[PATCH v2] RISC-V: Correct the mode that is causing the program to fail for XTheadCondMov

Jin Ma jinma@linux.alibaba.com
Mon Jan 20 05:56:10 GMT 2025


For XTheadCondMov, the bit width of rs2 should always be XLEN-sized, otherwise
the program logic will be wrong.

Reference form
https://github.com/XUANTIE-RV/thead-extension-spec/releases/download/2.3.0/xthead-2023-11-10-2.3.0.pdf

Synopsis
Move if equal zero.

Mnemonic
th.mveqz rd, rs1, rs2

Description
This instruction moves the content of register rs1 into rd if the content of rs2 is 0x0.
Otherwise, the value of rd does not change.

Operation
if (reg[rs2] == 0x0)
  reg[rd] := reg[rs1]

gcc/ChangeLog:

	* config/riscv/thead.md (*th_cond_mov<GPR:mode><GPR2:mode>):
	Change GPR2 to X.
	(*th_cond_mov<GPR:mode>): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/xtheadcondmov-bug.c: New test.
---
 gcc/config/riscv/thead.md                          |  4 ++--
 gcc/testsuite/gcc.target/riscv/xtheadcondmov-bug.c | 12 ++++++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/riscv/xtheadcondmov-bug.c

diff --git a/gcc/config/riscv/thead.md b/gcc/config/riscv/thead.md
index 54b9737b4308..d816f3b86dde 100644
--- a/gcc/config/riscv/thead.md
+++ b/gcc/config/riscv/thead.md
@@ -154,11 +154,11 @@ (define_insn "*th_tst<mode>3"
 
 ;; XTheadCondMov
 
-(define_insn "*th_cond_mov<GPR:mode><GPR2:mode>"
+(define_insn "*th_cond_mov<GPR:mode>"
   [(set (match_operand:GPR 0 "register_operand" "=r,r")
 	(if_then_else:GPR
 	 (match_operator 4 "equality_operator"
-		[(match_operand:GPR2 1 "register_operand" "r,r")
+		[(match_operand:X 1 "register_operand" "r,r")
 		 (const_int 0)])
 	 (match_operand:GPR 2 "reg_or_0_operand" "rJ,0")
 	 (match_operand:GPR 3 "reg_or_0_operand" "0,rJ")))]
diff --git a/gcc/testsuite/gcc.target/riscv/xtheadcondmov-bug.c b/gcc/testsuite/gcc.target/riscv/xtheadcondmov-bug.c
new file mode 100644
index 000000000000..01cec6292919
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/xtheadcondmov-bug.c
@@ -0,0 +1,12 @@
+/* { dg-do compile  { target { rv64 } } } */
+/* { dg-options "-march=rv64gc_xtheadcondmov -mabi=lp64d -O2" } */
+
+long long int
+foo (long long int x, long long int y)
+{
+  if (((int) x | (int) y) != 0)
+    return 6;
+  return x + y;
+}
+
+/* { dg-final { scan-assembler-times {\msext\.w\M} 1 } } */
-- 
2.25.1



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