[SystemZ] Fix addcarry of usubo (PR42512)

Only custom lower uaddo+addcarry or usubo+subcarry chains and leave
mixtures like usubo+addcarry or uaddo+subcarry to the generic
legalizer. Otherwise we run into issues because SystemZ uses
different CC values for carries and borrows.

Fixes https://bugs.llvm.org/show_bug.cgi?id=42512.

Differential Revision: https://reviews.llvm.org/D64213

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@365242 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/SystemZ/SystemZISelLowering.cpp b/lib/Target/SystemZ/SystemZISelLowering.cpp
index 4dc2a808db767767b655bbd594274e378995ca05..56ec3a5b588d14d7eaccd9a9bc25c5630ec2f9cc 100644 (file)
--- a/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -3449,11 +3449,17 @@ SDValue SystemZTargetLowering::lowerADDSUBCARRY(SDValue Op,
   switch (Op.getOpcode()) {
   default: llvm_unreachable("Unknown instruction!");
   case ISD::ADDCARRY:
+    if (Carry.getOpcode() != ISD::UADDO && Carry.getOpcode() != ISD::ADDCARRY)
+      return SDValue();
+
     BaseOp = SystemZISD::ADDCARRY;
     CCValid = SystemZ::CCMASK_LOGICAL;
     CCMask = SystemZ::CCMASK_LOGICAL_CARRY;
     break;
   case ISD::SUBCARRY:
+    if (Carry.getOpcode() != ISD::USUBO && Carry.getOpcode() != ISD::SUBCARRY)
+      return SDValue();
+
     BaseOp = SystemZISD::SUBCARRY;
     CCValid = SystemZ::CCMASK_LOGICAL;
     CCMask = SystemZ::CCMASK_LOGICAL_BORROW;

diff --git a/test/CodeGen/SystemZ/pr42512.ll b/test/CodeGen/SystemZ/pr42512.ll
new file mode 100644 (file)
index 0000000..3131d69
--- /dev/null
+++ b/test/CodeGen/SystemZ/pr42512.ll
@@ -0,0 +1,23 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
+
+define i8 @test(i8 %x) {
+; CHECK-LABEL: test:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    slgfi %r0, 1
+; CHECK-NEXT:    ipm %r0
+; CHECK-NEXT:    afi %r0, -536870912
+; CHECK-NEXT:    srl %r0, 31
+; CHECK-NEXT:    ar %r2, %r0
+; CHECK-NEXT:    br %r14
+  %usubo = tail call { i64, i1 } @llvm.usub.with.overflow.i64(i64 undef, i64 1)
+  %ov = extractvalue { i64, i1 } %usubo, 1
+  %ovext = zext i1 %ov to i8
+  %ret = add i8 %x, %ovext
+  ret i8 %ret
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare { i64, i1 } @llvm.usub.with.overflow.i64(i64, i64) #0
+
+attributes #0 = { nounwind readnone speculatable }