From: Alexander Monakov <amonakov@ispras.ru>
Date: Tue, 23 Aug 2022 15:42:24 +0000 (+0300)
Subject: i386: avoid zero extension for crc32q
X-Git-Tag: Thesis~3943
X-Git-Url: https://gcc.gnu.org/git/?a=commitdiff_plain;h=810d9815249451f477d4cbc67b8e4a0819c37faa;p=gcc.git

i386: avoid zero extension for crc32q

The crc32q instruction takes 64-bit operands, but ignores high 32 bits
of the destination operand, and zero-extends the result from 32 bits.

Let's model this in the RTL pattern to avoid zero-extension when the
_mm_crc32_u64 intrinsic is used with a 32-bit type.

	PR target/106453

gcc/ChangeLog:

	* config/i386/i386.md (sse4_2_crc32di): Model that only low 32
	bits of operand 0 are consumed, and the result is zero-extended
	to 64 bits.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr106453.c: New test.
---

diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 1aef1af594d8..1be9b669909b 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -23823,10 +23823,11 @@
 
 (define_insn "sse4_2_crc32di"
   [(set (match_operand:DI 0 "register_operand" "=r")
-	(unspec:DI
-	  [(match_operand:DI 1 "register_operand" "0")
-	   (match_operand:DI 2 "nonimmediate_operand" "rm")]
-	  UNSPEC_CRC32))]
+	(zero_extend:DI
+	  (unspec:SI
+	    [(match_operand:SI 1 "register_operand" "0")
+	     (match_operand:DI 2 "nonimmediate_operand" "rm")]
+	  UNSPEC_CRC32)))]
   "TARGET_64BIT && TARGET_CRC32"
   "crc32{q}\t{%2, %0|%0, %2}"
   [(set_attr "type" "sselog1")
diff --git a/gcc/testsuite/gcc.target/i386/pr106453.c b/gcc/testsuite/gcc.target/i386/pr106453.c
new file mode 100644
index 000000000000..bd2e7282cf6b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr106453.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2 -mcrc32 -dp" } */
+/* { dg-final { scan-assembler-not "zero_extendsidi" } } */
+
+#include <immintrin.h>
+#include <stdint.h>
+
+uint32_t f(uint32_t c, uint64_t *p, size_t n)
+{
+    for (size_t i = 0; i < n; i++)
+        c = _mm_crc32_u64(c, p[i]);
+    return c;
+}