tree-optimization/104511 - avoid FP to DFP conversion for VEC_PACK_TRUNC

This avoids forwprop from matching DFP <-> FP vector conversions
using VEC_[UN]PACK{_TRUNC,_LO,_HI}.  Maybe DFP vectors shouldn't be
a thing, but they appearantly are.  Re-using CONVERT/NOP_EXPR for
DFP <-> FP conversions was probably a mistake.

2022-02-14  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/104511
	* tree-ssa-forwprop.cc (simplify_vector_constructor): Avoid
	touching DFP <-> FP conversions.

	* gcc.dg/pr104511.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/pr104511.c b/gcc/testsuite/gcc.dg/pr104511.c
new file mode 100644 (file)
index 0000000..ad5430c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr104511.c
@@ -0,0 +1,16 @@
+/* { dg-do compile { target dfp } } */
+/* { dg-options "-O -Wno-psabi" } */
+
+typedef _Float64 __attribute__((__vector_size__ (32))) F;
+typedef _Decimal32 __attribute__((__vector_size__ (16))) D;
+
+extern void bar (void);
+
+D g;
+void
+foo (F f)
+{
+  D d = __builtin_convertvector (f, D);
+  bar ();
+  g = d;
+}

diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
index 709bde6..484491f 100644 (file)
--- a/gcc/tree-ssa-forwprop.cc
+++ b/gcc/tree-ssa-forwprop.cc
@@ -2824,6 +2824,15 @@ simplify_vector_constructor (gimple_stmt_iterator *gsi)
                         ? VEC_UNPACK_FLOAT_HI_EXPR
                         : VEC_UNPACK_HI_EXPR);
 
+         /* Conversions between DFP and FP have no special tree code
+            but we cannot handle those since all relevant vector conversion
+            optabs only have a single mode.  */
+         if (CONVERT_EXPR_CODE_P (conv_code)
+             && FLOAT_TYPE_P (TREE_TYPE (type))
+             && (DECIMAL_FLOAT_TYPE_P (TREE_TYPE (type))
+                 != DECIMAL_FLOAT_TYPE_P (TREE_TYPE (conv_src_type))))
+           return false;
+
          if (CONVERT_EXPR_CODE_P (conv_code)
              && (2 * TYPE_PRECISION (TREE_TYPE (TREE_TYPE (orig[0])))
                  == TYPE_PRECISION (TREE_TYPE (type)))