Hi,
PR93709 mentioned regressions on maxlocval_4.f90 and minlocval_f.f90 which
relates to max of '-inf' and 'nan'. This regression occur on P9 which has
new instruction 'xsmaxcdp/xsmincdp'.
The similar issue also could be find on `a < b ? b : a` which is also
generated as `xsmaxcdp` under -O2 for P9. This instruction `xsmaxcdp`
more like C/C++ semantic (a>b?a:b). A testcase is added for this issue.
The following patch improve code to check -+0 and NaN before 'smax/smin' to
be generated for those cases.
Bootstrap/regtest on powerpc64le pass without regressions.
Is this OK for trunk and backport to GCC 9?
BR.
Jiufu
gcc/
2020-03-05 Jiufu Guo <guoji...@linux.ibm.com>
PR target/93709
* gcc/config/rs6000/rs6000.c (rs6000_emit_p9_fp_minmax): Check
-fno-signed-zeros and -ffinite_math_only for smax/smin.
gcc/testsuite
2020-03-05 Jiufu Guo <guoji...@linux.ibm.com>
PR target/93709
* gcc.target/powerpc/p9-minmax-3.c: New test.
---
gcc/config/rs6000/rs6000.c | 8 +++++++-
gcc/testsuite/gcc.target/powerpc/p9-minmax-3.c | 17 +++++++++++++++++
2 files changed, 24 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.target/powerpc/p9-minmax-3.c
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index f34e1ba70c6..951a6c32884 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -14836,7 +14836,13 @@ rs6000_emit_p9_fp_minmax (rtx dest, rtx op, rtx
true_cond, rtx false_cond)
if (rtx_equal_p (op0, true_cond) && rtx_equal_p (op1, false_cond))
;
- else if (rtx_equal_p (op1, true_cond) && rtx_equal_p (op0, false_cond))
+ /* Only when -fno-signed-zeros and -ffinite_math_only are in effect,
+ `op0 < op1 ? op1 : op0` works like `op1 > op0 ? op1 : op0` which
+ could use smax;
+ `op0 > op1 ? op1 : op0` works like `op1 < op0 ? op1 : op0` which
+ could use smin. */
+ else if (rtx_equal_p (op1, true_cond) && rtx_equal_p (op0, false_cond)
+ && (flag_finite_math_only && !flag_signed_zeros))
max_p = !max_p;
else
diff --git a/gcc/testsuite/gcc.target/powerpc/p9-minmax-3.c
b/gcc/testsuite/gcc.target/powerpc/p9-minmax-3.c
new file mode 100644
index 00000000000..141603e05b4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/p9-minmax-3.c
@@ -0,0 +1,17 @@
+/* { dg-do compile { target { powerpc*-*-* } } } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* { dg-options "-mdejagnu-cpu=power9 -O2 -mpower9-minmax" } */
+/* { dg-final { scan-assembler-not "xsmaxcdp" } } */
+/* { dg-final { scan-assembler-not "xsmincdp" } } */
+
+double
+dbl_max1 (double a, double b)
+{
+ return a < b ? b : a;
+}
+
+double
+dbl_min1 (double a, double b)
+{
+ return a > b ? b : a;
+}
--
2.17.1
