[PATCH] Fix up ix86_avoid_lea_for_addr (PR target/59880)

Jakub Jelinek jakub@redhat.com
Mon Jan 20 08:38:00 GMT 2014


Hi!

As mentioned in the PR or even in the comment below, ix86_decompose_address
sometimes sets parts.base to some REG and parts.disp to const0_rtx, even
when the operands aren't of a lea insn, but normal or zero extending mov.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2014-01-20  Jakub Jelinek  <jakub@redhat.com>

	PR target/59880
	* config/i386/i386.c (ix86_avoid_lea_for_addr): Return false
	if operands[1] is a REG or ZERO_EXTEND of a REG.

	* gcc.target/i386/pr59880.c: New test.

--- gcc/config/i386/i386.c.jj	2014-01-19 12:18:49.000000000 +0100
+++ gcc/config/i386/i386.c	2014-01-19 19:02:34.078168289 +0100
@@ -18159,8 +18159,19 @@ ix86_avoid_lea_for_addr (rtx insn, rtx o
   if (!TARGET_AVOID_LEA_FOR_ADDR || optimize_function_for_size_p (cfun))
     return false;
 
+  /* The "at least two components" test below might not catch simple
+     *mov[sd]i_internal or *zero_extendsidi2 insns if parts.base is
+     non-NULL and parts.disp is const0_rtx as the only components in
+     the address, e.g. if the register is %rbp or %r13.  As this
+     test is much cheaper and moves or zero extensions are the common
+     case, do this check first.  */
+  if (REG_P (operands[1])
+      || (GET_CODE (operands[1]) == ZERO_EXTEND
+	  && REG_P (XEXP (operands[1], 0))))
+    return false;
+
   /* Check it is correct to split here.  */
-  if (!ix86_ok_to_clobber_flags(insn))
+  if (!ix86_ok_to_clobber_flags (insn))
     return false;
 
   ok = ix86_decompose_address (operands[1], &parts);
--- gcc/testsuite/gcc.target/i386/pr59880.c.jj	2014-01-19 19:24:44.094382629 +0100
+++ gcc/testsuite/gcc.target/i386/pr59880.c	2014-01-19 19:25:30.000000000 +0100
@@ -0,0 +1,14 @@
+/* PR target/59880 */
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2 -mtune=silvermont" } */
+
+register unsigned int r13 __asm ("r13");
+unsigned long long
+foo (void)
+{
+  return r13;
+}
+
+/* Ensure we don't emit a useless zero-extension after another
+   zero-extension.  */
+/* { dg-final { scan-assembler-not "%eax, %eax" } } */

	Jakub



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