Fix the x86 test-shrink optimization so that it doesn't shrink comparisons
when one of the bits being tested would end up being the sign bit in the
narrower type, and a signed comparison is being performed, since this would
change the result of the signed comparison. This fixes PR5132.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83670 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index 71b4062..5b678fb 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1625,6 +1625,68 @@
}
}
+/// HasNoSignedComparisonUses - Test whether the given X86ISD::CMP node has
+/// any uses which require the SF or OF bits to be accurate.
+static bool HasNoSignedComparisonUses(SDNode *N) {
+ // Examine each user of the node.
+ for (SDNode::use_iterator UI = N->use_begin(),
+ UE = N->use_end(); UI != UE; ++UI) {
+ // Only examine CopyToReg uses.
+ if (UI->getOpcode() != ISD::CopyToReg)
+ return false;
+ // Only examine CopyToReg uses that copy to EFLAGS.
+ if (cast<RegisterSDNode>(UI->getOperand(1))->getReg() !=
+ X86::EFLAGS)
+ return false;
+ // Examine each user of the CopyToReg use.
+ for (SDNode::use_iterator FlagUI = UI->use_begin(),
+ FlagUE = UI->use_end(); FlagUI != FlagUE; ++FlagUI) {
+ // Only examine the Flag result.
+ if (FlagUI.getUse().getResNo() != 1) continue;
+ // Anything unusual: assume conservatively.
+ if (!FlagUI->isMachineOpcode()) return false;
+ // Examine the opcode of the user.
+ switch (FlagUI->getMachineOpcode()) {
+ // These comparisons don't treat the most significant bit specially.
+ case X86::SETAr: case X86::SETAEr: case X86::SETBr: case X86::SETBEr:
+ case X86::SETEr: case X86::SETNEr: case X86::SETPr: case X86::SETNPr:
+ case X86::SETAm: case X86::SETAEm: case X86::SETBm: case X86::SETBEm:
+ case X86::SETEm: case X86::SETNEm: case X86::SETPm: case X86::SETNPm:
+ case X86::JA: case X86::JAE: case X86::JB: case X86::JBE:
+ case X86::JE: case X86::JNE: case X86::JP: case X86::JNP:
+ case X86::CMOVA16rr: case X86::CMOVA16rm:
+ case X86::CMOVA32rr: case X86::CMOVA32rm:
+ case X86::CMOVA64rr: case X86::CMOVA64rm:
+ case X86::CMOVAE16rr: case X86::CMOVAE16rm:
+ case X86::CMOVAE32rr: case X86::CMOVAE32rm:
+ case X86::CMOVAE64rr: case X86::CMOVAE64rm:
+ case X86::CMOVB16rr: case X86::CMOVB16rm:
+ case X86::CMOVB32rr: case X86::CMOVB32rm:
+ case X86::CMOVB64rr: case X86::CMOVB64rm:
+ case X86::CMOVBE16rr: case X86::CMOVBE16rm:
+ case X86::CMOVBE32rr: case X86::CMOVBE32rm:
+ case X86::CMOVBE64rr: case X86::CMOVBE64rm:
+ case X86::CMOVE16rr: case X86::CMOVE16rm:
+ case X86::CMOVE32rr: case X86::CMOVE32rm:
+ case X86::CMOVE64rr: case X86::CMOVE64rm:
+ case X86::CMOVNE16rr: case X86::CMOVNE16rm:
+ case X86::CMOVNE32rr: case X86::CMOVNE32rm:
+ case X86::CMOVNE64rr: case X86::CMOVNE64rm:
+ case X86::CMOVNP16rr: case X86::CMOVNP16rm:
+ case X86::CMOVNP32rr: case X86::CMOVNP32rm:
+ case X86::CMOVNP64rr: case X86::CMOVNP64rm:
+ case X86::CMOVP16rr: case X86::CMOVP16rm:
+ case X86::CMOVP32rr: case X86::CMOVP32rm:
+ case X86::CMOVP64rr: case X86::CMOVP64rm:
+ continue;
+ // Anything else: assume conservatively.
+ default: return false;
+ }
+ }
+ }
+ return true;
+}
+
SDNode *X86DAGToDAGISel::Select(SDValue N) {
SDNode *Node = N.getNode();
EVT NVT = Node->getValueType(0);
@@ -1978,7 +2040,9 @@
if (!C) break;
// For example, convert "testl %eax, $8" to "testb %al, $8"
- if ((C->getZExtValue() & ~UINT64_C(0xff)) == 0) {
+ if ((C->getZExtValue() & ~UINT64_C(0xff)) == 0 &&
+ (!(C->getZExtValue() & 0x80) ||
+ HasNoSignedComparisonUses(Node))) {
SDValue Imm = CurDAG->getTargetConstant(C->getZExtValue(), MVT::i8);
SDValue Reg = N0.getNode()->getOperand(0);
@@ -2004,7 +2068,9 @@
}
// For example, "testl %eax, $2048" to "testb %ah, $8".
- if ((C->getZExtValue() & ~UINT64_C(0xff00)) == 0) {
+ if ((C->getZExtValue() & ~UINT64_C(0xff00)) == 0 &&
+ (!(C->getZExtValue() & 0x8000) ||
+ HasNoSignedComparisonUses(Node))) {
// Shift the immediate right by 8 bits.
SDValue ShiftedImm = CurDAG->getTargetConstant(C->getZExtValue() >> 8,
MVT::i8);
@@ -2034,7 +2100,9 @@
// For example, "testl %eax, $32776" to "testw %ax, $32776".
if ((C->getZExtValue() & ~UINT64_C(0xffff)) == 0 &&
- N0.getValueType() != MVT::i16) {
+ N0.getValueType() != MVT::i16 &&
+ (!(C->getZExtValue() & 0x8000) ||
+ HasNoSignedComparisonUses(Node))) {
SDValue Imm = CurDAG->getTargetConstant(C->getZExtValue(), MVT::i16);
SDValue Reg = N0.getNode()->getOperand(0);
@@ -2048,7 +2116,9 @@
// For example, "testq %rax, $268468232" to "testl %eax, $268468232".
if ((C->getZExtValue() & ~UINT64_C(0xffffffff)) == 0 &&
- N0.getValueType() == MVT::i64) {
+ N0.getValueType() == MVT::i64 &&
+ (!(C->getZExtValue() & 0x80000000) ||
+ HasNoSignedComparisonUses(Node))) {
SDValue Imm = CurDAG->getTargetConstant(C->getZExtValue(), MVT::i32);
SDValue Reg = N0.getNode()->getOperand(0);