From f64e48dbee1a4ab0b786294ce734d99193b296e4 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Tue, 3 Jul 2018 05:05:54 -0400 Subject: [PATCH] target/arm: Fix SVE signed division vs x86 overflow exception We already check for the same condition within the normal integer sdiv and sdiv64 helpers. Use a slightly different formation that does not require deducing the expression type. Backports commit 7e8fafbfd0537937ba8fb366a90ea6548cc31576 from qemu --- qemu/target/arm/sve_helper.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/qemu/target/arm/sve_helper.c b/qemu/target/arm/sve_helper.c index b98cf6a7..93c0dd08 100644 --- a/qemu/target/arm/sve_helper.c +++ b/qemu/target/arm/sve_helper.c @@ -368,7 +368,15 @@ void HELPER(NAME)(void *vd, void *vn, void *vm, void *vg, uint32_t desc) \ #define DO_MIN(N, M) ((N) >= (M) ? (M) : (N)) #define DO_ABD(N, M) ((N) >= (M) ? (N) - (M) : (M) - (N)) #define DO_MUL(N, M) (N * M) -#define DO_DIV(N, M) (M ? N / M : 0) +/* + * We must avoid the C undefined behaviour cases: division by + * zero and signed division of INT_MIN by -1. Both of these + * have architecturally defined required results for Arm. + * We special case all signed divisions by -1 to avoid having + * to deduce the minimum integer for the type involved. + */ +#define DO_SDIV(N, M) (unlikely(M == 0) ? 0 : unlikely(M == -1) ? -N : N / M) +#define DO_UDIV(N, M) (unlikely(M == 0) ? 0 : N / M) DO_ZPZZ(sve_and_zpzz_b, uint8_t, H1, DO_AND) DO_ZPZZ(sve_and_zpzz_h, uint16_t, H1_2, DO_AND) @@ -476,11 +484,11 @@ DO_ZPZZ(sve_umulh_zpzz_h, uint16_t, H1_2, do_mulh_h) DO_ZPZZ(sve_umulh_zpzz_s, uint32_t, H1_4, do_mulh_s) DO_ZPZZ_D(sve_umulh_zpzz_d, uint64_t, do_umulh_d) -DO_ZPZZ(sve_sdiv_zpzz_s, int32_t, H1_4, DO_DIV) -DO_ZPZZ_D(sve_sdiv_zpzz_d, int64_t, DO_DIV) +DO_ZPZZ(sve_sdiv_zpzz_s, int32_t, H1_4, DO_SDIV) +DO_ZPZZ_D(sve_sdiv_zpzz_d, int64_t, DO_SDIV) -DO_ZPZZ(sve_udiv_zpzz_s, uint32_t, H1_4, DO_DIV) -DO_ZPZZ_D(sve_udiv_zpzz_d, uint64_t, DO_DIV) +DO_ZPZZ(sve_udiv_zpzz_s, uint32_t, H1_4, DO_UDIV) +DO_ZPZZ_D(sve_udiv_zpzz_d, uint64_t, DO_UDIV) /* Note that all bits of the shift are significant and not modulo the element size. */