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

	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: r252824

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 509742ac0cca09e3564a93f2d2a62d4799434205..8c9988fccfb1c35b9dfb9eb702ada3eab3ed480f 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+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.
+
 2017-09-15  Richard Sandiford  <richard.sandiford@linaro.org>
            Alan Hayward  <alan.hayward@arm.com>
            David Sherwood  <david.sherwood@arm.com>

diff --git a/gcc/combine.c b/gcc/combine.c
index ccfee26333b400b0873f255ff67cb7bdbb301b35..e502fa147267d071adc0e47764ad8ded56ca0683 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -7442,7 +7442,14 @@ 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.
@@ -7468,7 +7475,12 @@ 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 cd3f7a96c0dfa47b07a710c5f7af6561329beb94..eadffc168614dd90ff9e606dbacbfb7be56c9791 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-09-15  Jakub Jelinek  <jakub@redhat.com>
+
+       PR rtl-optimization/82192
+       * gcc.c-torture/execute/pr82192.c: New test.
+
 2017-09-15  Richard Biener  <rguenther@suse.de>
 
        PR tree-optimization/82217

diff --git a/gcc/testsuite/gcc.c-torture/execute/pr82192.c b/gcc/testsuite/gcc.c-torture/execute/pr82192.c
new file mode 100644 (file)
index 0000000..9e56e20
--- /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;
+}