[RISC-V][PR target/116240] Ensure object is a comparison before extracting arguments

This was supposed to go out the door yesterday, but I kept getting interrupted.

The target bits for rtx costing can't assume the rtl they're given actually
matches a target pattern.   It's just kind of inherent in how the costing
routines get called in various places.

In this particular case we're trying to cost a conditional move:

(set (dest) (if_then_else (cond) (true) (false))

On the RISC-V port the backend only allows actual conditionals for COND.  So
something like (eq (reg) (const_int 0)).  In the costing code for if-then-else
we did something like

(XEXP (XEXP (cond, 0), 0)))

Which fails miserably if COND is a terminal node like (reg) rather than (ne
(reg) (const_int 0)

So this patch tightens up the RTL scanning to ensure that we have a comparison
before we start looking at the comparison's arguments.

Run through my tester without incident, but I'll wait for the pre-commit tester
to run through a cycle before pushing to the trunk.

Jeff

ps.   We probably could support a naked REG for the condition and internally convert it to (ne (reg) (const_int 0)), but I don't think it likely happens with any regularity.

	PR target/116240
gcc/
	* config/riscv/riscv.cc (riscv_rtx_costs): Ensure object is a
	comparison before looking at its arguments.

gcc/testsuite
	* gcc.target/riscv/pr116240.c: New test.

diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 3bc6a5e41ab8ce40ba118ed852cee5f256af8a31..16ed2d91663ed83c9d83093d7f2a5021ce14170c 100644 (file)
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -3286,9 +3286,11 @@ riscv_rtx_costs (rtx x, machine_mode mode, int outer_code, int opno ATTRIBUTE_UN
                    && XEXP (x, 2) == CONST0_RTX (GET_MODE (XEXP (x, 1))))
                   || (GET_CODE (XEXP (x, 2)) == REG
                       && XEXP (x, 1) == CONST0_RTX (GET_MODE (XEXP (x, 2))))
-                  || (GET_CODE (XEXP (x, 1)) == REG
+                  || (COMPARISON_P (XEXP (x, 0))
+                      && GET_CODE (XEXP (x, 1)) == REG
                       && rtx_equal_p (XEXP (x, 1), XEXP (XEXP (x, 0), 0)))
-                  || (GET_CODE (XEXP (x, 1)) == REG
+                  || (COMPARISON_P (XEXP (x, 0))
+                      && GET_CODE (XEXP (x, 1)) == REG
                       && rtx_equal_p (XEXP (x, 2), XEXP (XEXP (x, 0), 0)))))
        {
          *total = COSTS_N_INSNS (1);

diff --git a/gcc/testsuite/gcc.target/riscv/pr116240.c b/gcc/testsuite/gcc.target/riscv/pr116240.c
new file mode 100644 (file)
index 0000000..7e3eaa2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr116240.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-fwrapv -march=rv64imvxtheadcondmov_xventanacondops -mabi=lp64d" } */
+
+int a, b;
+void c() {
+  int e = a >= 2 ? b : a;
+  short d = e * 2;
+  if (d)
+    for (;;)
+      ;
+}
+