From: Kewen Lin <linkw@linux.ibm.com>
Date: Mon, 12 Jun 2023 06:07:52 +0000 (-0500)
Subject: rs6000: Don't use TFmode for 128 bits fp constant in toc [PR110011]
X-Git-Tag: basepoints/gcc-15~8436
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=388809f2afde874180da0669c669e241037eeba0;p=thirdparty%2Fgcc.git

rs6000: Don't use TFmode for 128 bits fp constant in toc [PR110011]

As PR110011 shows, when encoding 128 bits fp constant into
toc, we adopts REAL_VALUE_TO_TARGET_LONG_DOUBLE which is
to find the first float mode with LONG_DOUBLE_TYPE_SIZE
bits of precision, it would be TFmode here.  But the 128
bits fp constant can be with mode IFmode or KFmode, which
doesn't necessarily have the same underlying float format
as the one of TFmode, like this PR exposes, with option
-mabi=ibmlongdouble TFmode has ibm_extended_format while
KFmode has ieee_quad_format, mixing up the formats (the
encoding/decoding ways) would cause unexpected results.

This patch is to make it use constant's own mode instead
of TFmode for real_to_target call.

	PR target/110011

gcc/ChangeLog:

	* config/rs6000/rs6000.cc (output_toc): Use the mode of the 128-bit
	floating constant itself for real_to_target call.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr110011.c: New test.
---

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index d197c3f3289a..ea68ca6faef0 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -17322,7 +17322,7 @@ output_toc (FILE *file, rtx x, int labelno, machine_mode mode)
       if (DECIMAL_FLOAT_MODE_P (GET_MODE (x)))
 	REAL_VALUE_TO_TARGET_DECIMAL128 (*CONST_DOUBLE_REAL_VALUE (x), k);
       else
-	REAL_VALUE_TO_TARGET_LONG_DOUBLE (*CONST_DOUBLE_REAL_VALUE (x), k);
+	real_to_target (k, CONST_DOUBLE_REAL_VALUE (x), GET_MODE (x));
 
       if (TARGET_64BIT)
 	{
diff --git a/gcc/testsuite/gcc.target/powerpc/pr110011.c b/gcc/testsuite/gcc.target/powerpc/pr110011.c
new file mode 100644
index 000000000000..5b04d3e298a8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr110011.c
@@ -0,0 +1,42 @@
+/* { dg-do run } */
+/* { dg-require-effective-target float128_runtime } */
+/* Force long double to be with IBM format here, to verify
+   _Float128 constant still uses its own format (IEEE) for
+   encoding rather than IBM format.  */
+/* { dg-options "-mfp-in-toc -mabi=ibmlongdouble" } */
+/* { dg-add-options float128 } */
+
+#define MPFR_FLOAT128_MAX 0x1.ffffffffffffffffffffffffffffp+16383f128
+
+__attribute__ ((noipa))
+_Float128 f128_max ()
+{
+  return MPFR_FLOAT128_MAX;
+}
+
+typedef union
+{
+  int w[4];
+  _Float128 f128;
+} U;
+
+int main ()
+{
+
+  U umax;
+  umax.f128 = f128_max ();
+  /* ieee float128 max:
+     7ffeffff ffffffff ffffffff ffffffff.  */
+  if (umax.w[1] != 0xffffffff || umax.w[2] != 0xffffffff)
+    __builtin_abort ();
+#ifdef __LITTLE_ENDIAN__
+  if (umax.w[0] != 0xffffffff || umax.w[3] != 0x7ffeffff)
+    __builtin_abort ();
+#else
+  if (umax.w[3] != 0xffffffff || umax.w[0] != 0x7ffeffff)
+    __builtin_abort ();
+#endif
+
+  return 0;
+}
+