# *****************************************************************
#
#               The Compcert verified compiler
#
#           Xavier Leroy, INRIA Paris
#
# Copyright (c) 2016 Institut National de Recherche en Informatique et
#  en Automatique.
#
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# Helper functions for 64-bit integer arithmetic.  PowerPC version.

        .text

### Signed multiply-high

# Hacker's Delight section 8.3:
# - compute high 64 bits of the unsigned product X * Y  (see i64_umulh.S)
# - subtract X if Y < 0
# - subtract Y if X < 0

        .balign 16
        .globl __compcert_i64_smulh
__compcert_i64_smulh:
# r7:r8:r9 accumulate bits 127:32 of the full unsigned product
        mulhwu  r9, r4, r6        # r9 = high half of XL.YL
        mullw   r0, r4, r5        # r0 = low half of XL.YH
        addc    r9, r9, r0
        mulhwu  r0, r4, r5        # r0 = high half of XL.YH
        addze   r8, r0
        mullw   r0, r3, r6        # r0 = low half of XH.YL
        addc    r9, r9, r0
        mulhwu  r0, r3, r6        # r0 = high half of XH.YL
        adde    r8, r8, r0
        li      r7, 0
        addze   r7, r7
        mullw   r0, r3, r5        # r0 = low half of XH.YH
        addc    r8, r8, r0
        mulhwu  r0, r3, r5        # r0 = high half of XH.YH
        adde    r7, r7, r0
# Here r7:r8 contains the high 64 bits of the unsigned product.
# Now, test signs and subtract if needed
        srawi   r0, r3, 31        # r0 = -1 if X < 0, r0 = 0 if X >= 0
        srawi   r9, r5, 31        # r9 = -1 if Y < 0, r9 = 0 if Y >= 0
        and     r3, r3, r9        # set X = 0 if Y >= 0
        and     r4, r4, r9
        and     r5, r5, r0        # set Y = 0 if X >= 0
        and     r6, r6, r0
        subfc   r8, r4, r8        # subtract X
        subfe   r7, r3, r7
        subfc   r4, r6, r8        # subtract Y
        subfe   r3, r5, r7
        blr
        .type __compcert_i64_smulh, @function
        .size __compcert_i64_smulh, .-__compcert_i64_smulh