[PATCH v2] RISC-V: Fix Zicond ICE on large constants

[Tsukasa OI <research_trasio@irq.a4lg.com>]

From: Tsukasa OI <research_trasio@irq.a4lg.com>

Large constant cons and/or alt will trigger ICEs building GCC target
libraries (libgomp and libatomic) when the 'Zicond' extension is enabled.

For instance, zicond-ice-2.c (new test case in this commit) will cause
an ICE when SOME_NUMBER is 0x1000 or larger.  While opposite numbers
corresponding cons/alt (two temp2 variables) are checked, cons/alt
themselves are not checked and causing 2 ICEs building
GCC target libraries as of this writing:

1.  gcc/libatomic/config/posix/lock.c
2.  gcc/libgomp/fortran.c

Coercing a large value into a register will fix the issue.

It also coerce a large cons into a register on "imm, imm" case (the author
could not reproduce but possible to cause an ICE).

gcc/ChangeLog:

	* config/riscv/riscv.cc (riscv_expand_conditional_move): Force
	large constant cons/alt into a register.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/zicond-ice-2.c: New test.  This is based on
	an ICE at libat_lock_n func on gcc/libatomic/config/posix/lock.c
	but heavily minimized.
---
 gcc/config/riscv/riscv.cc                     | 21 +++++++++++++------
 gcc/testsuite/gcc.target/riscv/zicond-ice-2.c | 11 ++++++++++
 2 files changed, 26 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/riscv/zicond-ice-2.c

diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 8d8f7b4f16ed..e306d57814be 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -3917,6 +3917,11 @@ riscv_expand_conditional_move (rtx dest, rtx op, rtx cons, rtx alt)
 				  gen_rtx_IF_THEN_ELSE (mode, cond,
 							CONST0_RTX (mode),
 							alt)));
+	  /* CONS might not fit into a signed 12 bit immediate suitable
+	     for an addi instruction.  If that's the case, force it
+	     into a register.  */
+	  if (!SMALL_OPERAND (INTVAL (cons)))
+	    cons = force_reg (mode, cons);
 	  riscv_emit_binary (PLUS, dest, dest, cons);
 	  return true;
 	}
@@ -3940,11 +3945,13 @@ riscv_expand_conditional_move (rtx dest, rtx op, rtx cons, rtx alt)
 	  rtx temp1 = gen_reg_rtx (mode);
 	  rtx temp2 = gen_int_mode (-1 * INTVAL (cons), mode);
 
-	  /* TEMP2 might not fit into a signed 12 bit immediate suitable
-	     for an addi instruction.  If that's the case, force it into
-	     a register.  */
+	  /* TEMP2 and/or CONS might not fit into a signed 12 bit immediate
+	     suitable for an addi instruction.  If that's the case, force it
+	     into a register.  */
 	  if (!SMALL_OPERAND (INTVAL (temp2)))
 	    temp2 = force_reg (mode, temp2);
+	  if (!SMALL_OPERAND (INTVAL (cons)))
+	    cons = force_reg (mode, cons);
 
 	  riscv_emit_binary (PLUS, temp1, alt, temp2);
 	  emit_insn (gen_rtx_SET (dest,
@@ -3986,11 +3993,13 @@ riscv_expand_conditional_move (rtx dest, rtx op, rtx cons, rtx alt)
 	  rtx temp1 = gen_reg_rtx (mode);
 	  rtx temp2 = gen_int_mode (-1 * INTVAL (alt), mode);
 
-	  /* TEMP2 might not fit into a signed 12 bit immediate suitable
-	     for an addi instruction.  If that's the case, force it into
-	     a register.  */
+	  /* TEMP2 and/or ALT might not fit into a signed 12 bit immediate
+	     suitable for an addi instruction.  If that's the case, force it
+	     into a register.  */
 	  if (!SMALL_OPERAND (INTVAL (temp2)))
 	    temp2 = force_reg (mode, temp2);
+	  if (!SMALL_OPERAND (INTVAL (alt)))
+	    alt = force_reg (mode, alt);
 
 	  riscv_emit_binary (PLUS, temp1, cons, temp2);
 	  emit_insn (gen_rtx_SET (dest,
diff --git a/gcc/testsuite/gcc.target/riscv/zicond-ice-2.c b/gcc/testsuite/gcc.target/riscv/zicond-ice-2.c
new file mode 100644
index 000000000000..ffd8dcb5814e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zicond-ice-2.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc_zicond -mabi=lp64d" { target { rv64 } } } */
+/* { dg-options "-march=rv32gc_zicond -mabi=ilp32d" { target { rv32 } } } */
+
+#define SOME_NUMBER 0x1000
+
+unsigned long
+d (unsigned long n)
+{
+  return n > SOME_NUMBER ? SOME_NUMBER : n;
+}

base-commit: 72b639760a891c406725854bfb08132c83f0761a
-- 
2.42.0