From: Jakub Jelinek <jakub@redhat.com>
Date: Mon, 25 Jun 2018 16:45:10 +0000 (+0200)
Subject: backport: re PR rtl-optimization/82192 (gcc produces incorrect code with -O2 and... 
X-Git-Tag: releases/gcc-6.5.0~254
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2eec8c581c7146616cc23af98ba941e33c75be52;p=thirdparty%2Fgcc.git

backport: re PR rtl-optimization/82192 (gcc produces incorrect code with -O2 and bit-field)

	Backported from mainline
	2017-09-15  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/82192
	* combine.c (make_extraction): Don't look through non-paradoxical
	SUBREGs or TRUNCATE if pos + len is or might be bigger than
	inner's mode.

	* gcc.c-torture/execute/pr82192.c: New test.

From-SVN: r262028
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 62309f352e26..e0da88cd08c7 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -7,6 +7,13 @@
 	* gimplify.c (gimplify_modify_expr): Don't optimize away zero sized
 	lhs from calls if the lhs has addressable type.
 
+	2017-09-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/82192
+	* combine.c (make_extraction): Don't look through non-paradoxical
+	SUBREGs or TRUNCATE if pos + len is or might be bigger than
+	inner's mode.
+
 2018-06-23  Richard Sandiford  <richard.sandiford@linaro.org>
 
 	PR tree-optimization/85989
diff --git a/gcc/combine.c b/gcc/combine.c
index 9b0386c99e77..c38b57dd38e2 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -7336,7 +7336,14 @@ make_extraction (machine_mode mode, rtx inner, HOST_WIDE_INT pos,
   if (pos_rtx && CONST_INT_P (pos_rtx))
     pos = INTVAL (pos_rtx), pos_rtx = 0;
 
-  if (GET_CODE (inner) == SUBREG && subreg_lowpart_p (inner))
+  if (GET_CODE (inner) == SUBREG
+      && subreg_lowpart_p (inner)
+      && (paradoxical_subreg_p (inner)
+	  /* If trying or potentionally trying to extract
+	     bits outside of is_mode, don't look through
+	     non-paradoxical SUBREGs.  See PR82192.  */
+	  || (pos_rtx == NULL_RTX
+	      && pos + len <= GET_MODE_PRECISION (is_mode))))
     {
       /* If going from (subreg:SI (mem:QI ...)) to (mem:QI ...),
 	 consider just the QI as the memory to extract from.
@@ -7362,7 +7369,12 @@ make_extraction (machine_mode mode, rtx inner, HOST_WIDE_INT pos,
       if (new_rtx != 0)
 	return gen_rtx_ASHIFT (mode, new_rtx, XEXP (inner, 1));
     }
-  else if (GET_CODE (inner) == TRUNCATE)
+  else if (GET_CODE (inner) == TRUNCATE
+	   /* If trying or potentionally trying to extract
+	      bits outside of is_mode, don't look through
+	      TRUNCATE.  See PR82192.  */
+	   && pos_rtx == NULL_RTX
+	   && pos + len <= GET_MODE_PRECISION (is_mode))
     inner = XEXP (inner, 0);
 
   inner_mode = GET_MODE (inner);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index b382215ba550..65ee8dae05e1 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -11,6 +11,11 @@
 	PR c++/82159
 	* g++.dg/opt/pr82159.C: New test.
 
+	2017-09-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/82192
+	* gcc.c-torture/execute/pr82192.c: New test.
+
 2018-06-23  Richard Sandiford  <richard.sandiford@linaro.org>
 
 	PR tree-optimization/85989
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr82192.c b/gcc/testsuite/gcc.c-torture/execute/pr82192.c
new file mode 100644
index 000000000000..9e56e203c840
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr82192.c
@@ -0,0 +1,22 @@
+/* PR rtl-optimization/82192 */
+
+unsigned long long int a = 0x95dd3d896f7422e2ULL;
+struct S { unsigned int m : 13; } b;
+
+__attribute__((noinline, noclone)) void
+foo (void)
+{
+  b.m = ((unsigned) a) >> (0x644eee9667723bf7LL
+			   | a & ~0xdee27af8U) - 0x644eee9667763bd8LL;
+}
+
+int
+main ()
+{
+  if (__INT_MAX__ != 0x7fffffffULL)
+    return 0;
+  foo ();
+  if (b.m != 0)
+    __builtin_abort ();
+  return 0;
+}