From: "Roger Sayle" <roger@nextmovesoftware.com>
To: <gcc-patches@gcc.gnu.org>
Subject: [x86_64 PATCH] Allow any immediate constant in *cmp<dwi>_doubleword splitter.
Date: Fri, 5 Aug 2022 14:14:14 +0100 [thread overview]
Message-ID: <014501d8a8cd$43413aa0$c9c3afe0$@nextmovesoftware.com> (raw)
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This patch tweaks i386.md's *cmp<dwi>_doubleword splitter's predicate to
allow general_operand, not just x86_64_hilo_general_operand, to improve
code generation. As a general rule, i386.md's _doubleword splitters should
be post-reload splitters that require integer immediate operands to be
x86_64_hilo_int_operand, so that each part is a valid word mode immediate
constant. As an exception to this rule, doubleword patterns that must be
split before reload, because they require additional scratch registers,
can take advantage of this ability to create new pseudos, to accept
any immediate constant, and call force_reg on the high and/or low parts
if they are not suitable immediate operands in word mode.
The benefit is shown in the new cmpti3.c test case below.
__int128 x;
int foo()
{
__int128 t = 0x1234567890abcdefLL;
return x == t;
}
where GCC with -O2 currently generates:
movabsq $1311768467294899695, %rax
xorl %edx, %edx
xorq x(%rip), %rax
xorq x+8(%rip), %rdx
orq %rdx, %rax
sete %al
movzbl %al, %eax
ret
but with this patch now generates:
movabsq $1311768467294899695, %rax
xorq x(%rip), %rax
orq x+8(%rip), %rax
sete %al
movzbl %al, %eax
ret
This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
and make -k check, both with and without --target_board=unix{-m32},
with no new failures. The first two new test cases aren't affected
by this patch, but as I had them in my directory, it seemed reasonable to
increase the testsuite's coverage of TImode comparison code generation.
Ok for mainline?
2022-08-05 Roger Sayle <roger@nextmovesoftware.com>
gcc/ChangeLog
* config/i386/i386.md (*cmp<dwi>_doubleword): Change predicate
for x86_64_hilo_general_operand to general operand. Call
force_reg on parts that are not x86_64_immediate_operand.
gcc/testsuite/ChangeLog
* gcc.target/i386/cmpti1.c: New test case.
* gcc.target/i386/cmpti2.c: Likewise.
* gcc.target/i386/cmpti3.c: Likewise.
Thanks in advance,
Roger
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diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 298e4b3..fd30c57 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -1510,7 +1510,7 @@
(define_insn_and_split "*cmp<dwi>_doubleword"
[(set (reg:CCZ FLAGS_REG)
(compare:CCZ (match_operand:<DWI> 0 "nonimmediate_operand")
- (match_operand:<DWI> 1 "x86_64_hilo_general_operand")))]
+ (match_operand:<DWI> 1 "general_operand")))]
"ix86_pre_reload_split ()"
"#"
"&& 1"
@@ -1544,7 +1544,12 @@
else if (operands[0] == constm1_rtx)
emit_insn (gen_one_cmpl<mode>2 (operands[4], operands[1]));
else
- emit_insn (gen_xor<mode>3 (operands[4], operands[0], operands[1]));
+ {
+ if (CONST_SCALAR_INT_P (operands[1])
+ && !x86_64_immediate_operand (operands[1], <MODE>mode))
+ operands[1] = force_reg (<MODE>mode, operands[1]);
+ emit_insn (gen_xor<mode>3 (operands[4], operands[0], operands[1]));
+ }
if (operands[3] == const0_rtx)
operands[5] = operands[2];
@@ -1558,7 +1563,12 @@
else if (operands[2] == constm1_rtx)
emit_insn (gen_one_cmpl<mode>2 (operands[5], operands[3]));
else
- emit_insn (gen_xor<mode>3 (operands[5], operands[2], operands[3]));
+ {
+ if (CONST_SCALAR_INT_P (operands[3])
+ && !x86_64_immediate_operand (operands[3], <MODE>mode))
+ operands[3] = force_reg (<MODE>mode, operands[3]);
+ emit_insn (gen_xor<mode>3 (operands[5], operands[2], operands[3]));
+ }
}
})
diff --git a/gcc/testsuite/gcc.target/i386/cmpti1.c b/gcc/testsuite/gcc.target/i386/cmpti1.c
new file mode 100644
index 0000000..1c5f121
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/cmpti1.c
@@ -0,0 +1,8 @@
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O2" } */
+int eq(__int128 x, __int128 y) { return x == y; }
+int ne(__int128 x, __int128 y) { return x != y; }
+/* { dg-final { scan-assembler-times "xorq" 4 } } */
+/* { dg-final { scan-assembler-times "setne" 1 } } */
+/* { dg-final { scan-assembler-times "sete" 1 } } */
+
diff --git a/gcc/testsuite/gcc.target/i386/cmpti2.c b/gcc/testsuite/gcc.target/i386/cmpti2.c
new file mode 100644
index 0000000..ad95729
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/cmpti2.c
@@ -0,0 +1,12 @@
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O2" } */
+
+__int128 x;
+__int128 y;
+
+int eq() { return x == y; }
+int ne() { return x != y; }
+
+/* { dg-final { scan-assembler-times "xorq" 4 } } */
+/* { dg-final { scan-assembler-times "setne" 1 } } */
+/* { dg-final { scan-assembler-times "sete" 1 } } */
diff --git a/gcc/testsuite/gcc.target/i386/cmpti3.c b/gcc/testsuite/gcc.target/i386/cmpti3.c
new file mode 100644
index 0000000..302efd2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/cmpti3.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O2" } */
+
+__int128 x;
+int foo()
+{
+ __int128 t = 0x1234567890abcdefLL;
+ return x == t;
+}
+
+/* { dg-final { scan-assembler-times "movabsq" 1 } } */
+/* { dg-final { scan-assembler-times "xorq" 1 } } */
+/* { dg-final { scan-assembler-not "xorl" } } */
next reply other threads:[~2022-08-05 13:14 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-05 13:14 Roger Sayle [this message]
2022-08-06 9:51 ` Uros Bizjak
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