https://gcc.gnu.org/g:a86891525d200c1ae81d9f5f441a5b8e24b647ca
commit r15-8882-ga86891525d200c1ae81d9f5f441a5b8e24b647ca
Author: Richard Earnshaw <rearn...@arm.com>
Date: Tue Mar 25 11:50:30 2025 +0000
arm: add commutative alternatives to <US>mull pattern.
Prior to Armv6, the SMULL and UMULL instructions, which have the form
UMULL Rdlo, Rdhi, Rm, Rs
had an operand restriction such that Rdlo, Rdhi and Rm must all be
different registers. Rs, however can overlap either of the
destination registers. Add some register-tie alternatives to allow
the register allocator to find these forms without having to use
additional register moves.
In addition to this, the test is pretty meaningless on Thumb-1 targets
as the S/UMULL instructions do not exist in a 16-bit encoding. So skip
the test in this case.
gcc/ChangeLog:
* config/arm/arm.md (<US>mull): Add alternatives that allow Rs
to be tied to either Rdlo or Rdhi.
gcc/testsuite/ChangeLog:
* gcc.target/arm/pr42575.c: Skip test if thumb1.
Diff:
---
gcc/config/arm/arm.md | 10 +++++-----
gcc/testsuite/gcc.target/arm/pr42575.c | 1 +
2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index 442d86b93292..597ef6725bb7 100644
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -2432,11 +2432,11 @@
)
(define_insn "<US>mull"
- [(set (match_operand:SI 0 "s_register_operand" "=r,&r")
+ [(set (match_operand:SI 0 "s_register_operand" "=r,&r,&r,&r")
(mult:SI
- (match_operand:SI 2 "s_register_operand" "%r,r")
- (match_operand:SI 3 "s_register_operand" "r,r")))
- (set (match_operand:SI 1 "s_register_operand" "=r,&r")
+ (match_operand:SI 2 "s_register_operand" "%r,r,r,r")
+ (match_operand:SI 3 "s_register_operand" "r,r,0,1")))
+ (set (match_operand:SI 1 "s_register_operand" "=r,&r,&r,&r")
(truncate:SI
(lshiftrt:DI
(mult:DI (SE:DI (match_dup 2)) (SE:DI (match_dup 3)))
@@ -2445,7 +2445,7 @@
"<US>mull%?\\t%0, %1, %2, %3"
[(set_attr "type" "umull")
(set_attr "predicable" "yes")
- (set_attr "arch" "v6,nov6")]
+ (set_attr "arch" "v6,nov6,nov6,nov6")]
)
(define_expand "<Us>maddsidi4"
diff --git a/gcc/testsuite/gcc.target/arm/pr42575.c
b/gcc/testsuite/gcc.target/arm/pr42575.c
index 1998e323df17..3906c77ed569 100644
--- a/gcc/testsuite/gcc.target/arm/pr42575.c
+++ b/gcc/testsuite/gcc.target/arm/pr42575.c
@@ -1,4 +1,5 @@
/* { dg-options "-O2" } */
+/* { dg-skip-if "Thumb1 lacks UMULL" { arm_thumb1 } } */
/* Make sure RA does good job allocating registers and avoids
unnecessary moves. */
/* { dg-final { scan-assembler-not "mov" } } */
