combine.c (simplify_comparison, [...]): Do not drop the extend if we'd have to add a paradoxical subreg later.

gcc/ChangeLog:
* combine.c (simplify_comparison, case SIGN_EXTEND, ZERO_EXTEND):
Do not drop the extend if we'd have to add a paradoxical subreg
later.  Include optabs.h and insn-codes.h.
* Makefile.in (combine.o): Depend on $(OPTABS_H).
gcc/testsuite/ChangeLog:
* gcc.c-torture/execute/20050203-1.c: New.

From-SVN: r94655

5 files changed, 64 insertions, 15 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b9a6395..f011c4e 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2005-02-03  Alexandre Oliva  <aoliva@redhat.com>
+
+	* combine.c (simplify_comparison, case SIGN_EXTEND, ZERO_EXTEND):
+	Do not drop the extend if we'd have to add a paradoxical subreg
+	later.  Include optabs.h and insn-codes.h.
+	* Makefile.in (combine.o): Depend on $(OPTABS_H).
+
 2005-02-02  Roger Sayle  <roger@eyesopen.com>
 
 	PR middle-end/19405
diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 288c269..44a954a 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -2046,7 +2046,7 @@ et-forest.o : et-forest.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) et-forest.
 combine.o : combine.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
    $(FLAGS_H) function.h insn-config.h $(INSN_ATTR_H) $(REGS_H) $(EXPR_H) \
    rtlhooks-def.h $(BASIC_BLOCK_H) $(RECOG_H) real.h hard-reg-set.h \
-   toplev.h $(TM_P_H) $(TREE_H) $(TARGET_H) output.h $(PARAMS_H)
+   toplev.h $(TM_P_H) $(TREE_H) $(TARGET_H) output.h $(PARAMS_H) $(OPTABS_H)
 regclass.o : regclass.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
    hard-reg-set.h $(FLAGS_H) $(BASIC_BLOCK_H) $(REGS_H) insn-config.h \
    $(RECOG_H) reload.h real.h toplev.h function.h output.h $(GGC_H) \
diff --git a/gcc/combine.c b/gcc/combine.c
index 6badd28..ae773b9 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -90,6 +90,8 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 #include "real.h"
 #include "toplev.h"
 #include "target.h"
+#include "optabs.h"
+#include "insn-codes.h"
 #include "rtlhooks-def.h"
 /* Include output.h for dump_file.  */
 #include "output.h"
@@ -10054,16 +10056,22 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
 	  break;
 
 	case SIGN_EXTEND:
-	  /* Can simplify (compare (zero/sign_extend FOO) CONST)
-	     to (compare FOO CONST) if CONST fits in FOO's mode and we
-	     are either testing inequality or have an unsigned comparison
-	     with ZERO_EXTEND or a signed comparison with SIGN_EXTEND.  */
-	  if (! unsigned_comparison_p
-	      && (GET_MODE_BITSIZE (GET_MODE (XEXP (op0, 0)))
-		  <= HOST_BITS_PER_WIDE_INT)
+	  /* Can simplify (compare (zero/sign_extend FOO) CONST) to
+	     (compare FOO CONST) if CONST fits in FOO's mode and we
+	     are either testing inequality or have an unsigned
+	     comparison with ZERO_EXTEND or a signed comparison with
+	     SIGN_EXTEND.  But don't do it if we don't have a compare
+	     insn of the given mode, since we'd have to revert it
+	     later on, and then we wouldn't know whether to sign- or
+	     zero-extend.  */
+	  mode = GET_MODE (XEXP (op0, 0));
+	  if (mode != VOIDmode && GET_MODE_CLASS (mode) == MODE_INT
+	      && ! unsigned_comparison_p
+	      && (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
 	      && ((unsigned HOST_WIDE_INT) const_op
-		  < (((unsigned HOST_WIDE_INT) 1
-		      << (GET_MODE_BITSIZE (GET_MODE (XEXP (op0, 0))) - 1)))))
+		  < (((unsigned HOST_WIDE_INT) 1 
+		      << (GET_MODE_BITSIZE (mode) - 1))))
+	      && cmp_optab->handlers[(int) mode].insn_code != CODE_FOR_nothing)
 	    {
 	      op0 = XEXP (op0, 0);
 	      continue;
@@ -10139,11 +10147,12 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
 	  /* ... fall through ...  */
 
 	case ZERO_EXTEND:
-	  if ((unsigned_comparison_p || equality_comparison_p)
-	      && (GET_MODE_BITSIZE (GET_MODE (XEXP (op0, 0)))
-		  <= HOST_BITS_PER_WIDE_INT)
-	      && ((unsigned HOST_WIDE_INT) const_op
-		  < GET_MODE_MASK (GET_MODE (XEXP (op0, 0)))))
+	  mode = GET_MODE (XEXP (op0, 0));
+	  if (mode != VOIDmode && GET_MODE_CLASS (mode) == MODE_INT
+	      && (unsigned_comparison_p || equality_comparison_p)
+	      && (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
+	      && ((unsigned HOST_WIDE_INT) const_op < GET_MODE_MASK (mode))
+	      && cmp_optab->handlers[(int) mode].insn_code != CODE_FOR_nothing)
 	    {
 	      op0 = XEXP (op0, 0);
 	      continue;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e632b52..3820b90 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2005-02-03  Alexandre Oliva  <aoliva@redhat.com>
+
+	* gcc.c-torture/execute/20050203-1.c: New.
+
 2005-02-03  Dorit Naishlos  <dorit@il.ibm.com>
 
 	* gcc.dg/vect/vect-85.c: Remove xfail.
diff --git a/gcc/testsuite/gcc.c-torture/execute/20050203-1.c b/gcc/testsuite/gcc.c-torture/execute/20050203-1.c
new file mode 100644
index 0000000..0b38277
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/20050203-1.c
@@ -0,0 +1,29 @@
+/* Reduced testcase extracted from Samba source code.  */
+
+#include <stdlib.h>
+
+static void __attribute__((__noinline__))
+     foo (unsigned char *p) {
+  *p = 0x81;
+}
+
+static void __attribute__((__noinline__))
+     bar (int x) {
+  asm ("");
+}
+
+int main() {
+  unsigned char b;
+
+  foo(&b);
+  if (b & 0x80)
+    {
+      bar (b & 0x7f);
+      exit (0);
+    }
+  else
+    {
+      bar (b & 1);
+      abort ();
+    }
+}