[PATCH][AArch64][4.9] Restore recog state after finding pre-madd instruction

[Kyrill Tkachov]

Hi all,

This is the backport of the trunk patch posted at 
https://gcc.gnu.org/ml/gcc-patches/2014-10/msg03019.html.
It is essentially the same content (only the diff context differs).
Jakub, this is a regression fix so, if ok'd, can we get this into 4.9.2 
please?

Bootstrapped and regtested on aarch64-none-linux-gnu.

Thanks,
Kyrill

2014-10-28  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    * config/aarch64/aarch64.c (aarch64_madd_needs_nop): Restore
    recog state after aarch64_prev_real_insn call.

2014-10-28  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    * gcc.target/aarch64/madd_after_asm_1.c: New test.diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 34354d4..52c0471 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -6557,6 +6557,10 @@ aarch64_madd_needs_nop (rtx insn)
     return false;
 
   prev = aarch64_prev_real_insn (insn);
+  /* aarch64_prev_real_insn can call recog_memoized on insns other than INSN.
+     Restore recog state to INSN to avoid state corruption.  */
+  extract_constrain_insn_cached (insn);
+
   if (!prev)
     return false;
 
diff --git a/gcc/testsuite/gcc.target/aarch64/madd_after_asm_1.c b/gcc/testsuite/gcc.target/aarch64/madd_after_asm_1.c
new file mode 100644
index 0000000..523941d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/madd_after_asm_1.c
@@ -0,0 +1,14 @@
+/* { dg-do assemble } */
+/* { dg-options "-O2 -mfix-cortex-a53-835769" } */
+
+int
+test (int a, double b, int c, int d, int e)
+{
+  double result;
+  __asm__ __volatile ("// %0, %1"
+                      : "=w" (result)
+                      : "0" (b)
+                      :    /* No clobbers */
+                      );
+  return c * d + e;
+}