diff options
Diffstat (limited to 'lib/Target/ARM/ARMInstrInfo.td')
| -rw-r--r-- | lib/Target/ARM/ARMInstrInfo.td | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/lib/Target/ARM/ARMInstrInfo.td b/lib/Target/ARM/ARMInstrInfo.td index 59a222c..51fc152 100644 --- a/lib/Target/ARM/ARMInstrInfo.td +++ b/lib/Target/ARM/ARMInstrInfo.td @@ -1694,13 +1694,19 @@ def RSCSrs : AXI1<0b0111, (outs GPR:$dst), (ins GPR:$a, so_reg:$b), } // (sub X, imm) gets canonicalized to (add X, -imm). Match this form. +// The assume-no-carry-in form uses the negation of the input since add/sub +// assume opposite meanings of the carry flag (i.e., carry == !borrow). +// See the definition of AddWithCarry() in the ARM ARM A2.2.1 for the gory +// details. def : ARMPat<(add GPR:$src, so_imm_neg:$imm), (SUBri GPR:$src, so_imm_neg:$imm)>; - -//def : ARMPat<(addc GPR:$src, so_imm_neg:$imm), -// (SUBSri GPR:$src, so_imm_neg:$imm)>; -//def : ARMPat<(adde GPR:$src, so_imm_neg:$imm), -// (SBCri GPR:$src, so_imm_neg:$imm)>; +def : ARMPat<(addc GPR:$src, so_imm_neg:$imm), + (SUBSri GPR:$src, so_imm_neg:$imm)>; +// The with-carry-in form matches bitwise not instead of the negation. +// Effectively, the inverse interpretation of the carry flag already accounts +// for part of the negation. +def : ARMPat<(adde GPR:$src, so_imm_not:$imm), + (SBCri GPR:$src, so_imm_not:$imm)>; // Note: These are implemented in C++ code, because they have to generate // ADD/SUBrs instructions, which use a complex pattern that a xform function |