From: Richard Biener <rguenther@suse.de>
Date: Mon, 14 Feb 2022 09:09:10 +0000 (+0100)
Subject: tree-optimization/104511 - avoid FP to DFP conversion for VEC_PACK_TRUNC
X-Git-Tag: basepoints/gcc-13~1089
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f320197c8b495324dc6997a99d53e7f45ecf5840;p=thirdparty%2Fgcc.git

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
index 000000000000..ad5430c67c84
--- /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 709bde6defa7..484491fa1c50 100644
--- 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)))