RE: [RFC, PATCH][LRA, MIPS] ICE: in decompose_normal_address, at rtlanal.c:5817

[Robert Suchanek <Robert dot Suchanek at imgtec dot com>]

Hi Steven/Vladimir,

> It's hard to say what the correct fix should be, but it sounds like
> the address you get after the substitutions should be simplified
> (folded).

Coming back to the original testcase and re-analyzing the problem, it appears
that there is, indeed, a missing case for simplification of LO_SUM/HIGH pair.
The patch attached resolves the issue.

Although the testcase is not reproducible on the trunk, I think it is still
worth to include it in case the ICE reoccurred.

The patch has been bootstrapped and regtested on x86_64-unknown-linux-gnu target
and similarly tested against SVN revision r212763 where it can be reproduced.

Regards,
Robert

2015-01-08  Robert Suchanek  <robert.suchanek@imgtec.com>

gcc/
	* simplify-rtx.c (simplify_replace_fn_rtx): Simplify (lo_sum (high x)
	(const (plus x offset))) to (const (plus x offset)).

gcc/testsuite/
	* gcc.target/mips/20150108.c: New test.
---
 gcc/simplify-rtx.c                       |    6 ++++++
 gcc/testsuite/gcc.target/mips/20150108.c |   25 +++++++++++++++++++++++++
 2 files changed, 31 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/mips/20150108.c

diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 04af01e..7621316 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -503,6 +503,12 @@ simplify_replace_fn_rtx (rtx x, const_rtx old_rtx,
 	  if (GET_CODE (op0) == HIGH && rtx_equal_p (XEXP (op0, 0), op1))
 	    return op1;
 
+	  /* (lo_sum (high x) (const (plus x ofs))) -> (const (plus x ofs))  */
+	  if (GET_CODE (op0) == HIGH && GET_CODE (op1) == CONST
+	      && GET_CODE(XEXP (op1, 0)) == PLUS
+	      && rtx_equal_p (XEXP (XEXP (op1, 0), 0), XEXP (op0, 0)))
+	    return op1;
+
 	  if (op0 == XEXP (x, 0) && op1 == XEXP (x, 1))
 	    return x;
 	  return gen_rtx_LO_SUM (mode, op0, op1);
diff --git a/gcc/testsuite/gcc.target/mips/20150108.c b/gcc/testsuite/gcc.target/mips/20150108.c
new file mode 100644
index 0000000..f18dbe7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/20150108.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-mips32r2" } */
+
+long long a[10];
+long long b, c, d, k, m, n, o, p, q, r, s, t, u, v, w;
+int e, f, g, h, i, j, l, x;
+
+NOMIPS16 fn1() {
+  for (; x; x++)
+    if (x & 1)
+      s = h | g;
+    else
+      s = f | e;
+  l = ~0;
+  m = 1 | k;
+  n = i;
+  o = j;
+  p = f | e;
+  q = h | g;
+  w = d | c | a[1];
+  t = c;
+  v = b | c;
+  u = v;
+  r = b | a[4];
+}
-- 
1.7.9.5