RISC-V: Fix __atomic_compare_exchange with 32 bit value on RV64

atomic_compare_and_swapsi will use lr.w to do obtain the original value,
which sign extends to DI.  RV64 only has DI comparisons, so we also need
to sign extend the expected value to DI as otherwise the comparison will
fail when the expected value has the 32nd bit set.

gcc/ChangeLog:

	PR target/114130
	* config/riscv/sync.md (atomic_compare_and_swap<mode>): Sign
	extend the expected value if needed.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/pr114130.c: New.

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
(cherry picked from commit fd07a29e39f5347d6cef3e7042a32306f97a1719)

diff --git a/gcc/config/riscv/sync.md b/gcc/config/riscv/sync.md
index 9fc626267de3840ce15d196bff72440a980fd234..9fbd89d7cc8bddf9ae6a8401129d42730fca8d1e 100644 (file)
--- a/gcc/config/riscv/sync.md
+++ b/gcc/config/riscv/sync.md
@@ -383,6 +383,15 @@
    (match_operand:SI 7 "const_int_operand" "")] ;; mod_f
   "TARGET_ATOMIC"
 {
+  if (word_mode != <MODE>mode && operands[3] != const0_rtx)
+    {
+      /* We don't have SI mode compare on RV64, so we need to make sure expected
+        value is sign-extended.  */
+      rtx tmp0 = gen_reg_rtx (word_mode);
+      emit_insn (gen_extend_insn (tmp0, operands[3], word_mode, <MODE>mode, 0));
+      operands[3] = simplify_gen_subreg (<MODE>mode, tmp0, word_mode, 0);
+    }
+
   emit_insn (gen_atomic_cas_value_strong<mode> (operands[1], operands[2],
                                                operands[3], operands[4],
                                                operands[6], operands[7]));

diff --git a/gcc/testsuite/gcc.target/riscv/pr114130.c b/gcc/testsuite/gcc.target/riscv/pr114130.c
new file mode 100644 (file)
index 0000000..cd0a4e8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr114130.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc -mabi=lp64 -O" } */
+#include <stdint-gcc.h>
+
+void foo(uint32_t *p) {
+    uintptr_t x = *(uintptr_t *)p;
+    uint32_t e = !p ? 0 : (uintptr_t)p >> 1;
+    uint32_t d = (uintptr_t)x;
+    __atomic_compare_exchange(p, &e, &d, 0, __ATOMIC_RELAXED, __ATOMIC_RELAXED);
+}
+
+/* { dg-final { scan-assembler-times "sext.w\t" 1 } } */