From d10c0dce53b2f1435fb66a570f15310baef5172d Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Sat, 10 Feb 2024 12:52:23 +0100
Subject: [PATCH] lower-bitint: Fix up .{ADD,SUB}_OVERFLOW lowering
torture/bitint-37.c test FAILed on i686-linux e.g. on
signed _BitInt(575) + unsigned _BitInt(575) -> signed _BitInt(575)
__builtin_add_overflow. With 64-bit limbs, we use 4 .UADDC calls in
the IL, 2 in a loop (which handles the first 8 limbs), then one partial
limb (we use 63 bits from that) and finally last_ovf case due to the
mixing of signed vs. unsigned.
But with 32-bit limbs, we use 5 .UADDC calls in the IL, 2 in a loop (which
handles the first 16 limbs), then one full limb above that, one partial
(31 bits) and finally last_ovf case, and for the last_ovf case the code
computed incorrect idx and so partly did the wrong thing, e.g. overwrote
the result from the previous .UADDC.
Fixed thusly.
2024-02-10 Jakub Jelinek <jakub@redhat.com>
* gimple-lower-bitint.cc (itint_large_huge::lower_addsub_overflow): Fix
computation of idx for i == 4 of bitint_prec_huge.
---
gcc/gimple-lower-bitint.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc
index e29d83193265..caa33e0aacf1 100644
--- a/gcc/gimple-lower-bitint.cc
+++ b/gcc/gimple-lower-bitint.cc
@@ -4031,7 +4031,7 @@ bitint_large_huge::lower_addsub_overflow (tree obj, gimple *stmt)
if (kind != bitint_prec_huge)
idx = size_int (i);
else if (i >= 2)
- idx = size_int (fin + (i > 2));
+ idx = size_int (fin + i - 2);
if (!last_ovf || i < cnt - 1)
{
if (type0 != TREE_TYPE (arg0))
--
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