i386: Optimize lea with zero-extend. [PR 101716]

For ASHIFT + ZERO_EXTEND pattern, combine pass failed to
match it to lea since it will generate non-canonical
zero-extend. Adjust predicate and cost_model to allow combine
for lea.

gcc/ChangeLog:

	PR target/101716
	* config/i386/i386.c (ix86_live_on_entry): Adjust comment.
	(ix86_decompose_address): Remove retval check for ASHIFT,
	allow non-canonical zero extend if AND mask covers ASHIFT
	count.
	(ix86_legitimate_address_p): Adjust condition for decompose.
	(ix86_rtx_costs): Adjust cost for lea with non-canonical
	zero-extend.

	Co-Authored by: Uros Bizjak <ubizjak@gmail.com>

gcc/testsuite/ChangeLog:

	PR target/101716
	* gcc.target/i386/pr101716.c: New test.

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index ebec8668758e3e80257b0a144c73f9205a9d95a4..ddbbbceded160d559e9cbd273cf1756ea858b32b 100644 (file)
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -10018,8 +10018,7 @@ ix86_live_on_entry (bitmap regs)
 \f
 /* Extract the parts of an RTL expression that is a valid memory address
    for an instruction.  Return 0 if the structure of the address is
-   grossly off.  Return -1 if the address contains ASHIFT, so it is not
-   strictly valid, but still used for computing length of lea instruction.  */
+   grossly off.  */
 
 int
 ix86_decompose_address (rtx addr, struct ix86_address *out)
@@ -10029,7 +10028,6 @@ ix86_decompose_address (rtx addr, struct ix86_address *out)
   HOST_WIDE_INT scale = 1;
   rtx scale_rtx = NULL_RTX;
   rtx tmp;
-  int retval = 1;
   addr_space_t seg = ADDR_SPACE_GENERIC;
 
   /* Allow zero-extended SImode addresses,
@@ -10053,6 +10051,27 @@ ix86_decompose_address (rtx addr, struct ix86_address *out)
          if (CONST_INT_P (addr))
            return 0;
        }
+      else if (GET_CODE (addr) == AND)
+       {
+         /* For ASHIFT inside AND, combine will not generate
+            canonical zero-extend. Merge mask for AND and shift_count
+            to check if it is canonical zero-extend.  */
+         tmp = XEXP (addr, 0);
+         rtx mask = XEXP (addr, 1);
+         if (tmp && GET_CODE(tmp) == ASHIFT)
+           {
+             rtx shift_val = XEXP (tmp, 1);
+             if (CONST_INT_P (mask) && CONST_INT_P (shift_val)
+                 && (((unsigned HOST_WIDE_INT) INTVAL(mask)
+                     | ((HOST_WIDE_INT_1U << INTVAL(shift_val)) - 1))
+                     == 0xffffffff))
+               {
+                 addr = lowpart_subreg (SImode, XEXP (addr, 0),
+                                        DImode);
+               }
+           }
+
+       }
     }
 
   /* Allow SImode subregs of DImode addresses,
@@ -10179,7 +10198,6 @@ ix86_decompose_address (rtx addr, struct ix86_address *out)
       if ((unsigned HOST_WIDE_INT) scale > 3)
        return 0;
       scale = 1 << scale;
-      retval = -1;
     }
   else
     disp = addr;                       /* displacement */
@@ -10252,7 +10270,7 @@ ix86_decompose_address (rtx addr, struct ix86_address *out)
   out->scale = scale;
   out->seg = seg;
 
-  return retval;
+  return 1;
 }
 \f
 /* Return cost of the memory address x.
@@ -10765,7 +10783,7 @@ ix86_legitimate_address_p (machine_mode, rtx addr, bool strict)
   HOST_WIDE_INT scale;
   addr_space_t seg;
 
-  if (ix86_decompose_address (addr, &parts) <= 0)
+  if (ix86_decompose_address (addr, &parts) == 0)
     /* Decomposition failed.  */
     return false;
 
@@ -20419,6 +20437,12 @@ ix86_rtx_costs (rtx x, machine_mode mode, int outer_code_i, int opno,
                       << (GET_MODE (XEXP (x, 1)) != DImode)));
          return true;
        }
+      else if (code == AND
+              && address_no_seg_operand (x, mode))
+       {
+         *total = cost->lea;
+         return true;
+       }
       /* FALLTHRU */
 
     case NEG:

diff --git a/gcc/testsuite/gcc.target/i386/pr101716.c b/gcc/testsuite/gcc.target/i386/pr101716.c
new file mode 100644 (file)
index 0000000..5e3ea64
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr101716.c
@@ -0,0 +1,11 @@
+/* PR target/101716 */
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2" } */
+
+/* { dg-final { scan-assembler "leal\[\\t \]\[^\\n\]*eax" } } */
+/* { dg-final { scan-assembler-not "movl\[\\t \]\[^\\n\]*eax" } } */
+
+unsigned long long sample1(unsigned long long m) {
+    unsigned int t = -1;
+    return (m << 1) & t;
+}