https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125478
Bug ID: 125478
Summary: [16/17 Regression][RISCV][Miscompile] GCC -
miscompiles at -O3 since
g:948d33f490a6b0051376da6bdcf55223a552b30f
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: skothadiya at whileone dot in
Target Milestone: ---
Created attachment 64565
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64565&action=edit
Attached reduced testcase
Description:
The testcase code involves for loops on various datatypes, compiles correctly
on x86_64 and produces the expected output. However, when compiled for the
riscv64 architecture, the resulting binary yields an incorrect value. The
expected output is 0, but the program returns 18446744073709551615. This
miscompilation occurs with optimization enabled at level -O3.
COMMANDS:
/riscv-gnu-toolchain-build/bin/riscv64-unknown-linux-gnu-gcc -march=rv64gcv -O3
-mrvv-vector-bits=zvl red.c -o user-config.out -fsigned-char
-fno-strict-aliasing -fwrapv -Wno-unknown-warning-option -Werror -Wfatal-errors
-Wall -Wformat -Wno-int-in-bool-context -Wno-dangling-pointer
-Wno-compare-distinct-pointer-types -Wno-overflow -Wuninitialized
-Warray-bounds -Wreturn-type -Wno-unused-function -Wno-unused-variable
-Wno-unused-but-set-variable -Wno-unused-value -Wno-address -Wno-bool-compare
-Wno-pointer-sign -Wno-bool-operation -Wno-tautological-compare
-Wno-self-assign -Wno-implicit-const-int-float-conversion
-Wno-constant-conversion -Wno-unused-value
-Wno-tautological-constant-out-of-range-compare -Wno-constant-logical-operand
-Wno-parentheses-equality -Wno-pointer-sign
QEMU_CPU=rv64,vlen=128,rvv_ta_all_1s=true,rvv_ma_all_1s=true,v=true,vext_spec=v1.0,zve32f=true,zve64f=true
timeout --verbose -k 0.1 4 /riscv-gnu-toolchain-build/bin/qemu-riscv64
user-config.out 1
18446744073709551615
//Expected Output: 0
//Actual Output: 18446744073709551615
-- testcase (red.c) --
long long a;
long b;
char c[169];
int d;
int printf(const char *, ...);
int main() {
for (long g=0; g<13; ++g)
for (long h=0; h<13; ++h)
c[g*13 +h] = 8;
for (unsigned g=0; g<13; g++)
for (int h=0; h<13; h +=3)
b += (c[g*13+h]) >> c[g*13 +9];
a = (int)b;
printf("%llu\n", a);
}
The issue is Found via fuzzer.
