[X86] Generate testl instruction through truncates.
Summary:
This was introduced in D42646 but ended up being reverted because the original implementation was buggy.
Depends on D42646
Reviewers: craig.topper, niravd, spatel, hfinkel
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D42741
llvm-svn: 323899
diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index da53d33..9e7de71 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -3052,70 +3052,55 @@
if (!C) break;
uint64_t Mask = C->getZExtValue();
- // For example, convert "testl %eax, $8" to "testb %al, $8"
+ MVT VT;
+ int SubRegOp;
+ unsigned Op;
+
if (isUInt<8>(Mask) &&
(!(Mask & 0x80) || hasNoSignedComparisonUses(Node))) {
- SDValue Imm = CurDAG->getTargetConstant(Mask, dl, MVT::i8);
- SDValue Reg = N0.getOperand(0);
-
- // Extract the l-register.
- SDValue Subreg = CurDAG->getTargetExtractSubreg(X86::sub_8bit, dl,
- MVT::i8, Reg);
-
- // Emit a testb.
- SDNode *NewNode = CurDAG->getMachineNode(X86::TEST8ri, dl, MVT::i32,
- Subreg, Imm);
- // Replace SUB|CMP with TEST, since SUB has two outputs while TEST has
- // one, do not call ReplaceAllUsesWith.
- ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
- SDValue(NewNode, 0));
- CurDAG->RemoveDeadNode(Node);
- return;
+ // For example, convert "testl %eax, $8" to "testb %al, $8"
+ VT = MVT::i8;
+ SubRegOp = X86::sub_8bit;
+ Op = X86::TEST8ri;
+ } else if (OptForMinSize && isUInt<16>(Mask) &&
+ (!(Mask & 0x8000) || hasNoSignedComparisonUses(Node))) {
+ // For example, "testl %eax, $32776" to "testw %ax, $32776".
+ // NOTE: We only want to form TESTW instructions if optimizing for
+ // min size. Otherwise we only save one byte and possibly get a length
+ // changing prefix penalty in the decoders.
+ VT = MVT::i16;
+ SubRegOp = X86::sub_16bit;
+ Op = X86::TEST16ri;
+ } else if (isUInt<32>(Mask) && N0.getValueType() != MVT::i16 &&
+ (!(Mask & 0x80000000) || hasNoSignedComparisonUses(Node))) {
+ // For example, "testq %rax, $268468232" to "testl %eax, $268468232".
+ // NOTE: We only want to run that transform if N0 is 32 or 64 bits.
+ // Otherwize, we find ourselves in a position where we have to do
+ // promotion. If previous passes did not promote the and, we assume
+ // they had a good reason not to and do not promote here.
+ VT = MVT::i32;
+ SubRegOp = X86::sub_32bit;
+ Op = X86::TEST32ri;
+ } else {
+ // No eligible transformation was found.
+ break;
}
- // For example, "testl %eax, $32776" to "testw %ax, $32776".
- // NOTE: We only want to form TESTW instructions if optimizing for
- // min size. Otherwise we only save one byte and possibly get a length
- // changing prefix penalty in the decoders.
- if (OptForMinSize && isUInt<16>(Mask) && N0.getValueType() != MVT::i16 &&
- (!(Mask & 0x8000) || hasNoSignedComparisonUses(Node))) {
- SDValue Imm = CurDAG->getTargetConstant(Mask, dl, MVT::i16);
- SDValue Reg = N0.getOperand(0);
+ SDValue Imm = CurDAG->getTargetConstant(Mask, dl, VT);
+ SDValue Reg = N0.getOperand(0);
- // Extract the 16-bit subregister.
- SDValue Subreg = CurDAG->getTargetExtractSubreg(X86::sub_16bit, dl,
- MVT::i16, Reg);
+ // Extract the subregister if necessary.
+ if (N0.getValueType() != VT)
+ Reg = CurDAG->getTargetExtractSubreg(SubRegOp, dl, VT, Reg);
- // Emit a testw.
- SDNode *NewNode = CurDAG->getMachineNode(X86::TEST16ri, dl, MVT::i32,
- Subreg, Imm);
- // Replace SUB|CMP with TEST, since SUB has two outputs while TEST has
- // one, do not call ReplaceAllUsesWith.
- ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
- SDValue(NewNode, 0));
- CurDAG->RemoveDeadNode(Node);
- return;
- }
-
- // For example, "testq %rax, $268468232" to "testl %eax, $268468232".
- if (isUInt<32>(Mask) && N0.getValueType() == MVT::i64 &&
- (!(Mask & 0x80000000) || hasNoSignedComparisonUses(Node))) {
- SDValue Imm = CurDAG->getTargetConstant(Mask, dl, MVT::i32);
- SDValue Reg = N0.getOperand(0);
-
- // Extract the 32-bit subregister.
- SDValue Subreg = CurDAG->getTargetExtractSubreg(X86::sub_32bit, dl,
- MVT::i32, Reg);
- // Emit a testl.
- SDNode *NewNode = CurDAG->getMachineNode(X86::TEST32ri, dl, MVT::i32,
- Subreg, Imm);
- // Replace SUB|CMP with TEST, since SUB has two outputs while TEST has
- // one, do not call ReplaceAllUsesWith.
- ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
- SDValue(NewNode, 0));
- CurDAG->RemoveDeadNode(Node);
- return;
- }
+ // Emit a testl or testw.
+ SDNode *NewNode = CurDAG->getMachineNode(Op, dl, MVT::i32, Reg, Imm);
+ // Replace SUB|CMP with TEST, since SUB has two outputs while TEST has
+ // one, do not call ReplaceAllUsesWith.
+ ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
+ SDValue(NewNode, 0));
+ CurDAG->RemoveDeadNode(Node);
+ return;
}
break;
}