[gcc r16-3987] [RISC-V][PR target/121983] Fix unprotected REGNO invocation

[Jeff Law]

https://gcc.gnu.org/g:cc0959221ee2a6f17dda6335bb1615207e2c8e51

commit r16-3987-gcc0959221ee2a6f17dda6335bb1615207e2c8e51
Author: Jeff Law <jlaw@ventanamicro.com>
Date:   Fri Sep 19 09:17:01 2025 -0600

    [RISC-V][PR target/121983] Fix unprotected REGNO invocation
    
    So this was a naked REGNO usage, which of course blows up if RTL checking is
    enabled and something else sneaks in (SUBREG).   Thankfully it never results in
    incorrect code, though I could theorize it could cause a bootstrap comparison
    failure in the "right" circumstances.
    
    Bootstrapped & regression tested on the Pioneer.  Also regression tested on
    riscv64-elf and riscv32-elf.   I'll push to the trunk once pre-commit CI is
    done.
    
    jeff
    
            PR target/121983
    gcc/
            * config/riscv/riscv.cc (riscv_macro_fusion_pair_p): Make sure
            object is a REG before asking for its REGNO.  Fix a trivial
            whitespace nit.
    
    gcc/testsuite/
            * gcc.target/riscv/pr121983.c: New test.

Diff:
---
 gcc/config/riscv/riscv.cc                 | 11 +++++++++--
 gcc/testsuite/gcc.target/riscv/pr121983.c | 15 +++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 572da2d9f83e..b95333897df8 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -10369,6 +10369,7 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn *curr)
 	  && GET_CODE (SET_SRC (curr_set)) == LSHIFTRT
 	  && REG_P (SET_DEST (prev_set))
 	  && REG_P (SET_DEST (curr_set))
+	  && REG_P (XEXP (SET_SRC (curr_set), 0))
 	  && REGNO (XEXP (SET_SRC (curr_set), 0)) == curr_dest_regno
 	  && CONST_INT_P (XEXP (SET_SRC (prev_set), 1))
 	  && CONST_INT_P (XEXP (SET_SRC (curr_set), 1))
@@ -10397,6 +10398,7 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn *curr)
 	  && GET_CODE (SET_SRC (curr_set)) == LSHIFTRT
 	  && REG_P (SET_DEST (prev_set))
 	  && REG_P (SET_DEST (curr_set))
+	  && REG_P (XEXP (SET_SRC (curr_set), 0))
 	  && REGNO (XEXP (SET_SRC (curr_set), 0)) == curr_dest_regno
 	  && CONST_INT_P (XEXP (SET_SRC (prev_set), 1))
 	  && CONST_INT_P (XEXP (SET_SRC (curr_set), 1))
@@ -10421,6 +10423,7 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn *curr)
       if (MEM_P (SET_SRC (curr_set))
 	  && SCALAR_INT_MODE_P (GET_MODE (SET_DEST (curr_set)))
 	  && REG_P (XEXP (SET_SRC (curr_set), 0))
+	  && REG_P (XEXP (SET_SRC (curr_set), 0))
 	  && REGNO (XEXP (SET_SRC (curr_set), 0)) == prev_dest_regno
 	  && GET_CODE (SET_SRC (prev_set)) == PLUS
 	  && REG_P (XEXP (SET_SRC (prev_set), 0))
@@ -10481,6 +10484,7 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn *curr)
       if (MEM_P (SET_SRC (curr_set))
 	  && SCALAR_INT_MODE_P (GET_MODE (SET_DEST (curr_set)))
 	  && GET_CODE (XEXP (SET_SRC (curr_set), 0)) == PLUS
+	  && REG_P (XEXP (XEXP (SET_SRC (curr_set), 0), 0))
 	  && REGNO (XEXP (XEXP (SET_SRC (curr_set), 0), 0)) == prev_dest_regno)
 	{
 	  if (riscv_set_is_add (prev_set))
@@ -10539,8 +10543,8 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn *curr)
 	  && MEM_P (XEXP (SET_SRC (curr_set), 0))
 	  && SCALAR_INT_MODE_P (GET_MODE (SET_DEST (curr_set)))
 	  && GET_CODE (XEXP (XEXP (SET_SRC (curr_set), 0), 0)) == PLUS
-	  && REG_P (XEXP (XEXP (XEXP (SET_SRC (curr_set), 0), 0),0))
-	  && (REGNO (XEXP (XEXP (XEXP (SET_SRC (curr_set), 0), 0),0))
+	  && REG_P (XEXP (XEXP (XEXP (SET_SRC (curr_set), 0), 0), 0))
+	  && (REGNO (XEXP (XEXP (XEXP (SET_SRC (curr_set), 0), 0), 0))
 	      == prev_dest_regno))
 	{
 	  if (riscv_set_is_adduw (prev_set))
@@ -10672,6 +10676,7 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn *curr)
 	  && MEM_P (SET_SRC (curr_set))
 	  && SCALAR_INT_MODE_P (GET_MODE (SET_DEST (curr_set)))
 	  && GET_CODE (XEXP (SET_SRC (curr_set), 0)) == PLUS
+	  && REG_P (XEXP (XEXP (SET_SRC (curr_set), 0), 0))
 	  && REGNO (XEXP (XEXP (SET_SRC (curr_set), 0), 0)) == prev_dest_regno)
 	{
 	  if (dump_file)
@@ -10683,6 +10688,7 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn *curr)
 	  && MEM_P (SET_SRC (curr_set))
 	  && SCALAR_INT_MODE_P (GET_MODE (SET_DEST (curr_set)))
 	  && GET_CODE (XEXP (SET_SRC (curr_set), 0)) == LO_SUM
+	  && REG_P (XEXP (XEXP (SET_SRC (curr_set), 0), 0))
 	  && REGNO (XEXP (XEXP (SET_SRC (curr_set), 0), 0)) == prev_dest_regno)
 	{
 	  if (dump_file)
@@ -10696,6 +10702,7 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn *curr)
 	  && MEM_P (XEXP (SET_SRC (curr_set), 0))
 	  && SCALAR_INT_MODE_P (GET_MODE (SET_DEST (curr_set)))
 	  && (GET_CODE (XEXP (XEXP (SET_SRC (curr_set), 0), 0)) == LO_SUM
+	      && REG_P (XEXP (XEXP (XEXP (SET_SRC (curr_set), 0), 0), 0))
 	      && (REGNO (XEXP (XEXP (XEXP (SET_SRC (curr_set), 0), 0), 0))
 		  == prev_dest_regno)))
 	{
diff --git a/gcc/testsuite/gcc.target/riscv/pr121983.c b/gcc/testsuite/gcc.target/riscv/pr121983.c
new file mode 100644
index 000000000000..1572c379a038
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr121983.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-mcpu=xiangshan-nanhu" } */
+
+struct {
+  int a;
+  short s;
+  unsigned x : 18;
+  unsigned y : 14;
+} bf;
+
+void
+foo()
+{
+  bf.s ^= bf.y / __builtin_stdc_rotate_left(bf.x, 5);
+}