Revert r289955 and r289962. This is causing lots of ASAN failures for us.

Not sure whether it causes and ASAN false positive or whether it
actually leads to incorrect code or whether it even exposes bad code.
Hans, I'll get you instructions to reproduce this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@290066 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index e29c7cd6e3b452d0cf92e0fafd3b2e63576e9276..1470952f176a573ea18a7f060344d628172fb33a 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -28985,19 +28985,11 @@ static SDValue combineSelect(SDNode *N, SelectionDAG &DAG,
   return SDValue();
 }
 
-/// Combine brcond/cmov/setcc/.. based on comparing the result of
-/// atomic_load_add to use EFLAGS produced by the addition
-/// directly if possible. For example:
-///
-///   (setcc (cmp (atomic_load_add x, -C) C), COND_E)
-/// becomes:
-///   (setcc (LADD x, -C), COND_E)
-///
-/// and
+/// Combine:
 ///   (brcond/cmov/setcc .., (cmp (atomic_load_add x, 1), 0), COND_S)
-/// becomes:
+/// to:
 ///   (brcond/cmov/setcc .., (LADD x, 1), COND_LE)
-///
+/// i.e., reusing the EFLAGS produced by the LOCKed instruction.
 /// Note that this is only legal for some op/cc combinations.
 static SDValue combineSetCCAtomicArith(SDValue Cmp, X86::CondCode &CC,
                                        SelectionDAG &DAG) {
@@ -29006,7 +28998,7 @@ static SDValue combineSetCCAtomicArith(SDValue Cmp, X86::CondCode &CC,
         (Cmp.getOpcode() == X86ISD::SUB && !Cmp->hasAnyUseOfValue(0))))
     return SDValue();
 
-  // This applies to variations of the common case:
+  // This only applies to variations of the common case:
   //   (icmp slt x, 0) -> (icmp sle (add x, 1), 0)
   //   (icmp sge x, 0) -> (icmp sgt (add x, 1), 0)
   //   (icmp sle x, 0) -> (icmp slt (sub x, 1), 0)
@@ -29025,9 +29017,8 @@ static SDValue combineSetCCAtomicArith(SDValue Cmp, X86::CondCode &CC,
     return SDValue();
 
   auto *CmpRHSC = dyn_cast<ConstantSDNode>(CmpRHS);
-  if (!CmpRHSC)
+  if (!CmpRHSC || CmpRHSC->getZExtValue() != 0)
     return SDValue();
-  APInt Comparand = CmpRHSC->getAPIntValue();
 
   const unsigned Opc = CmpLHS.getOpcode();
 
@@ -29043,19 +29034,16 @@ static SDValue combineSetCCAtomicArith(SDValue Cmp, X86::CondCode &CC,
   if (Opc == ISD::ATOMIC_LOAD_SUB)
     Addend = -Addend;
 
-  if (Comparand == -Addend) {
-    // No change to CC.
-  } else if (CC == X86::COND_S && Comparand == 0 && Addend == 1) {
+  if (CC == X86::COND_S && Addend == 1)
     CC = X86::COND_LE;
-  } else if (CC == X86::COND_NS && Comparand == 0 && Addend == 1) {
+  else if (CC == X86::COND_NS && Addend == 1)
     CC = X86::COND_G;
-  } else if (CC == X86::COND_G && Comparand == 0 && Addend == -1) {
+  else if (CC == X86::COND_G && Addend == -1)
     CC = X86::COND_GE;
-  } else if (CC == X86::COND_LE && Comparand == 0 && Addend == -1) {
+  else if (CC == X86::COND_LE && Addend == -1)
     CC = X86::COND_L;
-  } else {
+  else
     return SDValue();
-  }
 
   SDValue LockOp = lowerAtomicArithWithLOCK(CmpLHS, DAG);
   DAG.ReplaceAllUsesOfValueWith(CmpLHS.getValue(0),

diff --git a/test/CodeGen/X86/atomic-eflags-reuse.ll b/test/CodeGen/X86/atomic-eflags-reuse.ll
index 80215639ae55137da827044f2e783e74b74b6608..dc1814b55cd3f1cda82ad817d63b274f969361b3 100644 (file)
--- a/test/CodeGen/X86/atomic-eflags-reuse.ll
+++ b/test/CodeGen/X86/atomic-eflags-reuse.ll
@@ -176,45 +176,4 @@ entry:
   ret i8 %tmp2
 }
 
-define i8 @test_sub_1_setcc_eq(i64* %p) #0 {
-; CHECK-LABEL: test_sub_1_setcc_eq:
-; CHECK:       # BB#0: # %entry
-; CHECK-NEXT:    lock decq (%rdi)
-; CHECK-NEXT:    sete %al
-; CHECK-NEXT:    retq
-entry:
-  %tmp0 = atomicrmw sub i64* %p, i64 1 seq_cst
-  %tmp1 = icmp eq i64 %tmp0, 1
-  %tmp2 = zext i1 %tmp1 to i8
-  ret i8 %tmp2
-}
-
-define i8 @test_add_5_setcc_ne(i64* %p) #0 {
-; CHECK-LABEL: test_add_5_setcc_ne:
-; CHECK:       # BB#0: # %entry
-; CHECK-NEXT:    lock addq $5, (%rdi)
-; CHECK-NEXT:    setne %al
-; CHECK-NEXT:    retq
-entry:
-  %tmp0 = atomicrmw add i64* %p, i64 5 seq_cst
-  %tmp1 = icmp ne i64 %tmp0, -5
-  %tmp2 = zext i1 %tmp1 to i8
-  ret i8 %tmp2
-}
-
-define i8 @test_add_5_setcc_ne_comparand_mismatch(i64* %p) #0 {
-; CHECK-LABEL: test_add_5_setcc_ne_comparand_mismatch:
-; CHECK:       # BB#0: # %entry
-; CHECK-NEXT:    movl $5, %eax
-; CHECK-NEXT:    lock xaddq %rax, (%rdi)
-; CHECK-NEXT:    testq %rax, %rax
-; CHECK-NEXT:    setne %al
-; CHECK-NEXT:    retq
-entry:
-  %tmp0 = atomicrmw add i64* %p, i64 5 seq_cst
-  %tmp1 = icmp ne i64 %tmp0, 0
-  %tmp2 = zext i1 %tmp1 to i8
-  ret i8 %tmp2
-}
-
 attributes #0 = { nounwind }