Although this constraint is not currently used for any instructions, it is very
useful for custom instructions. Additionally, some new standard extensions
(not yet upstream), such as `Zilsd` and `Zclsd`, are potential users of this
constraint. Therefore, I believe there is sufficient justification to add it
now.
gcc/ChangeLog:
* config/riscv/constraints.md (R): New constraint.
* doc/md.texi: Document new constraint `R`.
gcc/testsuite/ChangeLog:
* gcc.target/riscv/constraint-R.c: New.
---
gcc/config/riscv/constraints.md | 4 ++++
gcc/doc/md.texi | 3 +++
gcc/testsuite/gcc.target/riscv/constraint-R.c | 23 +++++++++++++++++++
3 files changed, 30 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/riscv/constraint-R.c
diff --git a/gcc/config/riscv/constraints.md b/gcc/config/riscv/constraints.md
index 2dce9832219..ebb71000d12 100644
--- a/gcc/config/riscv/constraints.md
+++ b/gcc/config/riscv/constraints.md
@@ -28,6 +28,10 @@ (define_register_constraint "f" "TARGET_HARD_FLOAT ? FP_REGS
:
(define_register_constraint "j" "SIBCALL_REGS"
"@internal")
+(define_register_constraint "R" "GR_REGS"
+ "Even-odd general purpose register pair."
+ "regno % 2 == 0")
+
;; Avoid using register t0 for JALR's argument, because for some
;; microarchitectures that is a return-address stack hint.
(define_register_constraint "l" "JALR_REGS"
diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index 494a9e14c2a..ae5e31438d6 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -3667,6 +3667,9 @@ RVC general purpose register (x8-x15).
RVC floating-point registers (f8-f15), if available, reuse GPR as FPR when use
zfinx.
+@item R
+Even-odd general purpose register pair.
+
@end table
@item RX---@file{config/rx/constraints.md}
diff --git a/gcc/testsuite/gcc.target/riscv/constraint-R.c
b/gcc/testsuite/gcc.target/riscv/constraint-R.c
new file mode 100644
index 00000000000..cb13d8a1f38
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/constraint-R.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
+/* { dg-final { check-function-bodies "**" "" } } */
+/* { dg-additional-options "-std=gnu99" } */
+
+void foo(int a0, int a1, int a2, int a3, int a4, int a5, int a6, int a7, int
m0, int m1) {
+/*
+** foo:
+** ...
+** addi t1, (a[0246]|s[02468]|t[02]), 1
+** ...
+*/
+ __asm__ volatile("addi t1, %0, 1" : : "R" (a1) : "memory");
+}
+void foo2(int a0, long long a1a2) {
+/*
+** foo2:
+** ...
+** addi t1, (a[0246]|s[02468]|t[02]), 1
+** ...
+*/
+ __asm__ volatile("addi t1, %0, 1" : : "R" (a1a2) : "memory");
+}
--
2.34.1
