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authorAleksandar Markovic <aleksandar.markovic@imgtec.com>2017-07-27 18:08:56 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-09-27 14:39:20 +0200
commitd56a9caf6d836d22868404818a652fc85744774a (patch)
tree5000f957d53f28a2e05689df001d65515e22685d /arch/mips
parent8981bcaf9a2da24baeb76cd39d43cf2bc2569509 (diff)
MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Fix some cases of zero inputs
commit 7cf64ce4d37f1b4f44365fcf77f565d523819dcd upstream. Fix the cases of <MADDF|MSUBF>.<D|S> when any of two multiplicands is +0 or -0, and the third input is also +0 or -0. Depending on the signs of inputs, certain special cases must be handled. A relevant example: MADDF.S fd,fs,ft: If fs contains +0.0, ft contains -0.0, and fd contains 0.0, fd is going to contain +0.0 (without this patch, it used to contain -0.0). Fixes: e24c3bec3e8e ("MIPS: math-emu: Add support for the MIPS R6 MADDF FPU instruction") Fixes: 83d43305a1df ("MIPS: math-emu: Add support for the MIPS R6 MSUBF FPU instruction") Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com> Signed-off-by: Goran Ferenc <goran.ferenc@imgtec.com> Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com> Reviewed-by: James Hogan <james.hogan@imgtec.com> Cc: Bo Hu <bohu@google.com> Cc: Douglas Leung <douglas.leung@imgtec.com> Cc: Jin Qian <jinqian@google.com> Cc: Paul Burton <paul.burton@imgtec.com> Cc: Petar Jovanovic <petar.jovanovic@imgtec.com> Cc: Raghu Gandham <raghu.gandham@imgtec.com> Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/16888/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/mips')
-rw-r--r--arch/mips/math-emu/dp_maddf.c18
-rw-r--r--arch/mips/math-emu/sp_maddf.c18
2 files changed, 34 insertions, 2 deletions
diff --git a/arch/mips/math-emu/dp_maddf.c b/arch/mips/math-emu/dp_maddf.c
index 557a0a118827..c38fe1bde875 100644
--- a/arch/mips/math-emu/dp_maddf.c
+++ b/arch/mips/math-emu/dp_maddf.c
@@ -113,7 +113,23 @@ static union ieee754dp _dp_maddf(union ieee754dp z, union ieee754dp x,
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
if (zc == IEEE754_CLASS_INF)
return ieee754dp_inf(zs);
- /* Multiplication is 0 so just return z */
+ if (zc == IEEE754_CLASS_ZERO) {
+ /* Handle cases +0 + (-0) and similar ones. */
+ if ((!(flags & maddf_negate_product)
+ && (zs == (xs ^ ys))) ||
+ ((flags & maddf_negate_product)
+ && (zs != (xs ^ ys))))
+ /*
+ * Cases of addition of zeros of equal signs
+ * or subtraction of zeroes of opposite signs.
+ * The sign of the resulting zero is in any
+ * such case determined only by the sign of z.
+ */
+ return z;
+
+ return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
+ }
+ /* x*y is here 0, and z is not 0, so just return z */
return z;
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
diff --git a/arch/mips/math-emu/sp_maddf.c b/arch/mips/math-emu/sp_maddf.c
index 0d8d25f4b737..4241ec19df12 100644
--- a/arch/mips/math-emu/sp_maddf.c
+++ b/arch/mips/math-emu/sp_maddf.c
@@ -114,7 +114,23 @@ static union ieee754sp _sp_maddf(union ieee754sp z, union ieee754sp x,
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
if (zc == IEEE754_CLASS_INF)
return ieee754sp_inf(zs);
- /* Multiplication is 0 so just return z */
+ if (zc == IEEE754_CLASS_ZERO) {
+ /* Handle cases +0 + (-0) and similar ones. */
+ if ((!(flags & maddf_negate_product)
+ && (zs == (xs ^ ys))) ||
+ ((flags & maddf_negate_product)
+ && (zs != (xs ^ ys))))
+ /*
+ * Cases of addition of zeros of equal signs
+ * or subtraction of zeroes of opposite signs.
+ * The sign of the resulting zero is in any
+ * such case determined only by the sign of z.
+ */
+ return z;
+
+ return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
+ }
+ /* x*y is here 0, and z is not 0, so just return z */
return z;
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):