xssqrtqp %0,%1" : "=wq" (z) : "wq" (a));
asm ("xssqrtqp %0,%1" : "=v" (z) : "v" (a));
return z;
}
strong_alias (__ieee754_sqrtf128, __sqrtf128_finite)