Improve 64-subtraction of immediates when parts of the immediate can fit
in the literal field of an instruction. E.g.,
long long foo(long long a) {
return a - 734439407618LL;
}
rdar://7038284
llvm-svn: 108339
diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index 59a222c..51fc152 100644
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -1694,13 +1694,19 @@
}
// (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
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb2.td b/llvm/lib/Target/ARM/ARMInstrThumb2.td
index 11413de..bbe675e 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb2.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb2.td
@@ -122,6 +122,10 @@
return (uint32_t)(-N->getZExtValue()) < 255;
}], imm_neg_XFORM>;
+def imm0_255_not : PatLeaf<(i32 imm), [{
+ return (uint32_t)(~N->getZExtValue()) < 255;
+}], imm_comp_XFORM>;
+
// Define Thumb2 specific addressing modes.
// t2addrmode_imm12 := reg + imm12
@@ -1391,13 +1395,32 @@
BinOpFrag<(subc node:$LHS, node:$RHS)>>;
// (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.
+// The AddedComplexity preferences the first variant over the others since
+// it can be shrunk to a 16-bit wide encoding, while the others cannot.
let AddedComplexity = 1 in
-def : T2Pat<(add GPR:$src, imm0_255_neg:$imm),
- (t2SUBri GPR:$src, imm0_255_neg:$imm)>;
-def : T2Pat<(add GPR:$src, t2_so_imm_neg:$imm),
- (t2SUBri GPR:$src, t2_so_imm_neg:$imm)>;
-def : T2Pat<(add GPR:$src, imm0_4095_neg:$imm),
- (t2SUBri12 GPR:$src, imm0_4095_neg:$imm)>;
+def : T2Pat<(add GPR:$src, imm0_255_neg:$imm),
+ (t2SUBri GPR:$src, imm0_255_neg:$imm)>;
+def : T2Pat<(add GPR:$src, t2_so_imm_neg:$imm),
+ (t2SUBri GPR:$src, t2_so_imm_neg:$imm)>;
+def : T2Pat<(add GPR:$src, imm0_4095_neg:$imm),
+ (t2SUBri12 GPR:$src, imm0_4095_neg:$imm)>;
+let AddedComplexity = 1 in
+def : T2Pat<(addc GPR:$src, imm0_255_neg:$imm),
+ (t2SUBSri GPR:$src, imm0_255_neg:$imm)>;
+def : T2Pat<(addc GPR:$src, t2_so_imm_neg:$imm),
+ (t2SUBSri GPR:$src, t2_so_imm_neg:$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.
+let AddedComplexity = 1 in
+def : T2Pat<(adde GPR:$src, imm0_255_not:$imm),
+ (t2SBCSri GPR:$src, imm0_255_not:$imm)>;
+def : T2Pat<(adde GPR:$src, t2_so_imm_not:$imm),
+ (t2SBCSri GPR:$src, t2_so_imm_not:$imm)>;
// Select Bytes -- for disassembly only