combine.c (simplify_if_then_else): Simplify IF_THEN_ELSE that isolates a single bit...

gcc:
* combine.c (simplify_if_then_else): Simplify IF_THEN_ELSE
that isolates a single bit, even if the condition involves
subregs.

From-SVN: r242917

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5cf1698..83615ed 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2016-11-28  Paolo Bonzini  <bonzini@gnu.org>
+
+       * combine.c (simplify_if_then_else): Simplify IF_THEN_ELSE
+       that isolates a single bit, even if the condition involves
+       subregs.
+
 2016-11-28  Tamar Christina  <tamar.christina@arm.com>
 
        * config/aarch64/aarch64-simd-builtins.def

diff --git a/gcc/combine.c b/gcc/combine.c
index ecf6741..45d4048 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -6522,14 +6522,22 @@ simplify_if_then_else (rtx x)
       simplify_shift_const (NULL_RTX, ASHIFT, mode,
                            gen_lowpart (mode, XEXP (cond, 0)), i);
 
-  /* (IF_THEN_ELSE (NE REG 0) (0) (8)) is REG for nonzero_bits (REG) == 8.  */
+  /* (IF_THEN_ELSE (NE A 0) C1 0) is A or a zero-extend of A if the only
+     non-zero bit in A is C1.  */
   if (true_code == NE && XEXP (cond, 1) == const0_rtx
       && false_rtx == const0_rtx && CONST_INT_P (true_rtx)
-      && GET_MODE (XEXP (cond, 0)) == mode
+      && INTEGRAL_MODE_P (GET_MODE (XEXP (cond, 0)))
       && (UINTVAL (true_rtx) & GET_MODE_MASK (mode))
-         == nonzero_bits (XEXP (cond, 0), mode)
+         == nonzero_bits (XEXP (cond, 0), GET_MODE (XEXP (cond, 0)))
       && (i = exact_log2 (UINTVAL (true_rtx) & GET_MODE_MASK (mode))) >= 0)
-    return XEXP (cond, 0);
+    {
+      rtx val = XEXP (cond, 0);
+      enum machine_mode val_mode = GET_MODE (val);
+      if (val_mode == mode)
+        return val;
+      else if (GET_MODE_PRECISION (val_mode) < GET_MODE_PRECISION (mode))
+        return simplify_gen_unary (ZERO_EXTEND, mode, val, val_mode);
+    }
 
   return x;
 }