From: Bin Cheng Date: Wed, 28 Jul 2021 09:50:59 +0000 (+0800) Subject: AArch64: use stable sorting in generating ldp/stp X-Git-Tag: basepoints/gcc-13~5754 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b662250c1f5e0e453f1fd6022cc47e517f70fa8e;p=thirdparty%2Fgcc.git AArch64: use stable sorting in generating ldp/stp In some corner cases, we have code as below: [base + 0x310] = A [base + 0x320] = B [base + 0x330] = C [base + 0x320] = D unstable sorting could result in wrong value in offset 0x320. The patch fixes it by using gcc_stablesort. 2021-07-28 Bin Cheng * config/aarch64/aarch64.c (aarch64_gen_adjusted_ldpstp): use gcc_stablesort. --- diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c index 3bdf19d71b54..e2114605901b 100644 --- a/gcc/config/aarch64/aarch64.c +++ b/gcc/config/aarch64/aarch64.c @@ -24441,8 +24441,16 @@ aarch64_gen_adjusted_ldpstp (rtx *operands, bool load, for (int i = 0; i < 8; i ++) temp_operands[i] = operands[i]; - /* Sort the operands. */ - qsort (temp_operands, 4, 2 * sizeof (rtx *), aarch64_ldrstr_offset_compare); + /* Sort the operands. Note for cases as below: + [base + 0x310] = A + [base + 0x320] = B + [base + 0x330] = C + [base + 0x320] = D + We need stable sorting otherwise wrong data may be store to offset 0x320. + Also note the dead store in above case should be optimized away, but no + guarantees here. */ + gcc_stablesort(temp_operands, 4, 2 * sizeof (rtx *), + aarch64_ldrstr_offset_compare); /* Copy the memory operands so that if we have to bail for some reason the original addresses are unchanged. */