[i386] Improve "mov<mode>cc" expander for DImode immediates [PR120553]

"mov<mode>cc" expander uses x86_64_general_operand predicate that limits the
range of immediate operands to 32-bit size.  The usage of this predicate
causes ifcvt to force out-of-range immediates to registers when converting
through noce_try_cmove.  The testcase:

long long foo (long long c) { return c >= 0 ? 0x400000000ll : -1ll; }

compiles (-O2) to:

foo:
	testq	%rdi, %rdi
	movq	$-1, %rax
	movabsq	$0x400000000, %rdx
	cmovns	%rdx, %rax
	ret

The above testcase can be compiled to a more optimized code without
problematic CMOV instruction if 64-bit immediates are allowed in
"mov<mode>cc" expander:

foo:
	movq	%rdi, %rax
	sarq	$63, %rax
	btsq	$34, %rax
	ret

The expander calls the ix86_expand_int_movcc function which internally
sanitizes arguments of emitted logical insns using expand_simple_binop.
The out-of-range immediates are forced to a temporary register just
before the instruction, so the instruction combiner is then able to
synthesize 64-bit BTS instruction.

The code improves even for non-exact-log2 64-bit immediates, e.g.

long long foo (long long c) { return c >= 0 ? 0x400001234ll : -1ll; }

that now compiles to:

foo:
        movabsq $0x400001234, %rdx
        movq    %rdi, %rax
        sarq    $63, %rax
        orq     %rdx, %rax
        ret

again avoiding problematic CMOV instruction.

	PR target/120553

gcc/ChangeLog:

	* config/i386/i386.md (mov<mode>cc): Use "general_operand"
	predicate for operands 2 and 3 for all modes.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr120553.c: New test.

diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 40b43cf092acc0c84ad514540b411959b0760d6c..8eee44756eba707790d937afc1bbc97843c9819a 100644 (file)
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -26478,8 +26478,8 @@
 (define_expand "mov<mode>cc"
   [(set (match_operand:SWIM 0 "register_operand")
        (if_then_else:SWIM (match_operand 1 "comparison_operator")
-                          (match_operand:SWIM 2 "<general_operand>")
-                          (match_operand:SWIM 3 "<general_operand>")))]
+                          (match_operand:SWIM 2 "general_operand")
+                          (match_operand:SWIM 3 "general_operand")))]
   ""
   "if (ix86_expand_int_movcc (operands)) DONE; else FAIL;")
 

diff --git a/gcc/testsuite/gcc.target/i386/pr120553.c b/gcc/testsuite/gcc.target/i386/pr120553.c
new file mode 100644 (file)
index 0000000..abbf58c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr120553.c
@@ -0,0 +1,6 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2" } */
+
+long long foo (long long c) { return c >= 0 ? 0x400000000ll : -1ll; }
+
+/* { dg-final { scan-assembler "bts" } } */