Merge lp:~michaelh1/gcc-linaro/combine-best-cc into lp:gcc-linaro/4.6

[Michael Hope]

Backport trunk r171304.

Fixes a bug in __builtin_isgreaterequal.

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cbuild-ancestor: lp:gcc-linaro/4.6+bzr106768
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The test suite results were unchanged compared to the branch point lp:gcc-linaro/4.6+bzr106768.

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The test suite results were unchanged compared to the branch point lp:gcc-linaro/4.6+bzr106768.

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cbuild-checked: x86_64-natty-cbuild158-oort1-x86_64r1

[Richard Sandiford (rsandifo)]

OK

review: Approve

=== modified file 'ChangeLog.linaro'
--- ChangeLog.linaro	2011-07-07 13:15:23 +0000
+++ ChangeLog.linaro	2011-07-11 04:14:29 +0000
@@ -1,3 +1,13 @@
[phone]  Michael Hope  <[e-mail]>
+
+	gcc/
+	Backport from mainline:
+
+	2011-03-22  Eric Botcazou  <[e-mail]>
+
+	* combine.c (simplify_set): Try harder to find the best CC mode when
+	simplifying a nested COMPARE on the RHS.
+
 2011-07-07  Richard Sandiford  <[e-mail]>
 
 	gcc/

=== modified file 'gcc/combine.c'
--- gcc/combine.c	2011-05-27 14:31:18 +0000
+++ gcc/combine.c	2011-07-11 04:14:29 +0000
@@ -6287,10 +6287,18 @@
       enum rtx_code new_code;
       rtx op0, op1, tmp;
       int other_changed = 0;
+      rtx inner_compare = NULL_RTX;
       enum machine_mode compare_mode = GET_MODE (dest);
 
       if (GET_CODE (src) == COMPARE)
-	op0 = XEXP (src, 0), op1 = XEXP (src, 1);
+	{
+	  op0 = XEXP (src, 0), op1 = XEXP (src, 1);
+	  if (GET_CODE (op0) == COMPARE && op1 == const0_rtx)
+	    {
+	      inner_compare = op0;
+	      op0 = XEXP (inner_compare, 0), op1 = XEXP (inner_compare, 1);
+	    }
+	}
       else
 	op0 = src, op1 = CONST0_RTX (GET_MODE (src));
 
@@ -6332,6 +6340,12 @@
 	 need to use a different CC mode here.  */
       if (GET_MODE_CLASS (GET_MODE (op0)) == MODE_CC)
 	compare_mode = GET_MODE (op0);
+      else if (inner_compare
+	       && GET_MODE_CLASS (GET_MODE (inner_compare)) == MODE_CC
+	       && new_code == old_code
+	       && op0 == XEXP (inner_compare, 0)
+	       && op1 == XEXP (inner_compare, 1))
+	compare_mode = GET_MODE (inner_compare);
       else
 	compare_mode = SELECT_CC_MODE (new_code, op0, op1);