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[RISC-V][PR target/120674] Avoid division by zero in dwarf emitter when vector is not enabled

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This is a RISC-V specific failure in the dwarf2 emitter.  When vector is not
enabled riscv_convert_vector_chunks sets the riscv_vector_chunks poly_int to
[1, 0].

riscv_dwarf_poly_indeterminite_value pulls out that 0 coefficient and uses that
as FACTOR triggering a divide by zero here:

>               /* Add COEFF * ((REGNO / FACTOR) - BIAS) to the value:
>                  add COEFF * (REGNO / FACTOR) now and subtract
>                  COEFF * BIAS from the final constant part.  */
>               constant -= coeff * bias;
>               add_loc_descr (&ret, new_reg_loc_descr (regno, 0));
>               if (coeff % factor == 0)
>                 coeff /= factor;
>               else
>                 {
>                   int amount = exact_log2 (factor);
>                   gcc_assert (amount >= 0);
>                   add_loc_descr (&ret, int_loc_descriptor (amount));
>                   add_loc_descr (&ret, new_loc_descr (DW_OP_shr, 0, 0));
>                 }

Per Robin's recommendation this patch adjusts
riscv_dwarf_poly_indeterminite_value to never set FACTOR to 0, but instead
detect this case and adjust its value to 1.

That fixes the ICE and looks good across the board in my tester. Waiting on
pre-commit CI, of course.

	PR target/120674
gcc/
	* config/riscv/riscv.cc (riscv_dwarf_poly_indeterminite_value): Do not
	set FACTOR to zero, for that case use one instead.

gcc/testsuite

	* gcc.target/riscv/pr120674.c: New test.
This commit is contained in:
Jeff Law
2025-10-13 14:33:10 -06:00
parent fcd30bdb83
commit a92369a6be
2 changed files with 13 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
gcc/config/riscv/riscv.cc
View File

@@ -12641,6 +12641,13 @@ riscv_dwarf_poly_indeterminate_value (unsigned int i, unsigned int *factor,
*/
gcc_assert (i == 1);
*factor = BYTES_PER_RISCV_VECTOR.coeffs[1];
/* The factor will be zero if vector is not enabled. That ultimately
causes problems in the dwarf2 emitter as the factor is used for
a division, causing a divide by zero. */
if (*factor == 0)
*factor = 1;
*offset = 1;
return RISCV_DWARF_VLENB;
}

6
gcc/testsuite/gcc.target/riscv/pr120674.c Normal file
View File

@@ -0,0 +1,6 @@
/* { dg-do compile } */
/* { dg-additional-options "-g -w -march=rv32gcv -mabi=ilp32" { target rv32 } } */
/* { dg-additional-options "-g -w -march=rv64gcv -mabi=lp64d" { target rv64 } } */
#pragma riscv intrinsic "vector"
void GB_AxB_saxpy5_unrolled_rvv() { vfloat64m8_t vc; }