re PR rtl-optimization/8746 (gcc miscompiles Linux kernel ppa driver on x86)

	PR optimization/8746
	* config/i386/i386.md (and promoting splitters): Disable HImode to
	SImode promoting when the sign bit matters and is not preserved, or
	when TARGET_FAST_PREFIX is true. Disable promoting when optimizing
	for size.

From-SVN: r64840

gcc/ChangeLog

+2003-03-25  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+	PR optimization/8746
+	* config/i386/i386.md (and promoting splitters): Disable HImode to
+	SImode promoting when the sign bit matters and is not preserved, or
+	when TARGET_FAST_PREFIX is true. Disable promoting when optimizing
+	for size.
+
 2003-03-24  Kazu Hirata  <kazu@cs.umass.edu>
 
 	* config/h8300/h8300.md (a peephole2): Extend to support loads

gcc/config/i386/i386.md

@@ -17628,6 +17628,10 @@
      operands[2] = gen_lowpart (SImode, operands[2]);
    PUT_MODE (operands[3], SImode);")
 
+; Promote the QImode tests, as i386 has encoding of the AND
+; instruction with 32-bit sign-extended immediate and thus the
+; instruction size is unchanged, except in the %eax case for
+; which it is increased by one byte, hence the ! optimize_size.
 (define_split
   [(set (reg 17)
 	(compare (and (match_operand 1 "aligned_operand" "")
@@ -17636,12 +17640,11 @@
    (set (match_operand 0 "register_operand" "")
 	(and (match_dup 1) (match_dup 2)))]
   "! TARGET_PARTIAL_REG_STALL && reload_completed
-   && ix86_match_ccmode (insn, CCNOmode)
-   && (GET_MODE (operands[0]) == HImode
-       || (GET_MODE (operands[0]) == QImode 
-	   /* Ensure that the operand will remain sign extended immediate.  */
-	   && INTVAL (operands[2]) >= 0
-	   && (TARGET_PROMOTE_QImode || optimize_size)))"
+   /* Ensure that the operand will remain sign-extended immediate.  */
+   && ix86_match_ccmode (insn, INTVAL (operands[2]) >= 0 ? CCNOmode : CCZmode)
+   && ! optimize_size
+   && ((GET_MODE (operands[0]) == HImode && ! TARGET_FAST_PREFIX)
+       || (GET_MODE (operands[0]) == QImode && TARGET_PROMOTE_QImode))"
   [(parallel [(set (reg:CCNO 17)
 		   (compare:CCNO (and:SI (match_dup 1) (match_dup 2))
 			         (const_int 0)))
@@ -17654,17 +17657,20 @@
    operands[0] = gen_lowpart (SImode, operands[0]);
    operands[1] = gen_lowpart (SImode, operands[1]);")
 
-; Don't promote the QImode tests, as i386 don't have encoding of
-; the test instruction with 32bit sign extended immediate and thus
-; the code grows.
+; Don't promote the QImode tests, as i386 doesn't have encoding of
+; the TEST instruction with 32-bit sign-extended immediate and thus
+; the instruction size would at least double, which is not what we
+; want even with ! optimize_size.
 (define_split
   [(set (reg 17)
 	(compare (and (match_operand:HI 0 "aligned_operand" "")
 		      (match_operand:HI 1 "const_int_operand" ""))
 		 (const_int 0)))]
   "! TARGET_PARTIAL_REG_STALL && reload_completed
-   && ix86_match_ccmode (insn, CCNOmode)
-   && GET_MODE (operands[0]) == HImode"
+   /* Ensure that the operand will remain sign-extended immediate.  */
+   && ix86_match_ccmode (insn, INTVAL (operands[1]) >= 0 ? CCNOmode : CCZmode)
+   && ! TARGET_FAST_PREFIX
+   && ! optimize_size"
   [(set (reg:CCNO 17)
 	(compare:CCNO (and:SI (match_dup 0) (match_dup 1))
 		      (const_int 0)))]

gcc/testsuite/ChangeLog

 2003-03-25  Eric Botcazou  <ebotcazou@libertysurf.fr>
 
+	* gcc.dg/i386-signbit-1.c: New test.
+	* gcc.dg/i386-signbit-2.c: New test.
+	* gcc.dg/i386-signbit-3.c: New test.
+
+2003-03-25  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
 	* gcc.dg/ultrasp5.c: Fix options.
 
 2003-03-24  Eric Botcazou  <ebotcazou@libertysurf.fr>

gcc/testsuite/gcc.dg/i386-signbit-1.c

+/* PR optimization/8746 */
+/* { dg-do run { target i?86-*-* } } */
+/* { dg-options "-O1 -mtune=i586" } */
+
+extern void abort (void);
+
+unsigned char r0;
+
+int foo(int x)
+{
+  unsigned char r = x&0xf0;
+
+  if (!(r&0x80))
+  {
+    r0 = r;
+    return 0;
+  }
+  else
+    return 1;
+}
+
+int main(void)
+{
+  if (foo(0x80) != 1)
+    abort();
+
+   return 0;
+}

gcc/testsuite/gcc.dg/i386-signbit-2.c

+/* PR optimization/8746 */
+/* { dg-do run { target i?86-*-* } } */
+/* { dg-options "-O1 -mtune=i586" } */
+
+extern void abort (void);
+
+unsigned short r0;
+
+int foo(int x)
+{
+  unsigned short r = x&0xf000;
+
+  if (!(r&0x8000))
+  {
+    r0 = r;
+    return 0;
+  }
+  else
+    return 1;
+}
+
+int main(void)
+{
+  if (foo(0x8000) != 1)
+    abort();
+
+   return 0;
+}

gcc/testsuite/gcc.dg/i386-signbit-3.c

+/* PR optimization/8746 */
+/* { dg-do run { target i?86-*-* } } */
+/* { dg-options "-O1 -mtune=i586" } */
+
+extern void abort (void);
+
+volatile int j;
+
+void f0() { j=0; }
+void f1() { j=1; }
+
+int foo(int x)
+{
+  if ((short int)(x&0x8000) > (short int)0)
+  {
+    f0();
+    return 0;
+  }
+  else
+  {
+    f1();
+    return 1;
+  }
+}
+
+int main(void)
+{
+  if (foo(0x8000) != 1)
+    abort();
+
+   return 0;
+}