From: Jakub Jelinek <jakub@redhat.com>
Date: Fri, 30 Aug 2019 12:19:33 +0000 (+0200)
Subject: backport: re PR rtl-optimization/89679 (wrong code with -Og -frerun-cse-after-loop... 
X-Git-Tag: releases/gcc-7.5.0~231
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fa03ad48fe352340b987a80d72576c504c462af7;p=thirdparty%2Fgcc.git

backport: re PR rtl-optimization/89679 (wrong code with -Og -frerun-cse-after-loop -fno-tree-fre)

	Backported from mainline
	2019-03-14  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/89679
	* expmed.c (expand_mult_const): Don't add a REG_EQUAL note if it
	would contain a paradoxical SUBREG.

	* gcc.dg/pr89679.c: New test.

From-SVN: r275132
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1be99eebeef2..37e1a9fe8efc 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -3,6 +3,10 @@
 	Backported from mainline
 	2019-03-14  Jakub Jelinek  <jakub@redhat.com>
 
+	PR rtl-optimization/89679
+	* expmed.c (expand_mult_const): Don't add a REG_EQUAL note if it
+	would contain a paradoxical SUBREG.
+
 	PR tree-optimization/89703
 	* tree-ssa-strlen.c (valid_builtin_call): Punt if stmt call types
 	aren't compatible also with builtin_decl_explicit.  Check pure
diff --git a/gcc/expmed.c b/gcc/expmed.c
index b9f12576b0cf..06a06d1a0cc0 100644
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -3179,11 +3179,19 @@ expand_mult_const (machine_mode mode, rtx op0, HOST_WIDE_INT val,
 	      tem = gen_lowpart (nmode, op0);
 	    }
 
-          insn = get_last_insn ();
-          set_dst_reg_note (insn, REG_EQUAL,
-			    gen_rtx_MULT (nmode, tem,
-					  gen_int_mode (val_so_far, nmode)),
-			    accum_inner);
+	  /* Don't add a REG_EQUAL note if tem is a paradoxical SUBREG.
+	     In that case, only the low bits of accum would be guaranteed to
+	     be equal to the content of the REG_EQUAL note, the upper bits
+	     can be anything.  */
+	  if (!paradoxical_subreg_p (tem))
+	    {
+	      insn = get_last_insn ();
+	      set_dst_reg_note (insn, REG_EQUAL,
+				gen_rtx_MULT (nmode, tem,
+					      gen_int_mode (val_so_far,
+							    nmode)),
+				accum_inner);
+	    }
 	}
     }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e5525de68184..d9fdc68c19ef 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -3,6 +3,9 @@
 	Backported from mainline
 	2019-03-14  Jakub Jelinek  <jakub@redhat.com>
 
+	PR rtl-optimization/89679
+	* gcc.dg/pr89679.c: New test.
+
 	PR tree-optimization/89703
 	* gcc.c-torture/compile/pr89703-1.c: New test.
 	* gcc.c-torture/compile/pr89703-2.c: New test.
diff --git a/gcc/testsuite/gcc.dg/pr89679.c b/gcc/testsuite/gcc.dg/pr89679.c
new file mode 100644
index 000000000000..0d6e2d2c8716
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr89679.c
@@ -0,0 +1,26 @@
+/* PR rtl-optimization/89679 */
+/* { dg-do run } */
+/* { dg-options "-Og -frerun-cse-after-loop -fno-tree-fre" } */
+
+unsigned short g;
+
+void
+foo (unsigned long long x)
+{
+  if (x != 0xffff)
+    __builtin_abort ();
+}
+
+int
+main ()
+{
+#if __SIZEOF_SHORT__ == 2 && __SIZEOF_INT__ == 4 && __CHAR_BIT__ == 8
+  unsigned short d = 0;
+  unsigned long long x, c = ~0;
+  c = c >> d;
+  __builtin_memset (&d, c, 2);
+  x = d + g;
+  foo (x);
+#endif
+  return 0;
+}