[Bug target/123626] New: [16 Regression] [RISCV] [Miscompile] GCC - riscv64 target, miscompiles at -O3 as well as -O2 since g:08ccc67ef44b4ddea72ea50d465d38b87414ecce

[skothadiya at whileone dot in via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123626

            Bug ID: 123626
           Summary: [16 Regression] [RISCV] [Miscompile] GCC - riscv64
                    target, miscompiles at -O3 as well as -O2 since
                    g:08ccc67ef44b4ddea72ea50d465d38b87414ecce
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: skothadiya at whileone dot in
  Target Milestone: ---

Created attachment 63357
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=63357&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 180, but the program returns 200. This miscompilation occurs
with optimization enabled at level -O3 & -O2.


COMMANDS:
/riscv-gnu-toolchain-build/bin/riscv64-unknown-linux-gnu-gcc
-march=rv64gcv_zvl256b -O3 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=256,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
0
  //Expected Output: 180
  //Actual Output: 200


-- testcase (red.c) --

int printf(const char *, ...);
short a;
long long b;
char c[3][3][17];
_Bool d;

int main() {
  for (long g=0; g<3; ++g)
    for (long h=0; h<3; ++h)
      for (long i=0; i<17; ++i)
        c[g][h][i] = 2;

  for (char g=0; g<3; g-=13)
    for (short j=3; j<d+21; j+=2)
      a += 2;

  b = (int)a;
  printf("%llu\n", b);
}


The issue is Found via fuzzer.