Currently the following RTL for zero extension
| (insn 8 7 9 (set (reg:DI 0 %r0 [25])
| (zero_extend:DI (reg:SI 0 %r0 [24]))) {zero_extendsidi2}
| (nil))
generates
| r0 = r0
which is just a 64-bit copy and doesn't clear the upper 32-bits as
semantically required by the pattern.
The issue is pattern's asm template missing ‘w’/'W' causing bpf_print_register
()
to only emit 'r' regs. Using ‘W’ in template generates correct code.
| w0 = w0
Note that 'W specifier ignores the RTL mode and unconditionally emits
the 'w' reg which might feel like creating a potential future bug.
However for this insn, it is correct/completely safe as follows:
- 'W1' for src operand: src operand has a SI mode in pattern.
- 'W0' for dst: Technically dst is DI, but the upper 32-bits of output
have to be 0 due to zero-extension, thus a 'w' reg is OK.
For selftests this is a wash, except for some spurious changes.
PR target/124670
gcc/ChangeLog:
* config/bpf/bpf.md (zero_extendsidi2): Use 'W' in asm template.
gcc/testsuite/ChangeLog:
* gcc.target/bpf/zero-ext.c: New test.
Signed-off-by: Vineet Gupta <[email protected]>
---
Changes since v1
- src operand also changed to 'W'
---
gcc/config/bpf/bpf.md | 2 +-
gcc/testsuite/gcc.target/bpf/zero-ext.c | 11 +++++++++++
2 files changed, 12 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.target/bpf/zero-ext.c
diff --git a/gcc/config/bpf/bpf.md b/gcc/config/bpf/bpf.md
index bc739f2746c0..c2c3152b5d7c 100644
--- a/gcc/config/bpf/bpf.md
+++ b/gcc/config/bpf/bpf.md
@@ -300,7 +300,7 @@
(match_operand:SI 1 "nonimmediate_operand" "r,q")))]
""
"@
- *return bpf_output_move (operands, bpf_has_alu32 ? \"{mov32\t%0,%1|%0 =
%1}\" : \"{mov\t%0,%1\;and\t%0,0xffffffff|%0 = %1;%0 &= 0xffffffff}\");
+ *return bpf_output_move (operands, bpf_has_alu32 ? \"{mov32\t%0,%1|%W0 =
%W1}\" : \"{mov\t%0,%1\;and\t%0,0xffffffff|%0 = %1;%0 &= 0xffffffff}\");
*return bpf_output_move (operands, \"{ldxw\t%0,%1|%0 = *(u32 *) %1}\");"
[(set_attr "type" "alu,ldx")])
diff --git a/gcc/testsuite/gcc.target/bpf/zero-ext.c
b/gcc/testsuite/gcc.target/bpf/zero-ext.c
new file mode 100644
index 000000000000..a57c7dc521f0
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/zero-ext.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mcpu=v4" } */
+
+int bar_int(void);
+
+int foo_int(void) {
+ if (bar_int() != 1) return 0; else return 1;
+}
+
+/* { dg-final { scan-assembler-not {r0 = r0} } } */
+/* { dg-final { scan-assembler-times {w0 = w0} 1 } } */
--
2.53.0
